Merge branch 'master' into rdmarsh/cpp/hasGlobalOrStdName

.codeqlmanifest.json

@@ -0,0 +1,5 @@
+{ "provide": [ "*/ql/src/qlpack.yml",
+               "*/upgrades/qlpack.yml",
+               "misc/legacy-support/*/qlpack.yml",
+               "misc/suite-helpers/qlpack.yml",
+               "codeql/.codeqlmanifest.json" ] }

.github/ISSUE_TEMPLATE/ql---general.md

@@ -0,0 +1,14 @@
+---
+name: General issue
+about: Tell us if you think something is wrong or if you have a question
+title: General issue
+labels: question
+assignees: ''
+
+---
+
+**Description of the issue**
+
+<!-- Please explain briefly what is the problem.
+If it is about an LGTM project, please include its URL.-->
+

.gitignore

@@ -12,3 +12,6 @@
 # Visual studio temporaries, except a file used by QL4VS
 .vs/*
 !.vs/VSWorkspaceSettings.json
+
+# It's useful (though not required) to be able to unpack codeql in the ql checkout itself
+/codeql/

CODEOWNERS

@@ -2,9 +2,9 @@
 /java/ @Semmle/java
 /javascript/ @Semmle/js
 /cpp/ @Semmle/cpp-analysis
-/cpp/**/*.qhelp @semmledocs-ac
+/cpp/**/*.qhelp @hubwriter
 /csharp/**/*.qhelp @jf205
-/java/**/*.qhelp @felicity-semmle
-/javascript/**/*.qhelp @mc-semmle
-/python/**/*.qhelp @felicity-semmle
-/docs/language/ @felicity-semmle @jf205
+/java/**/*.qhelp @felicitymay
+/javascript/**/*.qhelp @mchammer01
+/python/**/*.qhelp @felicitymay
+/docs/language/ @shati-patel @jf205

change-notes/1.22/analysis-javascript.md

@@ -36,6 +36,7 @@
 | Shift out of range (`js/shift-out-of-range`| Fewer false positive results | This rule now correctly handles BigInt shift operands. |
 | Superfluous trailing arguments (`js/superfluous-trailing-arguments`) | Fewer false-positive results. | This rule no longer flags calls to placeholder functions that trivially throw an exception. |
 | Undocumented parameter (`js/jsdoc/missing-parameter`) | No changes to results | This rule is now run on LGTM, although its results are still not shown by default. |
+| Missing space in string concatenation (`js/missing-space-in-concatenation`) | Fewer false positive results | The rule now requires a word-like part exists in the string concatenation. | 
 
 ## Changes to QL libraries
 

change-notes/1.23/analysis-cpp.md

@@ -18,8 +18,11 @@ The following changes in version 1.23 affect C/C++ analysis in all applications.
 | Hard-coded Japanese era start date in call (`cpp/japanese-era/constructor-or-method-with-exact-era-date`) | Deprecated | This query has been deprecated.  Use the new combined query Hard-coded Japanese era start date (`cpp/japanese-era/exact-era-date`) instead. |
 | Hard-coded Japanese era start date in struct (`cpp/japanese-era/struct-with-exact-era-date`) | Deprecated | This query has been deprecated.  Use the new combined query Hard-coded Japanese era start date (`cpp/japanese-era/exact-era-date`) instead. |
 | Hard-coded Japanese era start date (`cpp/japanese-era/exact-era-date`) | More correct results | This query now checks for the beginning date of the Reiwa era (1st May 2019). |
+| Sign check of bitwise operation (`cpp/bitwise-sign-check`) | Fewer false positive results | Results involving `>=` or `<=` are no longer reported. |
 | Too few arguments to formatting function (`cpp/wrong-number-format-arguments`) | Fewer false positive results | Fixed false positives resulting from mistmatching declarations of a formatting function. |
 | Too many arguments to formatting function (`cpp/too-many-format-arguments`) | Fewer false positive results | Fixed false positives resulting from mistmatching declarations of a formatting function. |
+| Unclear comparison precedence (`cpp/comparison-precedence`) | Fewer false positive results | False positives involving template classes and functions have been fixed. |
+| Comparison of narrow type with wide type in loop condition (`cpp/comparison-with-wider-type`) | Higher precision | The precision of this query has been increased to "high" as the alerts from this query have proved to be valuable on real-world projects. With this precision, results are now displayed by default in LGTM. |
 
 ## Changes to QL libraries
 
@@ -30,11 +33,16 @@ The following changes in version 1.23 affect C/C++ analysis in all applications.
   picture of the partial flow paths from a given source. The feature is
   disabled by default and can be enabled for individual configurations by
   overriding `int explorationLimit()`.
+* The data-flow library now supports flow out of C++ reference parameters.
 * The data-flow library now allows flow through the address-of operator (`&`).
 * The `DataFlow::DefinitionByReferenceNode` class now considers `f(x)` to be a
   definition of `x` when `x` is a variable of pointer type. It no longer
   considers deep paths such as `f(&x.myField)` to be definitions of `x`. These
   changes are in line with the user expectations we've observed.
+* The data-flow library now makes it easier to specify barriers/sanitizers
+  arising from guards by overriding the predicate
+  `isBarrierGuard`/`isSanitizerGuard` on data-flow and taint-tracking
+  configurations respectively.
 * There is now a `DataFlow::localExprFlow` predicate and a
   `TaintTracking::localExprTaint` predicate to make it easy to use the most
   common case of local data flow and taint: from one `Expr` to another.
@@ -44,3 +52,12 @@ The following changes in version 1.23 affect C/C++ analysis in all applications.
   predicates should be updated to use the corresponding new member predicate.
 * The predicates `Declaration.hasStdName()` and `Declaration.hasGlobalOrStdName`
   have been added, simplifying handling of C++ standard library functions.
+* The control-flow graph is now computed in QL, not in the extractor. This can
+  lead to regressions (or improvements) in how queries are optimized because
+  optimization in QL relies on static size estimates, and the control-flow edge
+  relations will now have different size estimates than before.
+* Support has been added for non-type template arguments.  This means that the
+  return type of `Declaration::getTemplateArgument()` and
+  `Declaration::getATemplateArgument` have changed to `Locatable`.  See the
+  documentation for `Declaration::getTemplateArgument()` and
+  `Declaration::getTemplateArgumentKind()` for details.

change-notes/1.23/analysis-csharp.md

@@ -8,6 +8,7 @@ The following changes in version 1.23 affect C# analysis in all applications.
 
 | **Query**                   | **Tags**  | **Purpose**                                                        |
 |-----------------------------|-----------|--------------------------------------------------------------------|
+| Deserialized delegate (`cs/deserialized-delegate`) | security, external/cwe/cwe-502 | Finds unsafe deserialization of delegate types. |
 | Unsafe year argument for 'DateTime' constructor (`cs/unsafe-year-construction`) | reliability, date-time | Finds incorrect manipulation of `DateTime` values, which could lead to invalid dates. |
 | Mishandling the Japanese era start date (`cs/mishandling-japanese-era`) | reliability, date-time | Finds hard-coded Japanese era start dates that could be invalid. |
 
@@ -16,6 +17,7 @@ The following changes in version 1.23 affect C# analysis in all applications.
 | **Query**                    | **Expected impact**    | **Change**                        |
 |------------------------------|------------------------|-----------------------------------|
 | Dereferenced variable may be null (`cs/dereferenced-value-may-be-null`) | Fewer false positive results | More `null` checks are now taken into account, including `null` checks for `dynamic` expressions and `null` checks such as `object alwaysNull = null; if (x != alwaysNull) ...`. |
+| Missing Dispose call on local IDisposable (`cs/local-not-disposed`) | Fewer false positive results | The query has been rewritten in order to identify more dispose patterns. For example, a local `IDisposable` that is disposed of by passing through a fluent API is no longer reported. |
 
 ## Removal of old queries
 
@@ -38,5 +40,10 @@ The following changes in version 1.23 affect C# analysis in all applications.
   disabled by default and can be enabled for individual configurations by
   overriding `int explorationLimit()`.
 * `foreach` statements where the body is guaranteed to be executed at least once, such as `foreach (var x in new string[]{ "a", "b", "c" }) { ... }`, are now recognized by all analyses based on the control flow graph (such as SSA, data flow and taint tracking).
+* Fixed the control flow graph for `switch` statements where the `default` case was not the last case. This had caused the remaining cases to be unreachable. `SwitchStmt.getCase(int i)` now puts the `default` case last.
+* There is now a `DataFlow::localExprFlow` predicate and a
+  `TaintTracking::localExprTaint` predicate to make it easy to use the most
+  common case of local data flow and taint: from one `Expr` to another.
+* Data is now tracked through null-coalescing expressions (`??`).
 
 ## Changes to autobuilder

change-notes/1.23/analysis-java.md

@@ -2,14 +2,22 @@
 
 The following changes in version 1.23 affect Java analysis in all applications.
 
+## New queries
+
+| **Query**                   | **Tags**  | **Purpose**                                                        |
+|-----------------------------|-----------|--------------------------------------------------------------------|
+| Continue statement that does not continue (`java/continue-in-false-loop`) | correctness | Finds `continue` statements in `do { ... } while (false)` loops. |
+
 ## Changes to existing queries
 
 | **Query**                    | **Expected impact**    | **Change**                        |
 |------------------------------|------------------------|-----------------------------------|
 | Dereferenced variable may be null (`java/dereferenced-value-may-be-null`) | Fewer false positives | Certain indirect null guards involving two auxiliary variables known to be equal can now be detected. |
+| Non-synchronized override of synchronized method (`java/non-sync-override`) | Fewer false positives | Results are now only reported if the immediately overridden method is synchronized. |
 | Query built from user-controlled sources (`java/sql-injection`) | More results | The query now identifies arguments to `Statement.executeLargeUpdate` and `Connection.prepareCall` as SQL expressions sinks. |
 | Query built from local-user-controlled sources (`java/sql-injection-local`) | More results | The query now identifies arguments to `Statement.executeLargeUpdate` and `Connection.prepareCall` as SQL expressions sinks. |
 | Query built without neutralizing special characters (`java/concatenated-sql-query`) | More results | The query now identifies arguments to `Statement.executeLargeUpdate` and `Connection.prepareCall` as SQL expressions sinks. |
+| Useless comparison test (`java/constant-comparison`) | Fewer false positives | Additional overflow check patterns are now recognized and no longer reported. |
 
 ## Changes to QL libraries
 

change-notes/1.23/analysis-javascript.md

@@ -2,6 +2,8 @@
 
 ## General improvements
 
+* Support for `globalThis` has been added.
+
 * Support for the following frameworks and libraries has been improved:
   - [firebase](https://www.npmjs.com/package/firebase)
   - [mongodb](https://www.npmjs.com/package/mongodb)
@@ -10,17 +12,28 @@
 
 * The call graph has been improved to resolve method calls in more cases. This may produce more security alerts.
 
+* TypeScript 3.6 and 3.7 features are now supported.
+
+* Automatic classification of generated files has been improved, in particular files generated by Doxygen are now recognized.
+
 ## New queries
 
 | **Query**                                                                 | **Tags**                                                          | **Purpose**                                                                                                                                                                            |
 |---------------------------------------------------------------------------|-------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | Unused index variable (`js/unused-index-variable`)                        | correctness                                                       | Highlights loops that iterate over an array, but do not use the index variable to access array elements, indicating a possible typo or logic error. Results are shown on LGTM by default. |
-| Loop bound injection (`js/loop-bound-injection`)                          | security, external/cwe/cwe-834                                      | Highlights loops where a user-controlled object with an arbitrary .length value can trick the server to loop indefinitely. Results are not shown on LGTM by default. |
+| Loop bound injection (`js/loop-bound-injection`)                          | security, external/cwe/cwe-834                                      | Highlights loops where a user-controlled object with an arbitrary .length value can trick the server to loop indefinitely. Results are shown on LGTM by default. |
+| Suspicious method name (`js/suspicious-method-name-declaration`)          | correctness, typescript, methods                                  | Highlights suspiciously named methods where the developer likely meant to write a constructor or function. Results are shown on LGTM by default. |
+| Shell command built from environment values (`js/shell-command-injection-from-environment`) | correctness, security, external/cwe/cwe-078, external/cwe/cwe-088 | Highlights shell commands that may change behavior inadvertently depending on the execution environment, indicating a possible violation of [CWE-78](https://cwe.mitre.org/data/definitions/78.html). Results are shown on LGTM by default.|
+| Use of returnless function (`js/use-of-returnless-function`)              | maintainability, correctness                                      | Highlights calls where the return value is used, but the callee never returns a value. Results are shown on LGTM by default. |
+| Useless regular expression character escape (`js/useless-regexp-character-escape`) | correctness, security, external/cwe/cwe-20 | Highlights regular expression strings with useless character escapes, indicating a possible violation of [CWE-20](https://cwe.mitre.org/data/definitions/20.html). Results are shown on LGTM by default. |
+| Unreachable method overloads (`js/unreachable-method-overloads`)          | correctness, typescript                                           | Highlights method overloads that are impossible to use from client code. Results are shown on LGTM by default. |
+| Ignoring result from pure array method (`js/ignore-array-result`)         | maintainability, correctness                                      | Highlights calls to array methods without side effects where the return value is ignored. Results are shown on LGTM by default. |
 
 ## Changes to existing queries
 
 | **Query**                      | **Expected impact**          | **Change**                                                                |
 |--------------------------------|------------------------------|---------------------------------------------------------------------------|
+| Double escaping or unescaping (`js/double-escaping`) | More results | This rule now detects additional escaping and unescaping functions. |
 | Incomplete string escaping or encoding (`js/incomplete-sanitization`) | Fewer false-positive results | This rule now recognizes additional ways delimiters can be stripped away. |
 | Client-side cross-site scripting (`js/xss`) | More results, fewer false-positive results | More potential vulnerabilities involving functions that manipulate DOM attributes are now recognized, and more sanitizers are detected. |
 | Code injection (`js/code-injection`) | More results | More potential vulnerabilities involving functions that manipulate DOM event handler attributes are now recognized. |
@@ -33,7 +46,27 @@
 | Reflected cross-site scripting (`js/reflected-xss`) | Fewer false-positive results | The query now recognizes more sanitizers. |
 | Stored cross-site scripting (`js/stored-xss`) | Fewer false-positive results | The query now recognizes more sanitizers. |
 | Uncontrolled command line (`js/command-line-injection`) | More results | This query now treats responses from servers as untrusted. |
+| Uncontrolled data used in path expression (`js/path-injection`) | Fewer false-positive results | This query now recognizes calls to Express `sendFile` as safe in some cases. |
+| Unknown directive (`js/unknown-directive`) | Fewer false positive results | This query no longer flags uses of ":", which is sometimes used like a directive. |
 
 ## Changes to QL libraries
 
 * `Expr.getDocumentation()` now handles chain assignments.
+
+## Removal of deprecated queries
+
+The following queries (deprecated since 1.17) are no longer available in the distribution:
+
+* Builtin redefined (js/builtin-redefinition)
+* Inefficient method definition (js/method-definition-in-constructor)
+* Bad parity check (js/incomplete-parity-check)
+* Potentially misspelled property or variable name (js/wrong-capitalization)
+* Unknown JSDoc tag (js/jsdoc/unknown-tag-type)
+* Invalid JSLint directive (js/jslint/invalid-directive)
+* Malformed JSLint directive (js/jslint/malformed-directive)
+* Use of HTML comments (js/html-comment)
+* Multi-line string literal (js/multi-line-string)
+* Octal literal (js/octal-literal)
+* Reserved word used as variable name (js/use-of-reserved-word)
+* Trailing comma in array or object expressions (js/trailing-comma-in-array-or-object)
+* Call to parseInt without radix (js/parseint-without-radix)

change-notes/1.23/analysis-python.md

@@ -11,4 +11,17 @@
 |-----------|----------|-------------|
 | Clear-text logging of sensitive information (`py/clear-text-logging-sensitive-data`) | security, external/cwe/cwe-312 | Finds instances where sensitive information is logged without encryption or hashing. Results are shown on LGTM by default. |
 | Clear-text storage of sensitive information (`py/clear-text-storage-sensitive-data`) | security, external/cwe/cwe-312 | Finds instances where sensitive information is stored without encryption or hashing. Results are shown on LGTM by default. |
+| Binding a socket to all network interfaces (`py/bind-socket-all-network-interfaces`) | security | Finds instances where a socket is bound to all network interfaces. Results are shown on LGTM by default. |
 
+
+## Changes to existing queries
+
+| **Query**                  | **Expected impact**    | **Change** |
+|----------------------------|------------------------|------------|
+| Unreachable code | Fewer false positives | Analysis now accounts for uses of `contextlib.suppress` to suppress exceptions. |
+| `__iter__` method returns a non-iterator | Better alert message | Alert now highlights which class is expected to be an iterator. |
+
+
+## Changes to QL libraries
+
+* Django library now recognizes positional arguments from a `django.conf.urls.url` regex (Django version 1.x)

change-notes/1.23/extractor-javascript.md

@@ -5,6 +5,19 @@
 ## Changes to code extraction
 
 * Asynchronous generator methods are now parsed correctly and no longer cause a spurious syntax error.
+* Files in `node_modules` and `bower_components` folders are no longer extracted by default. If you still want to extract files from these folders, you can add the following filters to your `lgtm.yml` file (or add them to existing filters):
+
+```yaml
+extraction:
+  javascript:
+    index:
+      filters:
+        - include: "**/node_modules"
+        - include: "**/bower_components"
+```
+
 * Recognition of CommonJS modules has improved. As a result, some files that were previously extracted as
   global scripts are now extracted as modules.
 * Top-level `await` is now supported.
+* A bug was fixed in how the TypeScript extractor handles default-exported anonymous classes.
+* A bug was fixed in how the TypeScript extractor handles computed instance field names.

change-notes/support/README.md

@@ -3,4 +3,4 @@
 Now that all of the QL documentation is in this repository,
 notes on the languages, compilers, and frameworks supported have moved.
 They're now stored as part of the Sphinx ``support`` project with the other documentation:
-``docs/ql-documentation/support``.
+``docs/language/support``.

config/identical-files.json

@@ -76,7 +76,11 @@
     "cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/Operand.qll",
     "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Operand.qll",
     "csharp/ql/src/semmle/code/csharp/ir/implementation/raw/Operand.qll",
-    "csharp/ql/src/semmle/code/csharp/ir/implementation/unaliased_ssa/Operand.qll"
+    "csharp/ql/src/semmle/code/csharp/ir/implementation/unaliased_ssa/Operand.qll" 
+  ],
+  "IR IRType": [
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/IRType.qll",
+    "csharp/ql/src/semmle/code/csharp/ir/implementation/IRType.qll"
   ],
   "IR Operand Tag": [
     "cpp/ql/src/semmle/code/cpp/ir/implementation/internal/OperandTag.qll",
@@ -169,22 +173,39 @@
     "cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/PrintIRImports.qll",
     "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/PrintIRImports.qll"
   ],
+  "C++ SSA SSAConstructionImports": [
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/SSAConstructionImports.qll",
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstructionImports.qll"
+  ],
   "C++ SSA AliasAnalysis": [
     "cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/AliasAnalysis.qll",
     "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasAnalysis.qll"
   ],
-  "C++ SSA SSAConstruction": [
+  "C++ IR ValueNumberingImports": [
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/raw/gvn/internal/ValueNumberingImports.qll",
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/gvn/internal/ValueNumberingImports.qll",
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/gvn/internal/ValueNumberingImports.qll"
+  ],
+  "IR SSA SimpleSSA": [
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/SimpleSSA.qll",
+    "csharp/ql/src/semmle/code/csharp/ir/implementation/unaliased_ssa/internal/SimpleSSA.qll"
+  ],
+  "IR SSA SSAConstruction": [
     "cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/SSAConstruction.qll",
-    "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstruction.qll"
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstruction.qll",
+    "csharp/ql/src/semmle/code/csharp/ir/implementation/unaliased_ssa/internal/SSAConstruction.qll"
   ],
-  "C++ SSA PrintSSA": [
+  "IR SSA PrintSSA": [
     "cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/PrintSSA.qll",
-    "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/PrintSSA.qll"
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/PrintSSA.qll",
+    "csharp/ql/src/semmle/code/csharp/ir/implementation/unaliased_ssa/internal/PrintSSA.qll"
   ],
-  "C++ IR ValueNumber": [
+  "IR ValueNumber": [
     "cpp/ql/src/semmle/code/cpp/ir/implementation/raw/gvn/ValueNumbering.qll",
     "cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/gvn/ValueNumbering.qll",
-    "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/gvn/ValueNumbering.qll"
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/gvn/ValueNumbering.qll",
+    "csharp/ql/src/semmle/code/csharp/ir/implementation/raw/gvn/ValueNumbering.qll",
+    "csharp/ql/src/semmle/code/csharp/ir/implementation/unaliased_ssa/gvn/ValueNumbering.qll"
   ],
   "C++ IR ConstantAnalysis": [
     "cpp/ql/src/semmle/code/cpp/ir/implementation/raw/constant/ConstantAnalysis.qll",
@@ -235,5 +256,9 @@
   "C# IR PrintIRImports": [
     "csharp/ql/src/semmle/code/csharp/ir/implementation/raw/internal/PrintIRImports.qll",
     "csharp/ql/src/semmle/code/csharp/ir/implementation/unaliased_ssa/internal/PrintIRImports.qll"
+  ],
+  "C# IR ValueNumberingImports": [
+    "csharp/ql/src/semmle/code/csharp/ir/implementation/raw/gvn/internal/ValueNumberingImports.qll",
+    "csharp/ql/src/semmle/code/csharp/ir/implementation/unaliased_ssa/gvn/internal/ValueNumberingImports.qll"
   ]
 }

cpp/ql/src/Best Practices/Unused Entities/UnusedStaticVariables.ql

@@ -21,6 +21,7 @@ from Variable v
 where
   v.isStatic() and
   v.hasDefinition() and
+  not v.isConstexpr() and
   not exists(VariableAccess a | a.getTarget() = v) and
   not v instanceof MemberVariable and
   not declarationHasSideEffects(v) and

cpp/ql/src/Likely Bugs/Arithmetic/BadAdditionOverflowCheck.qhelp

@@ -2,36 +2,39 @@
   "-//Semmle//qhelp//EN"
   "qhelp.dtd">
 <qhelp>
-  <overview>
-    <p>
-      Checking for overflow of integer addition needs to be done with
-      care, because automatic type promotion can prevent the check
-      from working correctly.
-    </p>
-  </overview>
-  <recommendation>
-    <p>
-      Use an explicit cast to make sure that the result of the addition is
-      not implicitly converted to a larger type.
-    </p>
-  </recommendation>
-  <example>
-    <sample src="BadAdditionOverflowCheckExample1.cpp" />
-    <p>
-      On a typical architecture where <tt>short</tt> is 16 bits
-      and <tt>int</tt> is 32 bits, the operands of the addition are
-      automatically promoted to <tt>int</tt>, so it cannot overflow
-      and the result of the comparison is always false.
-    </p>
-    <p>
-      The code below implements the check correctly, by using an
-      explicit cast to make sure that the result of the addition
-      is <tt>unsigned short</tt>.
-    </p>
-    <sample src="BadAdditionOverflowCheckExample2.cpp" />
-  </example>
-  <references>
-    <li><a href="http://c-faq.com/expr/preservingrules.html">Preserving Rules</a></li>
-    <li><a href="https://www.securecoding.cert.org/confluence/plugins/servlet/mobile#content/view/20086942">Understand integer conversion rules</a></li>
-  </references>
+
+<overview>
+<p>
+Checking for overflow of integer addition needs to be done with
+care, because automatic type promotion can prevent the check
+from working as intended, with the same value (<code>true</code>
+or <code>false</code>) always being returned.
+</p>
+</overview>
+<recommendation>
+<p>
+Use an explicit cast to make sure that the result of the addition is
+not implicitly converted to a larger type.
+</p>
+</recommendation>
+<example>
+<sample src="BadAdditionOverflowCheckExample1.cpp" />
+<p>
+On a typical architecture where <code>short</code> is 16 bits
+and <code>int</code> is 32 bits, the operands of the addition are
+automatically promoted to <code>int</code>, so it cannot overflow
+and the result of the comparison is always false.
+</p>
+<p>
+The code below implements the check correctly, by using an
+explicit cast to make sure that the result of the addition
+is <code>unsigned short</code> (which may overflow, in which case
+the comparison would evaluate to <code>true</code>).
+</p>
+<sample src="BadAdditionOverflowCheckExample2.cpp" />
+</example>
+<references>
+<li><a href="http://c-faq.com/expr/preservingrules.html">Preserving Rules</a></li>
+<li><a href="https://www.securecoding.cert.org/confluence/plugins/servlet/mobile#content/view/20086942">Understand integer conversion rules</a></li>
+</references>
 </qhelp>

cpp/ql/src/Likely Bugs/Arithmetic/BadAdditionOverflowCheckExample1.cpp

@@ -1,3 +1,4 @@
 bool checkOverflow(unsigned short x, unsigned short y) {
-  return (x + y < x);  // BAD: x and y are automatically promoted to int.
+  // BAD: comparison is always false due to type promotion
+  return (x + y < x);  
 }

cpp/ql/src/Likely Bugs/Arithmetic/BitwiseSignCheck.ql

@@ -14,9 +14,16 @@ import cpp
 
 from RelationalOperation e, BinaryBitwiseOperation lhs
 where
-  lhs = e.getGreaterOperand() and
-  lhs.getActualType().(IntegralType).isSigned() and
-  forall(int op | op = lhs.(BitwiseAndExpr).getAnOperand().getValue().toInt() | op < 0) and
+  // `lhs > 0` (or `0 < lhs`)
+  // (note that `lhs < 0`, `lhs >= 0` or `lhs <= 0` all imply that the signedness of
+  //  `lhs` is understood, so should not be flagged).
+  (e instanceof GTExpr or e instanceof LTExpr) and
+  e.getGreaterOperand() = lhs and
   e.getLesserOperand().getValue() = "0" and
+  // lhs is signed
+  lhs.getActualType().(IntegralType).isSigned() and
+  // if `lhs` has the form `x & c`, with constant `c`, `c` is negative
+  forall(int op | op = lhs.(BitwiseAndExpr).getAnOperand().getValue().toInt() | op < 0) and
+  // exception for cases involving macros
   not e.isAffectedByMacro()
 select e, "Potential unsafe sign check of a bitwise operation."

cpp/ql/src/Likely Bugs/Arithmetic/ComparisonPrecedence.ql

@@ -14,5 +14,8 @@
 import cpp
 
 from ComparisonOperation co, ComparisonOperation chco
-where co.getAChild() = chco and not chco.isParenthesised()
-select co, "Check the comparison operator precedence."
+where
+  co.getAChild() = chco and
+  not chco.isParenthesised() and
+  not co.isFromUninstantiatedTemplate(_)
+select co, "Comparison as an operand to another comparison."

cpp/ql/src/Likely Bugs/Leap Year/LeapYear.qll

@@ -30,7 +30,7 @@ private predicate additionalLogicalCheck(Expr e, string operation, int valueToCh
 /**
  * An `Operation` that seems to be checking for leap year.
  */
-class CheckForLeapYearOperation extends Operation {
+class CheckForLeapYearOperation extends Expr {
   CheckForLeapYearOperation() {
     exists(BinaryArithmeticOperation bo | bo = this |
       bo.getAnOperand().getValue().toInt() = 4 and
@@ -39,8 +39,6 @@ class CheckForLeapYearOperation extends Operation {
       additionalLogicalCheck(this.getEnclosingElement(), "%", 400)
     )
   }
-
-  override string getOperator() { result = "LeapYearCheck" }
 }
 
 /**

cpp/ql/src/Likely Bugs/Memory Management/Buffer Overflow/BufferAccess.qll

@@ -0,0 +1,174 @@
+import cpp
+import semmle.code.cpp.dataflow.TaintTracking
+private import semmle.code.cpp.dataflow.RecursionPrevention
+
+/**
+ * A buffer which includes an allocation size.
+ */
+abstract class BufferWithSize extends DataFlow::Node {
+  abstract Expr getSizeExpr();
+
+  BufferAccess getAnAccess() {
+    any(BufferWithSizeConfig bsc).hasFlow(this, DataFlow::exprNode(result.getPointer()))
+  }
+}
+
+/** An allocation function. */
+abstract class Alloc extends Function { }
+
+/**
+ * Allocation functions identified by the QL for C/C++ standard library.
+ */
+class DefaultAlloc extends Alloc {
+  DefaultAlloc() { allocationFunction(this) }
+}
+
+/** A buffer created through a call to an allocation function. */
+class AllocBuffer extends BufferWithSize {
+  FunctionCall call;
+
+  AllocBuffer() {
+    asExpr() = call and
+    call.getTarget() instanceof Alloc
+  }
+
+  override Expr getSizeExpr() { result = call.getArgument(0) }
+}
+
+/**
+ * Find accesses of buffers for which we have a size expression.
+ */
+private class BufferWithSizeConfig extends TaintTracking::Configuration {
+  BufferWithSizeConfig() { this = "BufferWithSize" }
+
+  override predicate isSource(DataFlow::Node n) { n = any(BufferWithSize b) }
+
+  override predicate isSink(DataFlow::Node n) { n.asExpr() = any(BufferAccess ae).getPointer() }
+
+  override predicate isSanitizer(DataFlow::Node s) {
+    s = any(BufferWithSize b) and
+    s.asExpr().getControlFlowScope() instanceof Alloc
+  }
+}
+
+/**
+ * An access (read or write) to a buffer, provided as a pair of
+ * a pointer to the buffer and the length of data to be read or written.
+ * Extend this class to support different kinds of buffer access.
+ */
+abstract class BufferAccess extends Locatable {
+  /** Gets the pointer to the buffer being accessed. */
+  abstract Expr getPointer();
+
+  /** Gets the length of the data being read or written by this buffer access. */
+  abstract Expr getAccessedLength();
+}
+
+/**
+ * A buffer access through an array expression.
+ */
+class ArrayBufferAccess extends BufferAccess, ArrayExpr {
+  override Expr getPointer() { result = this.getArrayBase() }
+
+  override Expr getAccessedLength() { result = this.getArrayOffset() }
+}
+
+/**
+ * A buffer access through an overloaded array expression.
+ */
+class OverloadedArrayBufferAccess extends BufferAccess, OverloadedArrayExpr {
+  override Expr getPointer() { result = this.getQualifier() }
+
+  override Expr getAccessedLength() { result = this.getAnArgument() }
+}
+
+/**
+ * A buffer access through pointer arithmetic.
+ */
+class PointerArithmeticAccess extends BufferAccess, Expr {
+  PointerArithmeticOperation p;
+
+  PointerArithmeticAccess() {
+    this = p and
+    p.getAnOperand().getType().getUnspecifiedType() instanceof IntegralType and
+    not p.getParent() instanceof ComparisonOperation
+  }
+
+  override Expr getPointer() {
+    result = p.getAnOperand() and
+    result.getType().getUnspecifiedType() instanceof PointerType
+  }
+
+  override Expr getAccessedLength() {
+    result = p.getAnOperand() and
+    result.getType().getUnspecifiedType() instanceof IntegralType
+  }
+}
+
+/**
+ * A pair of buffer accesses through a call to memcpy.
+ */
+class MemCpy extends BufferAccess, FunctionCall {
+  MemCpy() { getTarget().hasName("memcpy") }
+
+  override Expr getPointer() {
+    result = getArgument(0) or
+    result = getArgument(1)
+  }
+
+  override Expr getAccessedLength() { result = getArgument(2) }
+}
+
+class StrncpySizeExpr extends BufferAccess, FunctionCall {
+  StrncpySizeExpr() { getTarget().hasName("strncpy") }
+
+  override Expr getPointer() {
+    result = getArgument(0) or
+    result = getArgument(1)
+  }
+
+  override Expr getAccessedLength() { result = getArgument(2) }
+}
+
+class RecvSizeExpr extends BufferAccess, FunctionCall {
+  RecvSizeExpr() { getTarget().hasName("recv") }
+
+  override Expr getPointer() { result = getArgument(1) }
+
+  override Expr getAccessedLength() { result = getArgument(2) }
+}
+
+class SendSizeExpr extends BufferAccess, FunctionCall {
+  SendSizeExpr() { getTarget().hasName("send") }
+
+  override Expr getPointer() { result = getArgument(1) }
+
+  override Expr getAccessedLength() { result = getArgument(2) }
+}
+
+class SnprintfSizeExpr extends BufferAccess, FunctionCall {
+  SnprintfSizeExpr() { getTarget().hasName("snprintf") }
+
+  override Expr getPointer() { result = getArgument(0) }
+
+  override Expr getAccessedLength() { result = getArgument(1) }
+}
+
+class MemcmpSizeExpr extends BufferAccess, FunctionCall {
+  MemcmpSizeExpr() { getTarget().hasName("Memcmp") }
+
+  override Expr getPointer() {
+    result = getArgument(0) or
+    result = getArgument(1)
+  }
+
+  override Expr getAccessedLength() { result = getArgument(2) }
+}
+
+class MallocSizeExpr extends BufferAccess, FunctionCall {
+  MallocSizeExpr() { getTarget().hasName("malloc") }
+
+  override Expr getPointer() { none() }
+
+  override Expr getAccessedLength() { result = getArgument(1) }
+}

cpp/ql/src/Likely Bugs/Memory Management/Buffer Overflow/NtohlArrayBad.cpp

@@ -0,0 +1,6 @@
+int get_number_from_network();
+
+int process_network(int[] buff, int buffSize) {
+  int i = ntohl(get_number_from_network());
+  return buff[i];
+}

cpp/ql/src/Likely Bugs/Memory Management/Buffer Overflow/NtohlArrayGood.cpp

@@ -0,0 +1,10 @@
+uint32_t get_number_from_network();
+
+int process_network(int[] buff, uint32_t buffSize) {
+  uint32_t i = ntohl(get_number_from_network());
+  if (i < buffSize) {
+    return buff[i];
+  } else {
+    return -1;
+  }
+}

cpp/ql/src/Likely Bugs/Memory Management/Buffer Overflow/NtohlArrayNoBound.qll

@@ -0,0 +1,33 @@
+import cpp
+import semmle.code.cpp.dataflow.DataFlow
+import semmle.code.cpp.controlflow.Guards
+import BufferAccess
+import semmle.code.cpp.valuenumbering.GlobalValueNumbering
+
+class NetworkFunctionCall extends FunctionCall {
+  NetworkFunctionCall() {
+    getTarget().hasName("ntohd") or
+    getTarget().hasName("ntohf") or
+    getTarget().hasName("ntohl") or
+    getTarget().hasName("ntohll") or
+    getTarget().hasName("ntohs")
+  }
+}
+
+class NetworkToBufferSizeConfiguration extends DataFlow::Configuration {
+  NetworkToBufferSizeConfiguration() { this = "NetworkToBufferSizeConfiguration" }
+
+  override predicate isSource(DataFlow::Node node) { node.asExpr() instanceof NetworkFunctionCall }
+
+  override predicate isSink(DataFlow::Node node) {
+    node.asExpr() = any(BufferAccess ba).getAccessedLength()
+  }
+
+  override predicate isBarrier(DataFlow::Node node) {
+    exists(GuardCondition gc, GVN gvn |
+      gc.getAChild*() = gvn.getAnExpr() and
+      globalValueNumber(node.asExpr()) = gvn and
+      gc.controls(node.asExpr().getBasicBlock(), _)
+    )
+  }
+}

cpp/ql/src/Likely Bugs/Memory Management/Buffer Overflow/NtohlArrayNoBoundOpenSource.qhelp

@@ -0,0 +1,54 @@
+<!DOCTYPE qhelp PUBLIC
+  "-//Semmle//qhelp//EN"
+  "qhelp.dtd">
+<qhelp>
+
+<overview>
+<p>
+Data received over a network connection may be received in a different byte order than
+the byte order used by the local host, making the data difficult to process. To address this,
+data received over the wire is usually converted to host byte order by a call to a network-to-host
+byte order function, such as <code>ntohl</code>.
+</p>
+<p>
+The use of a network-to-host byte order function is therefore a good indicator that the returned
+value is unvalidated data retrieved from the network, and should not be used without further
+validation. In particular, the returned value should not be used as an array index or array length
+value without validation, as this could result in a buffer overflow vulnerability.
+</p>
+</overview>
+
+<recommendation>
+<p>
+Validate data returned by network-to-host byte order functions before use and especially before
+using the value as an array index or bound.
+</p>
+</recommendation>
+
+<example>
+<p>In the example below, network data is retrieved and passed to <code>ntohl</code> to convert
+it to host byte order. The data is then used as an index in an array access expression. However,
+there is no validation that the data returned by <code>ntohl</code> is within the bounds of the array,
+which could lead to reading outside the bounds of the buffer.
+</p>
+<sample src="NtohlArrayBad.cpp" />
+<p>In the corrected example, the returned data is validated against the known size of the buffer,
+before being used as an array index.</p>
+<sample src="NtohlArrayGood.cpp" />
+</example>
+
+<references>
+<li>
+  <a href="https://docs.microsoft.com/en-us/windows/desktop/api/winsock/nf-winsock-ntohl">
+    ntohl - winsock reference
+  </a> 
+</li>
+<li>
+  <a href="https://linux.die.net/man/3/ntohl">
+    ntohl - Linux man page
+  </a> 
+</li>
+
+</references>
+
+</qhelp>

cpp/ql/src/Likely Bugs/Memory Management/Buffer Overflow/NtohlArrayNoBoundOpenSource.ql

@@ -0,0 +1,17 @@
+/**
+ * @id cpp/network-to-host-function-as-array-bound
+ * @name Untrusted network-to-host usage
+ * @description Using the result of a network-to-host byte order function, such as ntohl, as an
+ *              array bound or length value without checking it may result in buffer overflows or
+ *              other vulnerabilties.
+ * @kind problem
+ * @problem.severity error
+ */
+
+import cpp
+import NtohlArrayNoBound
+import semmle.code.cpp.dataflow.DataFlow
+
+from NetworkToBufferSizeConfiguration bufConfig, DataFlow::Node source, DataFlow::Node sink
+where bufConfig.hasFlow(source, sink)
+select sink, "Unchecked use of data from network function $@", source, source.toString()

cpp/ql/src/Likely Bugs/Protocols/boostorg/TlsSettingsMisconfiguration.qhelp

@@ -0,0 +1,15 @@
+<!DOCTYPE qhelp PUBLIC
+  "-//Semmle//qhelp//EN"
+  "qhelp.dtd">
+<qhelp>
+<overview>
+  <p>Using TLS or SSLv23 protool from the boost::asio library, but not disabling deprecated protocols or disabling minimum-recommended protocols.</p>
+</overview>
+
+<references>
+  <li>
+    <a href="https://www.boost.org/doc/libs/1_71_0/doc/html/boost_asio.html">Boost.Asio documentation</a>.
+  </li>
+</references>
+</qhelp>
+

cpp/ql/src/Likely Bugs/Protocols/boostorg/TlsSettingsMisconfiguration.ql

@@ -0,0 +1,119 @@
+/**
+ * @name Boost_asio TLS Settings Misconfiguration
+ * @description Using TLS or SSLv23 protool from the boost::asio library, but not disabling deprecated protocols or disabling minimum-recommended protocols
+ * @kind problem
+ * @problem.severity error
+ * @id cpp/boost/tls_settings_misconfiguration
+ * @tags security
+ */
+
+import cpp
+import semmle.code.cpp.security.boostorg.asio.protocols
+
+class ExistsAnyFlowConfig extends DataFlow::Configuration {
+  ExistsAnyFlowConfig() { this = "ExistsAnyFlowConfig" }
+
+  override predicate isSource(DataFlow::Node source) { any() }
+
+  override predicate isSink(DataFlow::Node sink) { any() }
+}
+
+bindingset[flag]
+predicate isOptionSet(ConstructorCall cc, int flag, FunctionCall fcSetOptions) {
+  exists(
+    BoostorgAsio::SslContextFlowsToSetOptionConfig config, ExistsAnyFlowConfig testConfig,
+    Expr optionsSink
+  |
+    config.hasFlow(DataFlow::exprNode(cc), DataFlow::exprNode(optionsSink)) and
+    exists(VariableAccess contextSetOptions |
+      testConfig.hasFlow(DataFlow::exprNode(cc), DataFlow::exprNode(contextSetOptions)) and
+      exists(BoostorgAsio::SslSetOptionsFunction f | f.getACallToThisFunction() = fcSetOptions |
+        contextSetOptions = fcSetOptions.getQualifier() and
+        forall(
+          Expr optionArgument, BoostorgAsio::SslOptionConfig optionArgConfig,
+          Expr optionArgumentSource
+        |
+          optionArgument = fcSetOptions.getArgument(0) and
+          optionArgConfig
+              .hasFlow(DataFlow::exprNode(optionArgumentSource), DataFlow::exprNode(optionArgument))
+        |
+          optionArgument.getValue().toInt().bitShiftRight(16).bitAnd(flag) = flag
+        )
+      )
+    )
+  )
+}
+
+bindingset[flag]
+predicate isOptionNotSet(ConstructorCall cc, int flag) {
+  not exists(
+    BoostorgAsio::SslContextFlowsToSetOptionConfig config, ExistsAnyFlowConfig testConfig,
+    Expr optionsSink
+  |
+    config.hasFlow(DataFlow::exprNode(cc), DataFlow::exprNode(optionsSink)) and
+    exists(VariableAccess contextSetOptions |
+      testConfig.hasFlow(DataFlow::exprNode(cc), DataFlow::exprNode(contextSetOptions)) and
+      exists(FunctionCall fcSetOptions, BoostorgAsio::SslSetOptionsFunction f |
+        f.getACallToThisFunction() = fcSetOptions
+      |
+        contextSetOptions = fcSetOptions.getQualifier() and
+        forall(
+          Expr optionArgument, BoostorgAsio::SslOptionConfig optionArgConfig,
+          Expr optionArgumentSource
+        |
+          optionArgument = fcSetOptions.getArgument(0) and
+          optionArgConfig
+              .hasFlow(DataFlow::exprNode(optionArgumentSource), DataFlow::exprNode(optionArgument))
+        |
+          optionArgument.getValue().toInt().bitShiftRight(16).bitAnd(flag) = flag
+        )
+      )
+    )
+  )
+}
+
+from
+  BoostorgAsio::SslContextCallTlsProtocolConfig configConstructor,
+  BoostorgAsio::SslContextFlowsToSetOptionConfig config, Expr protocolSource, Expr protocolSink,
+  ConstructorCall cc, Expr e, string msg
+where
+  configConstructor.hasFlow(DataFlow::exprNode(protocolSource), DataFlow::exprNode(protocolSink)) and
+  cc.getArgument(0) = protocolSink and
+  (
+    BoostorgAsio::isExprSslV23BoostProtocol(protocolSource) and
+    not exists(Expr optionsSink |
+      config.hasFlow(DataFlow::exprNode(cc), DataFlow::exprNode(optionsSink)) and
+      isOptionSet(cc, BoostorgAsio::getShiftedSslOptionsNoSsl3(), _) and
+      isOptionSet(cc, BoostorgAsio::getShiftedSslOptionsNoTls1(), _) and
+      isOptionSet(cc, BoostorgAsio::getShiftedSslOptionsNoTls1_1(), _) and
+      isOptionNotSet(cc, BoostorgAsio::getShiftedSslOptionsNoTls1_2())
+    )
+    or
+    BoostorgAsio::isExprTlsBoostProtocol(protocolSource) and
+    not BoostorgAsio::isExprSslV23BoostProtocol(protocolSource) and
+    not exists(Expr optionsSink |
+      config.hasFlow(DataFlow::exprNode(cc), DataFlow::exprNode(optionsSink)) and
+      isOptionSet(cc, BoostorgAsio::getShiftedSslOptionsNoTls1(), _) and
+      isOptionSet(cc, BoostorgAsio::getShiftedSslOptionsNoTls1_1(), _) and
+      isOptionNotSet(cc, BoostorgAsio::getShiftedSslOptionsNoTls1_2())
+    )
+  ) and
+  (
+    BoostorgAsio::isExprSslV23BoostProtocol(protocolSource) and
+    isOptionNotSet(cc, BoostorgAsio::getShiftedSslOptionsNoSsl3()) and
+    e = cc and
+    msg = "no_sslv3 has not been set"
+    or
+    isOptionNotSet(cc, BoostorgAsio::getShiftedSslOptionsNoTls1()) and
+    e = cc and
+    msg = "no_tlsv1 has not been set"
+    or
+    isOptionNotSet(cc, BoostorgAsio::getShiftedSslOptionsNoTls1_1()) and
+    e = cc and
+    msg = "no_tlsv1_1 has not been set"
+    or
+    isOptionSet(cc, BoostorgAsio::getShiftedSslOptionsNoTls1_2(), e) and
+    msg = "no_tlsv1_2 was set"
+  )
+select cc, "Usage of $@ with protocol $@ is not configured correctly: The option $@.", cc,
+  "boost::asio::ssl::context::context", protocolSource, protocolSource.toString(), e, msg

cpp/ql/src/Likely Bugs/Protocols/boostorg/UseOfDeprecatedHardcodedProtocol.qhelp

@@ -0,0 +1,16 @@
+<!DOCTYPE qhelp PUBLIC
+  "-//Semmle//qhelp//EN"
+  "qhelp.dtd">
+<qhelp>
+<overview>
+  <p>Using boost::asio library but specifying a deprecated hardcoded protocol.</p>
+  <p>Using a deprecated hardcoded protocol instead of negotiting would lock your application to a protocol that has known vulnerabilities or weaknesses.</p>
+</overview>
+
+<references>
+  <li>
+    <a href="https://www.boost.org/doc/libs/1_71_0/doc/html/boost_asio.html">Boost.Asio documentation</a>.
+  </li>
+</references>
+</qhelp>
+

cpp/ql/src/Likely Bugs/Protocols/boostorg/UseOfDeprecatedHardcodedProtocol.ql

@@ -0,0 +1,27 @@
+/**
+ * @name boost::asio Use of deprecated hardcoded Protocol
+ * @description Using a deprecated hard-coded protocol using the boost::asio library.
+ * @kind problem
+ * @problem.severity error
+ * @id cpp/boost/use-of-deprecated-hardcoded-security-protocol
+ * @tags security
+ */
+
+import cpp
+import semmle.code.cpp.security.boostorg.asio.protocols
+
+from
+  BoostorgAsio::SslContextCallConfig config, Expr protocolSource, Expr protocolSink,
+  ConstructorCall cc
+where
+  config.hasFlow(DataFlow::exprNode(protocolSource), DataFlow::exprNode(protocolSink)) and
+  not exists(BoostorgAsio::SslContextCallTlsProtocolConfig tlsConfig |
+    tlsConfig.hasFlow(DataFlow::exprNode(protocolSource), DataFlow::exprNode(protocolSink))
+  ) and
+  cc.getArgument(0) = protocolSink and
+  exists(BoostorgAsio::SslContextCallBannedProtocolConfig bannedConfig |
+    bannedConfig.hasFlow(DataFlow::exprNode(protocolSource), DataFlow::exprNode(protocolSink))
+  )
+select protocolSink, "Usage of $@ specifying a deprecated hardcoded protocol $@ in function $@.",
+  cc, "boost::asio::ssl::context::context", protocolSource, protocolSource.toString(),
+  cc.getEnclosingFunction(), cc.getEnclosingFunction().toString()

cpp/ql/src/Microsoft/SAL.qll

@@ -2,29 +2,45 @@ import cpp
 
 class SALMacro extends Macro {
   SALMacro() {
-    this.getFile().getBaseName() = "sal.h" or
-    this.getFile().getBaseName() = "specstrings_strict.h" or
-    this.getFile().getBaseName() = "specstrings.h"
+    exists(string filename | filename = this.getFile().getBaseName() |
+      filename = "sal.h" or
+      filename = "specstrings_strict.h" or
+      filename = "specstrings.h" or
+      filename = "w32p.h" or
+      filename = "minwindef.h"
+    ) and
+    (
+      // Dialect for Windows 8 and above
+      this.getName().matches("\\_%\\_")
+      or
+      // Dialect for Windows 7
+      this.getName().matches("\\_\\_%")
+    )
   }
 }
 
+pragma[noinline]
+predicate isTopLevelMacroAccess(MacroAccess ma) { not exists(ma.getParentInvocation()) }
+
 class SALAnnotation extends MacroInvocation {
   SALAnnotation() {
     this.getMacro() instanceof SALMacro and
-    not exists(this.getParentInvocation())
+    isTopLevelMacroAccess(this)
   }
 
   /** Returns the `Declaration` annotated by `this`. */
-  Declaration getDeclaration() { annotatesAt(this, result.getADeclarationEntry(), _, _) }
+  Declaration getDeclaration() {
+    annotatesAt(this, result.getADeclarationEntry(), _, _) and
+    not result instanceof Type // exclude typedefs
+  }
 
   /** Returns the `DeclarationEntry` annotated by `this`. */
-  DeclarationEntry getDeclarationEntry() { annotatesAt(this, result, _, _) }
+  DeclarationEntry getDeclarationEntry() {
+    annotatesAt(this, result, _, _) and
+    not result instanceof TypeDeclarationEntry // exclude typedefs
+  }
 }
 
-/*
- * Particular SAL annotations of interest
- */
-
 class SALCheckReturn extends SALAnnotation {
   SALCheckReturn() {
     exists(SALMacro m | m = this.getMacro() |
@@ -39,8 +55,8 @@ class SALNotNull extends SALAnnotation {
     exists(SALMacro m | m = this.getMacro() |
       not m.getName().matches("%\\_opt\\_%") and
       (
-        m.getName().matches("\\_In%") or
-        m.getName().matches("\\_Out%") or
+        m.getName().matches("_In%") or
+        m.getName().matches("_Out%") or
         m.getName() = "_Ret_notnull_"
       )
     ) and
@@ -63,42 +79,124 @@ class SALMaybeNull extends SALAnnotation {
   }
 }
 
-/*
- * Implementation details
+///////////////////////////////////////////////////////////////////////////////
+// Implementation details
+/**
+ * Holds if `a` annotates the declaration entry `d` and
+ * its start position is the `idx`th position in `file` that holds a SAL element.
  */
-
-private predicate annotatesAt(SALAnnotation a, DeclarationEntry e, File file, int idx) {
-  a = salElementAt(file, idx) and
-  (
-    // Base case: `a` right before `e`
-    e = salElementAt(file, idx + 1)
-    or
-    // Recursive case: `a` right before some annotation on `e`
-    annotatesAt(_, e, file, idx + 1)
-  )
-}
-
-library class SALElement extends Element {
-  SALElement() {
-    this instanceof DeclarationEntry or
-    this instanceof SALAnnotation
-  }
-}
-
-/** Gets the `idx`th `SALElement` in `file`. */
-private SALElement salElementAt(File file, int idx) {
-  interestingLoc(file, result, interestingStartPos(file, idx))
+predicate annotatesAt(SALAnnotation a, DeclarationEntry d, File file, int idx) {
+  annotatesAtPosition(a.(SALElement).getStartPosition(), d, file, idx)
 }
 
 /**
- * Holds if an SALElement element at character `result` comes at
- * position `idx` in `file`.
+ * Holds if `pos` is the `idx`th position in `file` that holds a SAL element,
+ * which annotates the declaration entry `d` (by occurring before it without
+ * any other declaration entries in between).
  */
-private int interestingStartPos(File file, int idx) {
-  result = rank[idx](int otherStart | interestingLoc(file, _, otherStart))
+// For performance reasons, do not mention the annotation itself here,
+// but compute with positions instead. This performs better on databases
+// with many annotations at the same position.
+private predicate annotatesAtPosition(SALPosition pos, DeclarationEntry d, File file, int idx) {
+  pos = salRelevantPositionAt(file, idx) and
+  salAnnotationPos(pos) and
+  (
+    // Base case: `pos` right before `d`
+    d.(SALElement).getStartPosition() = salRelevantPositionAt(file, idx + 1)
+    or
+    // Recursive case: `pos` right before some annotation on `d`
+    annotatesAtPosition(_, d, file, idx + 1)
+  )
 }
 
-/** Holds if `element` in `file` is at character `startPos`. */
-private predicate interestingLoc(File file, SALElement element, int startPos) {
-  element.getLocation().charLoc(file, startPos, _)
+/**
+ * A parameter annotated by one or more SAL annotations.
+ */
+class SALParameter extends Parameter {
+  /** One of this parameter's annotations. */
+  SALAnnotation a;
+
+  SALParameter() { annotatesAt(a, this.getADeclarationEntry(), _, _) }
+
+  predicate isIn() { a.getMacroName().toLowerCase().matches("%\\_in%") }
+
+  predicate isOut() { a.getMacroName().toLowerCase().matches("%\\_out%") }
+
+  predicate isInOut() { a.getMacroName().toLowerCase().matches("%\\_inout%") }
+}
+
+/**
+ * A SAL element, i.e. a SAL annotation or a declaration entry
+ * that may have SAL annotations.
+ */
+library class SALElement extends Element {
+  SALElement() {
+    containsSALAnnotation(this.(DeclarationEntry).getFile()) or
+    this instanceof SALAnnotation
+  }
+
+  predicate hasStartPosition(File file, int line, int col) {
+    exists(Location loc | loc = this.getLocation() |
+      file = loc.getFile() and
+      line = loc.getStartLine() and
+      col = loc.getStartColumn()
+    )
+  }
+
+  predicate hasEndPosition(File file, int line, int col) {
+    exists(Location loc |
+      loc = this.(FunctionDeclarationEntry).getBlock().getLocation()
+      or
+      this = any(VariableDeclarationEntry vde |
+          vde.isDefinition() and
+          loc = vde.getVariable().getInitializer().getLocation()
+        )
+    |
+      file = loc.getFile() and
+      line = loc.getEndLine() and
+      col = loc.getEndColumn()
+    )
+  }
+
+  SALPosition getStartPosition() {
+    exists(File file, int line, int col |
+      this.hasStartPosition(file, line, col) and
+      result = MkSALPosition(file, line, col)
+    )
+  }
+}
+
+/** Holds if `file` contains a SAL annotation. */
+pragma[noinline]
+private predicate containsSALAnnotation(File file) { any(SALAnnotation a).getFile() = file }
+
+/**
+ * A source-file position of a `SALElement`. Unlike location, this denotes a
+ * point in the file rather than a range.
+ */
+private newtype SALPosition =
+  MkSALPosition(File file, int line, int col) {
+    exists(SALElement e |
+      e.hasStartPosition(file, line, col)
+      or
+      e.hasEndPosition(file, line, col)
+    )
+  }
+
+/** Holds if `pos` is the start position of a SAL annotation. */
+pragma[noinline]
+private predicate salAnnotationPos(SALPosition pos) {
+  any(SALAnnotation a).(SALElement).getStartPosition() = pos
+}
+
+/**
+ * Gets the `idx`th position in `file` that holds a SAL element,
+ * ordering positions lexicographically by their start line and start column.
+ */
+private SALPosition salRelevantPositionAt(File file, int idx) {
+  result = rank[idx](SALPosition pos, int line, int col |
+      pos = MkSALPosition(file, line, col)
+    |
+      pos order by line, col
+    )
 }

cpp/ql/src/Microsoft/SAL/IgnoreReturnValueSAL.ql

@@ -0,0 +1,25 @@
+/**
+ * @name SAL requires inspecting return value
+ * @description When a return value is discarded even though the SAL annotation
+ *              requires inspecting it, a recoverable error may turn into a
+ *              whole-program crash.
+ * @kind problem
+ * @problem.severity warning
+ * @tags reliability
+ *       external/cwe/cwe-573
+ *       external/cwe/cwe-252
+ * @opaque-id SM02344
+ * @microsoft.severity Important
+ * @id cpp/ignorereturnvaluesal
+ */
+
+import Microsoft.SAL
+
+from Function f, FunctionCall call
+where
+  call.getTarget() = f and
+  call instanceof ExprInVoidContext and
+  any(SALCheckReturn a).getDeclaration() = f and
+  not any(Options o).okToIgnoreReturnValue(call)
+select call, "Return value of $@ discarded although a SAL annotation " + "requires inspecting it.",
+  f, f.getName()

cpp/ql/src/Security/CWE/CWE-190/ComparisonWithWiderType.ql

@@ -5,7 +5,7 @@
  * @id cpp/comparison-with-wider-type
  * @kind problem
  * @problem.severity warning
- * @precision medium
+ * @precision high
  * @tags reliability
  *       security
  *       external/cwe/cwe-190

cpp/ql/src/Security/CWE/CWE-457/ConditionallyUninitializedVariable.qhelp

@@ -0,0 +1,59 @@
+<!DOCTYPE qhelp PUBLIC
+  "-//Semmle//qhelp//EN"
+  "qhelp.dtd">
+<qhelp>
+
+<overview>
+<p>A common pattern is to initialize a local variable by calling another function (an
+"initialization" function) with the address of the local variable as a pointer argument. That
+function is then responsible for writing to the memory location referenced by the pointer.</p>
+
+<p>In some cases, the called function may not always write to the memory pointed to by the
+pointer argument. In such cases, the function will typically return a "status" code, informing the
+caller as to whether the initialization succeeded or not. If the caller does not check the status
+code before reading the local variable, it may read unitialized memory, which can result in
+unexpected behavior.</p>
+
+</overview>
+<recommendation>
+
+<p>When using a initialization function that does not guarantee to initialize the memory pointed to
+by the passed pointer, and returns a status code to indicate whether such initialization occurred,
+the status code should be checked before reading from the local variable.</p>
+
+</recommendation>
+<example>
+
+<p>In this hypothetical example we have code for managing a series of devices. The code
+includes a <code>DeviceConfig</code> struct that can represent properties about each device.
+The <code>initDeviceConfig</code> function can be called to initialize one of these structures, by
+providing a "device number", which can be used to look up the appropriate properties in some data
+store. If an invalid device number is provided, the function returns a status code of
+<code>-1</code>, and does not initialize the provided pointer.</p>
+
+<p>In the first code sample below, the <code>notify</code> function calls the
+<code>initDeviceConfig</code> function with a pointer to the local variable <code>config</code>,
+which is then subsequently accessed to fetch properties of the device. However, the code does not
+check the return value from the function call to <code>initDeviceConfig</code>. If the
+device number passed to the <code>notify</code> function was invalid, the
+<code>initDeviceConfig</code> function will leave the <code>config</code> variable uninitialized,
+which will result in the <code>notify</code> function accessing uninitialized memory.</p>
+
+<sample src="ConditionallyUninitializedVariableBad.c" />
+
+<p>To fix this, the code needs to check that the return value of the call to
+<code>initDeviceConfig</code> is zero. If that is true, then the calling code can safely assume
+that the local variable has been initialized.</p>
+
+<sample src="ConditionallyUninitializedVariableGood.c" />
+
+</example>
+<references>
+
+<li>
+  Wikipedia:
+  <a href="https://en.wikipedia.org/wiki/Uninitialized_variable">Uninitialized variable</a>.
+</li>
+
+</references>
+</qhelp>

cpp/ql/src/Security/CWE/CWE-457/ConditionallyUninitializedVariable.ql

@@ -0,0 +1,33 @@
+/**
+ * @name Conditionally uninitialized variable
+ * @description When an initialization function is used to initialize a local variable, but the
+ *              returned status code is not checked, the variable may be left in an uninitialized
+ *              state, and reading the variable may result in undefined behavior.
+ * @kind problem
+ * @problem.severity warning
+ * @opaque-id SM02313
+ * @id cpp/conditionally-uninitialized-variable
+ * @tags security
+ *       external/cwe/cwe-457
+ */
+
+import cpp
+import semmle.code.cpp.controlflow.SSA
+private import UninitializedVariables
+
+from
+  ConditionallyInitializedVariable v, ConditionalInitializationFunction f,
+  ConditionalInitializationCall call, string defined, Evidence e
+where
+  exists(v.getARiskyAccess(f, call, e)) and
+  (
+    if e = DefinitionInSnapshot()
+    then defined = ""
+    else
+      if e = SuggestiveSALAnnotation()
+      then defined = "externally defined (SAL) "
+      else defined = "externally defined (CSV) "
+  )
+select call,
+  "The status of this call to " + defined +
+    "$@ is not checked, potentially leaving $@ uninitialized.", f, f.getName(), v, v.getName()

cpp/ql/src/Security/CWE/CWE-457/ConditionallyUninitializedVariableBad.c

@@ -0,0 +1,25 @@
+struct DeviceConfig {
+  bool isEnabled;
+  int channel;
+};
+
+int initDeviceConfig(DeviceConfig *ref, int deviceNumber) {
+  if (deviceNumber >= getMaxDevices()) {
+    // No device with that number, return -1 to indicate failure
+    return -1;
+  }
+  // Device with that number, fetch parameters and initialize struct
+  ref->isEnabled = fetchIsDeviceEnabled(deviceNumber);
+  ref->channel = fetchDeviceChannel(deviceNumber);
+  // Return 0 to indicate success
+  return 0;
+}
+
+int notify(int deviceNumber) {
+  DeviceConfig config;
+  initDeviceConfig(&config, deviceNumber);
+  // BAD: Using config without checking the status code that is returned
+  if (config.isEnabled) {
+    notifyChannel(config.channel);
+  }
+}

cpp/ql/src/Security/CWE/CWE-457/ConditionallyUninitializedVariableGood.c

@@ -0,0 +1,27 @@
+struct DeviceConfig {
+  bool isEnabled;
+  int channel;
+};
+
+int initDeviceConfig(DeviceConfig *ref, int deviceNumber) {
+  if (deviceNumber >= getMaxDevices()) {
+    // No device with that number, return -1 to indicate failure
+    return -1;
+  }
+  // Device with that number, fetch parameters and initialize struct
+  ref->isEnabled = fetchIsDeviceEnabled(deviceNumber);
+  ref->channel = fetchDeviceChannel(deviceNumber);
+  // Return 0 to indicate success
+  return 0;
+}
+
+void notify(int deviceNumber) {
+  DeviceConfig config;
+  int statusCode = initDeviceConfig(&config, deviceNumber);
+  if (statusCode == 0) {
+    // GOOD: Status code returned by initialization function is checked, so this is safe
+    if (config.isEnabled) {
+      notifyChannel(config.channel);
+    }
+  }
+}

cpp/ql/src/Security/CWE/CWE-457/InitializationFunctions.qll

@@ -0,0 +1,705 @@
+/**
+ * Provides classes and predicates for identifying functions that initialize their arguments.
+ */
+
+import cpp
+import external.ExternalArtifact
+private import semmle.code.cpp.dispatch.VirtualDispatch
+import semmle.code.cpp.NestedFields
+import Microsoft.SAL
+import semmle.code.cpp.controlflow.Guards
+
+/** A context under which a function may be called. */
+private newtype TContext =
+  /** No specific call context. */
+  NoContext() or
+  /**
+   * The call context is that the given other parameter is null.
+   *
+   * This context is created for all parameters that are null checked in the body of the function.
+   */
+  ParamNull(Parameter p) { p = any(ParameterNullCheck pnc).getParameter() } or
+  /**
+   * The call context is that the given other parameter is not null.
+   *
+   * This context is created for all parameters that are null checked in the body of the function.
+   */
+  ParamNotNull(Parameter p) { p = any(ParameterNullCheck pnc).getParameter() }
+
+/**
+ * A context under which a function may be called.
+ *
+ * Some functions may conditionally initialize a parameter depending on the value of another
+ * parameter. Consider:
+ * ```
+ * int MyInitFunction(int* paramToBeInitialized, int* paramToCheck) {
+ *   if (!paramToCheck) {
+ *     // fail!
+ *     return -1;
+ *   }
+ *   paramToBeInitialized = 0;
+ * }
+ * ```
+ * In this case, whether `paramToBeInitialized` is initialized when this function call completes
+ * depends on whether `paramToCheck` is or is not null. A call-context insensitive analysis will
+ * determine that any call to this function may leave the parameter uninitialized, even if the
+ * argument to paramToCheck is guaranteed to be non-null (`&foo`, for example).
+ *
+ * This class models call contexts that can be considered when calculating whether a given parameter
+ * initializes or not. The supported contexts are:
+ *  - `ParamNull(otherParam)` - the given `otherParam` is considered to be null. Applies when
+ *                            exactly one parameter other than this one is null checked.
+ *  - `ParamNotNull(otherParam)` - the given `otherParam` is considered to be not null. Applies when
+ *                               exactly one parameter other than this one is null checked.
+ *  - `NoContext()` - applies in all other circumstances.
+ */
+class Context extends TContext {
+  string toString() {
+    this = NoContext() and result = "NoContext"
+    or
+    this = ParamNull(any(Parameter p | result = "ParamNull(" + p.getName() + ")"))
+    or
+    this = ParamNotNull(any(Parameter p | result = "ParamNotNull(" + p.getName() + ")"))
+  }
+}
+
+/**
+ * A check against a parameter.
+ */
+abstract class ParameterCheck extends Expr {
+  /**
+   * Gets a successor of this check that should be ignored for the given context.
+   */
+  abstract ControlFlowNode getIgnoredSuccessorForContext(Context c);
+}
+
+/** A null-check expression on a parameter. */
+class ParameterNullCheck extends ParameterCheck {
+  Parameter p;
+  ControlFlowNode nullSuccessor;
+  ControlFlowNode notNullSuccessor;
+
+  ParameterNullCheck() {
+    this.isCondition() and
+    p.getFunction() instanceof InitializationFunction and
+    p.getType().getUnspecifiedType() instanceof PointerType and
+    exists(VariableAccess va | va = p.getAnAccess() |
+      nullSuccessor = getATrueSuccessor() and
+      notNullSuccessor = getAFalseSuccessor() and
+      (
+        va = this.(NotExpr).getOperand() or
+        va = any(EQExpr eq | eq = this and eq.getAnOperand().getValue() = "0").getAnOperand() or
+        va = getAssertedFalseCondition(this) or
+        va = any(NEExpr eq |
+            eq = getAssertedFalseCondition(this) and eq.getAnOperand().getValue() = "0"
+          ).getAnOperand()
+      )
+      or
+      nullSuccessor = getAFalseSuccessor() and
+      notNullSuccessor = getATrueSuccessor() and
+      (
+        va = this or
+        va = any(NEExpr eq | eq = this and eq.getAnOperand().getValue() = "0").getAnOperand() or
+        va = any(EQExpr eq |
+            eq = getAssertedFalseCondition(this) and eq.getAnOperand().getValue() = "0"
+          ).getAnOperand()
+      )
+    )
+  }
+
+  /** The parameter being null-checked. */
+  Parameter getParameter() { result = p }
+
+  override ControlFlowNode getIgnoredSuccessorForContext(Context c) {
+    c = ParamNull(p) and result = notNullSuccessor
+    or
+    c = ParamNotNull(p) and result = nullSuccessor
+  }
+
+  /** The successor at which the parameter is confirmed to be null. */
+  ControlFlowNode getNullSuccessor() { result = nullSuccessor }
+
+  /** The successor at which the parameter is confirmed to be not-null. */
+  ControlFlowNode getNotNullSuccessor() { result = notNullSuccessor }
+}
+
+/**
+ * An entry in a CSV file in cond-init that contains externally defined functions that are
+ * conditional initializers. These files are typically produced by running the
+ * ConditionallyInitializedFunction companion query.
+ */
+class ValidatedExternalCondInitFunction extends ExternalData {
+  ValidatedExternalCondInitFunction() { this.getDataPath().matches("%cond-init%.csv") }
+
+  predicate isExternallyVerified(Function f, int param) {
+    functionSignature(f, getField(1), getField(2)) and param = getFieldAsInt(3)
+  }
+}
+
+/**
+ * The type of evidence used to determine whether a function initializes a parameter.
+ */
+newtype Evidence =
+  /**
+   * The function is defined in the snapshot, and the CFG has been analyzed to determine that the
+   * parameter is not initialized on at least one path to the exit.
+   */
+  DefinitionInSnapshot() or
+  /**
+   * The function is externally defined, but the parameter has an `_out` SAL annotation which
+   * suggests that it is initialized in the function.
+   */
+  SuggestiveSALAnnotation() or
+  /**
+   * We have been given a CSV file which indicates this parameter is conditionally initialized.
+   */
+  ExternalEvidence()
+
+/**
+ * A call to an function which initializes one or more of its parameters.
+ */
+class InitializationFunctionCall extends FunctionCall {
+  Expr initializedArgument;
+
+  InitializationFunctionCall() { initializedArgument = getAnInitializedArgument(this) }
+
+  /** Gets a parameter that is initialized by this call. */
+  Parameter getAnInitParameter() { result.getAnAccess() = initializedArgument }
+}
+
+/**
+ * A variable access which is dereferenced then assigned to.
+ */
+private predicate isPointerDereferenceAssignmentTarget(VariableAccess target) {
+  target.getParent().(PointerDereferenceExpr) = any(Assignment e).getLValue()
+}
+
+/**
+ * A function which initializes one or more of its parameters.
+ */
+class InitializationFunction extends Function {
+  int i;
+  Evidence evidence;
+
+  InitializationFunction() {
+    evidence = DefinitionInSnapshot() and
+    (
+      // Assignment by pointer dereferencing the parameter
+      isPointerDereferenceAssignmentTarget(this.getParameter(i).getAnAccess()) or
+      // Field wise assignment to the parameter
+      any(Assignment e).getLValue() = getAFieldAccess(this.getParameter(i)) or
+      i = this
+            .(MemberFunction)
+            .getAnOverridingFunction+()
+            .(InitializationFunction)
+            .initializedParameter() or
+      getParameter(i) = any(InitializationFunctionCall c).getAnInitParameter()
+    )
+    or
+    // If we have no definition, we look at SAL annotations
+    not this.isDefined() and
+    this.getParameter(i).(SALParameter).isOut() and
+    evidence = SuggestiveSALAnnotation()
+    or
+    // We have some external information that this function conditionally initializes
+    not this.isDefined() and
+    any(ValidatedExternalCondInitFunction vc).isExternallyVerified(this, i) and
+    evidence = ExternalEvidence()
+  }
+
+  /** Gets a parameter index which is initialized by this function. */
+  int initializedParameter() { result = i }
+
+  /** Gets a `ControlFlowNode` which assigns a new value to the parameter with the given index. */
+  ControlFlowNode paramReassignment(int index) {
+    index = i and
+    (
+      result = this.getParameter(i).getAnAccess() and
+      (
+        result = any(Assignment a).getLValue().(PointerDereferenceExpr).getOperand()
+        or
+        // Field wise assignment to the parameter
+        result = any(Assignment a).getLValue().(FieldAccess).getQualifier()
+        or
+        // Assignment to a nested field of the parameter
+        result = any(Assignment a).getLValue().(NestedFieldAccess).getUltimateQualifier()
+        or
+        result = getAnInitializedArgument(any(Call c))
+        or
+        exists(IfStmt check | result = check.getCondition().getAChild*() |
+          paramReassignmentCondition(check)
+        )
+      )
+      or
+      result = any(AssumeExpr e |
+          e.getEnclosingFunction() = this and e.getAChild().(Literal).getValue() = "0"
+        )
+    )
+  }
+
+  /**
+   * Helper predicate: holds if the `if` statement `check` contains a
+   * reassignment to the `i`th parameter within its `then` statement.
+   */
+  pragma[noinline]
+  private predicate paramReassignmentCondition(IfStmt check) {
+    this.paramReassignment(i).getEnclosingStmt().getParentStmt*() = check.getThen()
+  }
+
+  /** Holds if `n` can be reached without the parameter at `index` being reassigned. */
+  predicate paramNotReassignedAt(ControlFlowNode n, int index, Context c) {
+    c = getAContext(index) and
+    (
+      not exists(this.getEntryPoint()) and index = i and n = this
+      or
+      n = this.getEntryPoint() and index = i
+      or
+      exists(ControlFlowNode mid | paramNotReassignedAt(mid, index, c) |
+        n = mid.getASuccessor() and
+        not n = paramReassignment(index) and
+        /*
+         * Ignore successor edges where the parameter is null, because it is then confirmed to be
+         * initialized.
+         */
+
+        not exists(ParameterNullCheck nullCheck |
+          nullCheck = mid and
+          nullCheck = getANullCheck(index) and
+          n = nullCheck.getNullSuccessor()
+        ) and
+        /*
+         * Ignore successor edges which are excluded by the given context
+         */
+
+        not exists(ParameterCheck paramCheck | paramCheck = mid |
+          n = paramCheck.getIgnoredSuccessorForContext(c)
+        )
+      )
+    )
+  }
+
+  /** Gets a null-check on the parameter at `index`. */
+  private ParameterNullCheck getANullCheck(int index) {
+    getParameter(index) = result.getParameter()
+  }
+
+  /** Gets a parameter which is not at the given index. */
+  private Parameter getOtherParameter(int index) {
+    index = i and
+    result = getAParameter() and
+    not result.getIndex() = index
+  }
+
+  /**
+   * Gets a call `Context` that is applicable when considering whether parameter at the `index` can
+   * be conditionally initialized.
+   */
+  Context getAContext(int index) {
+    index = i and
+    /*
+     * If there is one and only one other parameter which is null checked in the body of the method,
+     * then we have two contexts to consider - that the other param is null, or that the other param
+     * is not null.
+     */
+
+    if
+      strictcount(Parameter p |
+        exists(Context c | c = ParamNull(p) or c = ParamNotNull(p)) and
+        p = getOtherParameter(index)
+      ) = 1
+    then
+      exists(Parameter p | p = getOtherParameter(index) |
+        result = ParamNull(p) or result = ParamNotNull(p)
+      )
+    else
+      // Otherwise, only consider NoContext.
+      result = NoContext()
+  }
+
+  /**
+   * Holds if this function should be whitelisted - that is, not considered as conditionally
+   * initializing its parameters.
+   */
+  predicate whitelisted() {
+    exists(string name | this.hasName(name) |
+      // Return value is not a success code but the output functions never fail.
+      name.matches("_Interlocked%")
+      or
+      // Functions that never fail, according to MSDN.
+      name = "QueryPerformanceCounter"
+      or
+      name = "QueryPerformanceFrequency"
+      or
+      // Functions that never fail post-Vista, according to MSDN.
+      name = "InitializeCriticalSectionAndSpinCount"
+      or
+      // `rand_s` writes 0 to a non-null argument if it fails, according to MSDN.
+      name = "rand_s"
+      or
+      // IntersectRect initializes the argument regardless of whether the input intersects
+      name = "IntersectRect"
+      or
+      name = "SetRect"
+      or
+      name = "UnionRect"
+      or
+      // These functions appears to have an incorrect CFG, which leads to false positives
+      name = "PhysicalToLogicalDPIPoint"
+      or
+      name = "LogicalToPhysicalDPIPoint"
+      or
+      // Sets NtProductType to default on error
+      name = "RtlGetNtProductType"
+      or
+      // Our CFG is not sophisticated enough to detect that the argument is always initialized
+      name = "StringCchLengthA"
+      or
+      // All paths init the argument, and always returns SUCCESS.
+      name = "RtlUnicodeToMultiByteSize"
+      or
+      // All paths init the argument, and always returns SUCCESS.
+      name = "RtlMultiByteToUnicodeSize"
+      or
+      // All paths init the argument, and always returns SUCCESS.
+      name = "RtlUnicodeToMultiByteN"
+      or
+      // Always initializes argument
+      name = "RtlGetFirstRange"
+      or
+      // Destination range is zeroed out on failure, assuming first two parameters are valid
+      name = "memcpy_s"
+      or
+      // This zeroes the memory unconditionally
+      name = "SeCreateAccessState"
+    )
+  }
+}
+
+/**
+ * A function which initializes one or more of its parameters, but not on all paths.
+ */
+class ConditionalInitializationFunction extends InitializationFunction {
+  Context c;
+
+  ConditionalInitializationFunction() {
+    c = this.getAContext(i) and
+    not this.whitelisted() and
+    exists(Type status | status = this.getType().getUnspecifiedType() |
+      status instanceof IntegralType or
+      status instanceof Enum
+    ) and
+    not this.getType().getName().toLowerCase() = "size_t" and
+    (
+      /*
+       * If there is no definition, consider this to be conditionally initializing (based on either
+       * SAL or external data).
+       */
+
+      not evidence = DefinitionInSnapshot()
+      or
+      /*
+       * If this function is defined in this snapshot, then it conditionally initializes if there
+       * is at least one path through the function which doesn't initialize the parameter.
+       *
+       * Explicitly ignore pure virtual functions.
+       */
+
+      this.isDefined() and
+      this.paramNotReassignedAt(this, i, c) and
+      not this instanceof PureVirtualFunction
+    )
+  }
+
+  /** Gets the evidence associated with the given parameter. */
+  Evidence getEvidence(int param) {
+    /*
+     * Note: due to the way the predicate dispatch interacts with fields, this needs to be
+     * implemented on this class, not `InitializationFunction`. If implemented on the latter it
+     * can return evidence that does not result in conditional initialization.
+     */
+
+    param = i and evidence = result
+  }
+
+  /** Gets the index of a parameter which is conditionally initialized. */
+  int conditionallyInitializedParameter(Context context) { result = i and context = c }
+}
+
+/**
+ * More elaborate tracking, flagging cases where the status is checked after
+ * the potentially uninitialized variable has been used, and ignoring cases
+ * where the status is not checked but there is no use of the potentially
+ * uninitialized variable, may be obtained via `getARiskyAccess`.
+ */
+class ConditionalInitializationCall extends FunctionCall {
+  ConditionalInitializationFunction target;
+
+  ConditionalInitializationCall() { target = getTarget(this) }
+
+  /** Gets the argument passed for the given parameter to this call. */
+  Expr getArgumentForParameter(Parameter p) {
+    p = getTarget().getAParameter() and
+    result = getArgument(p.getIndex())
+  }
+
+  /**
+   * Gets an argument conditionally initialized by this call.
+   */
+  Expr getAConditionallyInitializedArgument(ConditionalInitializationFunction condTarget, Evidence e) {
+    condTarget = target and
+    exists(Context context |
+      result = getAConditionallyInitializedArgument(this, condTarget, context, e)
+    |
+      context = NoContext()
+      or
+      exists(Parameter otherP, Expr otherArg |
+        context = ParamNotNull(otherP) or
+        context = ParamNull(otherP)
+      |
+        otherArg = getArgumentForParameter(otherP) and
+        (otherArg instanceof AddressOfExpr implies context = ParamNotNull(otherP)) and
+        (otherArg.getType() instanceof ArrayType implies context = ParamNotNull(otherP)) and
+        (otherArg.getValue() = "0" implies context = ParamNull(otherP))
+      )
+    )
+  }
+
+  VariableAccess getAConditionallyInitializedVariable() {
+    not result.getTarget().getAnAssignedValue().getASuccessor+() = result and
+    // Should not be assigned field-wise prior to the call.
+    not exists(Assignment a, FieldAccess fa |
+      fa.getQualifier() = result.getTarget().getAnAccess() and
+      a.getLValue() = fa and
+      fa.getASuccessor+() = result
+    ) and
+    result = this
+          .getArgument(getTarget(this)
+                .(ConditionalInitializationFunction)
+                .conditionallyInitializedParameter(_))
+          .(AddressOfExpr)
+          .getOperand()
+  }
+
+  Variable getStatusVariable() {
+    exists(AssignExpr a | a.getLValue() = result.getAnAccess() | a.getRValue() = this)
+    or
+    result.getInitializer().getExpr() = this
+  }
+
+  Expr getSuccessCheck() {
+    exists(this.getAFalseSuccessor()) and result = this
+    or
+    result = this.getParent() and
+    (
+      result instanceof NotExpr or
+      result.(EQExpr).getAnOperand().getValue() = "0" or
+      result.(GEExpr).getLesserOperand().getValue() = "0"
+    )
+  }
+
+  Expr getFailureCheck() {
+    result = this.getParent() and
+    (
+      result instanceof NotExpr or
+      result.(NEExpr).getAnOperand().getValue() = "0" or
+      result.(LTExpr).getLesserOperand().getValue() = "0"
+    )
+  }
+
+  private predicate inCheckedContext() {
+    exists(Call parent | this = parent.getAnArgument() |
+      parent.getTarget() instanceof Operator or
+      parent.getTarget().hasName("VerifyOkCatastrophic")
+    )
+  }
+
+  ControlFlowNode uncheckedReaches(LocalVariable var) {
+    (
+      not exists(var.getInitializer()) and
+      var = this.getAConditionallyInitializedVariable().getTarget() and
+      if exists(this.getFailureCheck())
+      then result = this.getFailureCheck().getATrueSuccessor()
+      else
+        if exists(this.getSuccessCheck())
+        then result = this.getSuccessCheck().getAFalseSuccessor()
+        else (
+          result = this.getASuccessor() and not this.inCheckedContext()
+        )
+    )
+    or
+    exists(ControlFlowNode mid | mid = uncheckedReaches(var) |
+      not mid = getStatusVariable().getAnAccess() and
+      not mid = var.getAnAccess() and
+      not exists(VariableAccess write | result = write and write = var.getAnAccess() |
+        write = any(AssignExpr a).getLValue() or
+        write = any(AddressOfExpr a).getOperand()
+      ) and
+      result = mid.getASuccessor()
+    )
+  }
+
+  VariableAccess getARiskyRead(Function f) {
+    f = this.getTarget() and
+    exists(this.getFile().getRelativePath()) and
+    result = this.uncheckedReaches(result.getTarget()) and
+    not this.(GuardCondition).controls(result.getBasicBlock(), _)
+  }
+}
+
+/**
+ * Gets the position of an argument to the call which is initialized by the call.
+ */
+pragma[nomagic]
+int initializedArgument(Call call) {
+  exists(InitializationFunction target |
+    target = getTarget(call) and
+    result = target.initializedParameter()
+  )
+}
+
+/**
+ * Gets an argument which is initialized by the call.
+ */
+Expr getAnInitializedArgument(Call call) { result = call.getArgument(initializedArgument(call)) }
+
+/**
+ * Gets the position of an argument to the call to the target which is conditionally initialized by
+ * the call, under the given context and evidence.
+ */
+pragma[nomagic]
+int conditionallyInitializedArgument(
+  Call call, ConditionalInitializationFunction target, Context c, Evidence e
+) {
+  target = getTarget(call) and
+  c = target.getAContext(result) and
+  e = target.getEvidence(result) and
+  result = target.conditionallyInitializedParameter(c)
+}
+
+/**
+ * Gets an argument which is conditionally initialized by the call to the given target under the given context and evidence.
+ */
+Expr getAConditionallyInitializedArgument(
+  Call call, ConditionalInitializationFunction target, Context c, Evidence e
+) {
+  result = call.getArgument(conditionallyInitializedArgument(call, target, c, e))
+}
+
+/**
+ * Gets the type signature for the functions parameters.
+ */
+string typeSig(Function f) {
+  result = concat(int i, Type pt |
+      pt = f.getParameter(i).getType()
+    |
+      pt.getUnspecifiedType().toString(), "," order by i
+    )
+}
+
+/**
+ * Holds where qualifiedName and typeSig make up the signature for the function.
+ */
+predicate functionSignature(Function f, string qualifiedName, string typeSig) {
+  qualifiedName = f.getQualifiedName() and
+  typeSig = typeSig(f)
+}
+
+/**
+ * Gets a possible definition for the undefined function by matching the undefined function name
+ * and parameter arity with a defined function.
+ *
+ * This is useful for identifying call to target dependencies across libraries, where the libraries
+ * are never statically linked together.
+ */
+Function getAPossibleDefinition(Function undefinedFunction) {
+  not undefinedFunction.isDefined() and
+  exists(string qn, string typeSig |
+    functionSignature(undefinedFunction, qn, typeSig) and functionSignature(result, qn, typeSig)
+  ) and
+  result.isDefined()
+}
+
+/**
+ * Helper predicate for `getTarget`, that computes possible targets of a `Call`.
+ *
+ * If there is at least one defined target after performing some simple virtual dispatch
+ * resolution, then the result is all the defined targets.
+ */
+private Function getTarget1(Call c) {
+  result = VirtualDispatch::getAViableTarget(c) and
+  result.isDefined()
+}
+
+/**
+ * Helper predicate for `getTarget`, that computes possible targets of a `Call`.
+ *
+ * If we can use the heuristic matching of functions to find definitions for some of the viable
+ * targets, return those.
+ */
+private Function getTarget2(Call c) {
+  not exists(getTarget1(c)) and
+  result = getAPossibleDefinition(VirtualDispatch::getAViableTarget(c))
+}
+
+/**
+ * Helper predicate for `getTarget`, that computes possible targets of a `Call`.
+ *
+ * Otherwise, the result is the undefined `Function` instances.
+ */
+private Function getTarget3(Call c) {
+  not exists(getTarget1(c)) and
+  not exists(getTarget2(c)) and
+  result = VirtualDispatch::getAViableTarget(c)
+}
+
+/**
+ * Gets a possible target for the `Call`, using the name and parameter matching if we did not associate
+ * this call with a specific definition at link or compile time, and performing simple virtual
+ * dispatch resolution.
+ */
+Function getTarget(Call c) {
+  result = getTarget1(c) or
+  result = getTarget2(c) or
+  result = getTarget3(c)
+}
+
+/**
+ * Get an access of a field on `Variable` v.
+ */
+FieldAccess getAFieldAccess(Variable v) {
+  exists(VariableAccess va, Expr qualifierExpr |
+    // Find an access of the variable, or an AddressOfExpr that has the access
+    va = v.getAnAccess() and
+    (
+      qualifierExpr = va or
+      qualifierExpr.(AddressOfExpr).getOperand() = va
+    )
+  |
+    // Direct field access
+    qualifierExpr = result.getQualifier()
+    or
+    // Nested field access
+    qualifierExpr = result.(NestedFieldAccess).getUltimateQualifier()
+  )
+}
+
+/**
+ * Gets a condition which is asserted to be false by the given `ne` expression, according to this pattern:
+ * ```
+ * int a = !!result;
+ * if (!a) {  // <- ne
+ *   ....
+ * }
+ * ```
+ */
+Expr getAssertedFalseCondition(NotExpr ne) {
+  exists(LocalVariable v |
+    result = v.getInitializer().getExpr().(NotExpr).getOperand().(NotExpr).getOperand() and
+    ne.getOperand() = v.getAnAccess() and
+    nonAssignedVariable(v)
+    // and not passed by val?
+  )
+}
+
+pragma[noinline]
+private predicate nonAssignedVariable(Variable v) { not exists(v.getAnAssignment()) }

cpp/ql/src/Security/CWE/CWE-457/UninitializedVariables.qll

@@ -0,0 +1,190 @@
+/**
+ * A module for identifying conditionally initialized variables.
+ */
+
+import cpp
+import InitializationFunctions
+
+// Optimised reachability predicates
+private predicate reaches(ControlFlowNode a, ControlFlowNode b) = fastTC(successor/2)(a, b)
+
+private predicate successor(ControlFlowNode a, ControlFlowNode b) { b = a.getASuccessor() }
+
+class WhitelistedCallsConfig extends string {
+  WhitelistedCallsConfig() { this = "config" }
+
+  abstract predicate isWhitelisted(Call c);
+}
+
+abstract class WhitelistedCall extends Call {
+  override Function getTarget() { none() }
+}
+
+private predicate hasConditionalInitialization(
+  ConditionalInitializationFunction f, ConditionalInitializationCall call, LocalVariable v,
+  VariableAccess initAccess, Evidence e
+) {
+  // Ignore whitelisted calls
+  not call instanceof WhitelistedCall and
+  f = getTarget(call) and
+  initAccess = v.getAnAccess() and
+  initAccess = call.getAConditionallyInitializedArgument(f, e).(AddressOfExpr).getOperand()
+}
+
+/**
+ * A variable that can be conditionally initialized by a call.
+ */
+class ConditionallyInitializedVariable extends LocalVariable {
+  ConditionalInitializationCall call;
+  ConditionalInitializationFunction f;
+  VariableAccess initAccess;
+  Evidence e;
+
+  ConditionallyInitializedVariable() {
+    // Find a call that conditionally initializes this variable
+    hasConditionalInitialization(f, call, this, initAccess, e) and
+    // Ignore cases where the variable is assigned prior to the call
+    not reaches(getAnAssignedValue(), initAccess) and
+    // Ignore cases where the variable is assigned field-wise prior to the call.
+    not exists(FieldAccess fa |
+      exists(Assignment a |
+        fa = getAFieldAccess(this) and
+        a.getLValue() = fa
+      )
+    |
+      reaches(fa, initAccess)
+    ) and
+    // Ignore cases where the variable is assigned by a prior call to an initialization function
+    not exists(Call c |
+      getAnAccess() = getAnInitializedArgument(c).(AddressOfExpr).getOperand() and
+      reaches(c, initAccess)
+    ) and
+    /*
+     * Static local variables with constant initializers do not have the initializer expr as part of
+     * the CFG, but should always be considered as initialized, so exclude them.
+     */
+
+    not exists(getInitializer().getExpr())
+  }
+
+  /**
+   * Gets an access of the variable `v` which is not used as an lvalue, and not used as an argument
+   * to an initialization function.
+   */
+  private VariableAccess getAReadAccess() {
+    result = this.getAnAccess() and
+    // Not used as an lvalue
+    not result = any(AssignExpr a).getLValue() and
+    // Not passed to another initialization function
+    not exists(Call c, int j | j = c.getTarget().(InitializationFunction).initializedParameter() |
+      result = c.getArgument(j).(AddressOfExpr).getOperand()
+    ) and
+    // Not a pointless read
+    not result = any(ExprStmt es).getExpr()
+  }
+
+  /**
+   * Gets a read access of variable `v` that occurs after the `initializingCall`.
+   */
+  private VariableAccess getAReadAccessAfterCall(ConditionalInitializationCall initializingCall) {
+    // Variable associated with this particular call
+    call = initializingCall and
+    // Access is a meaningful read access
+    result = getAReadAccess() and
+    // Which occurs after the call
+    reaches(call, result) and
+    /*
+     * Ignore risky accesses which are arguments to calls which also include another parameter to
+     * the original call. This is an attempt to eliminate results where the "status" can be checked
+     * through another parameter that assigned as part of the original call.
+     */
+
+    not exists(Call c |
+      c.getAnArgument() = result or
+      c.getAnArgument().(AddressOfExpr).getOperand() = result
+    |
+      exists(LocalVariable lv |
+        call.getAnArgument().(AddressOfExpr).getOperand() = lv.getAnAccess() and
+        not lv = this
+      |
+        c.getAnArgument() = lv.getAnAccess()
+      )
+    )
+  }
+
+  /**
+   * Gets an access to the variable that is risky because the variable may not be initialized after
+   * the `call`, and the status of the call is never checked.
+   */
+  VariableAccess getARiskyAccessWithNoStatusCheck(
+    ConditionalInitializationFunction initializingFunction,
+    ConditionalInitializationCall initializingCall, Evidence evidence
+  ) {
+    // Variable associated with this particular call
+    call = initializingCall and
+    initializingFunction = f and
+    e = evidence and
+    result = getAReadAccessAfterCall(initializingCall) and
+    (
+      // Access is risky because status return code ignored completely
+      call instanceof ExprInVoidContext
+      or
+      // Access is risky because status return code ignored completely
+      exists(LocalVariable status | call = status.getAnAssignedValue() |
+        not exists(status.getAnAccess())
+      )
+    )
+  }
+
+  /**
+   * Gets an access to the variable that is risky because the variable may not be initialized after
+   * the `call`, and the status of the call is only checked after the risky access.
+   */
+  VariableAccess getARiskyAccessBeforeStatusCheck(
+    ConditionalInitializationFunction initializingFunction,
+    ConditionalInitializationCall initializingCall, Evidence evidence
+  ) {
+    // Variable associated with this particular call
+    call = initializingCall and
+    initializingFunction = f and
+    e = evidence and
+    result = getAReadAccessAfterCall(initializingCall) and
+    exists(LocalVariable status, Assignment a |
+      a.getRValue() = call and
+      call = status.getAnAssignedValue() and
+      // There exists a check of the status code
+      definitionUsePair(status, a, _) and
+      // And the check of the status code does not occur before the risky access
+      not exists(VariableAccess statusAccess |
+        definitionUsePair(status, a, statusAccess) and
+        reaches(statusAccess, result)
+      ) and
+      // Ignore cases where the assignment to the status code is used directly
+      a instanceof ExprInVoidContext and
+      /*
+       * Ignore risky accesses which are arguments to calls which also include the status code.
+       * If both the risky value and status code are passed to a different function, that
+       * function is responsible for checking the status code.
+       */
+
+      not exists(Call c |
+        c.getAnArgument() = result or
+        c.getAnArgument().(AddressOfExpr).getOperand() = result
+      |
+        definitionUsePair(status, a, c.getAnArgument())
+      )
+    )
+  }
+
+  /**
+   * Gets an access to the variable that is risky because the variable may not be initialized after
+   * the `call`.
+   */
+  VariableAccess getARiskyAccess(
+    ConditionalInitializationFunction initializingFunction,
+    ConditionalInitializationCall initializingCall, Evidence evidence
+  ) {
+    result = getARiskyAccessBeforeStatusCheck(initializingFunction, initializingCall, evidence) or
+    result = getARiskyAccessWithNoStatusCheck(initializingFunction, initializingCall, evidence)
+  }
+}

cpp/ql/src/codeql-suites/cpp-lgtm-full.qls

@@ -0,0 +1,14 @@
+- description: Standard LGTM queries for C/C++, including ones not displayed by default
+- qlpack: codeql-cpp
+- apply: lgtm-selectors.yml
+  from: codeql-suite-helpers
+# These queries are infeasible to compute on large projects:
+- exclude:
+    query path:
+      - Security/CWE/CWE-497/ExposedSystemData.ql
+      - Critical/DescriptorMayNotBeClosed.ql
+      - Critical/DescriptorNeverClosed.ql
+      - Critical/FileMayNotBeClosed.ql
+      - Critical/FileNeverClosed.ql
+      - Critical/MemoryMayNotBeFreed.ql
+      - Critical/MemoryNeverFreed.ql

cpp/ql/src/codeql-suites/cpp-lgtm.qls

@@ -0,0 +1,4 @@
+- description: Standard LGTM queries for C/C++
+- apply: codeql-suites/cpp-lgtm-full.qls
+- apply: lgtm-displayed-only.yml
+  from: codeql-suite-helpers

cpp/ql/src/jsf/4.10 Classes/AV Rule 81.ql

@@ -51,7 +51,7 @@ class ReferenceCopyAssignmentOperator extends MemberFunction {
 
   /**
    * A call to a function called swap. Note: could be a member,
-   * std::swap or a function overloading std::swap (not in std::)
+   * `std::swap` or a function overloading `std::swap` (not in `std::`)
    * so keep it simple
    */
   FunctionCall getASwapCall() {

cpp/ql/src/jsf/4.21 Operators/AV Rule 159.ql

@@ -10,7 +10,7 @@
 
 /*
  * See More Effective C++ item 7.
- * Note: Meyers allows unary & to be overloaded but not comma
+ * Note: Meyers allows unary `&` to be overloaded but not comma.
  */
 
 import cpp

cpp/ql/src/jsf/4.28 Portable Code/AV Rule 213.ql

@@ -15,11 +15,11 @@ import cpp
 /*
  * Interpretation and deviations:
  *   - if the higher operator has precedence > arithmetic then it is fine
- *     RATIONALE: exprs like f(), *x, &x are easily understood to bind tightly
+ *     RATIONALE: exprs like `f()`, `*x`, `&x` are easily understood to bind tightly
  *   - if the higher operator is the RHS of an assign then it is fine
  *     RATIONALE: cf. MISRA, too many cases excluded otherwise
  *   - comparison operators can be mixed with arithmetic
- *     RATIONALE: x==y+z is common and unambiguous
+ *     RATIONALE: `x==y+z` is common and unambiguous
  */
 
 predicate arithmeticPrecedence(int p) { p = 12 or p = 13 }

cpp/ql/src/qlpack.yml

@@ -0,0 +1,4 @@
+name: codeql-cpp
+version: 0.0.0
+dbscheme: semmlecode.cpp.dbscheme
+suites: codeql-suites

cpp/ql/src/semmle/code/cpp/Class.qll

@@ -605,15 +605,6 @@ class Class extends UserType {
     class_instantiation(underlyingElement(this), unresolveElement(c))
   }
 
-  /**
-   * Gets the `i`th template argument used to instantiate this class from a
-   * class template. When called on a class template, this will return the
-   * `i`th template parameter.
-   */
-  override Type getTemplateArgument(int i) {
-    class_template_argument(underlyingElement(this), i, unresolveElement(result))
-  }
-
   /**
    * Holds if this class/struct is polymorphic (has a virtual function, or
    * inherits one).
@@ -623,7 +614,7 @@ class Class extends UserType {
   }
 
   override predicate involvesTemplateParameter() {
-    getATemplateArgument().involvesTemplateParameter()
+    getATemplateArgument().(Type).involvesTemplateParameter()
   }
 
   /** Holds if this class, struct or union was declared 'final'. */

cpp/ql/src/semmle/code/cpp/Declaration.qll

@@ -14,8 +14,12 @@ private import semmle.code.cpp.internal.QualifiedName as Q
  * ```
  *   extern int myglobal;
  * ```
- * Each of these declarations is given its own distinct `DeclarationEntry`,
- * but they all share the same `Declaration`.
+ * and defined in one:
+ * ```
+ *   int myglobal;
+ * ```
+ * Each of these declarations (including the definition) is given its own
+ * distinct `DeclarationEntry`, but they all share the same `Declaration`.
  *
  * Some derived class of `Declaration` do not have a corresponding
  * `DeclarationEntry`, because they always have a unique source location.
@@ -196,26 +200,99 @@ abstract class Declaration extends Locatable, @declaration {
 
   /**
    * Gets a template argument used to instantiate this declaration from a template.
-   * When called on a template, this will return a template parameter.
+   * When called on a template, this will return a template parameter type for
+   * both typed and non-typed parameters.
    */
-  final Type getATemplateArgument() { result = getTemplateArgument(_) }
+  final Locatable getATemplateArgument() { result = getTemplateArgument(_) }
+
+  /**
+   * Gets a template argument used to instantiate this declaration from a template.
+   * When called on a template, this will return a non-typed template
+   * parameter value.
+   */
+  final Locatable getATemplateArgumentKind() { result = getTemplateArgumentKind(_) }
 
   /**
    * Gets the `i`th template argument used to instantiate this declaration from a
-   * template. When called on a template, this will return the `i`th template parameter.
+   * template.
+   *
+   * For example:
+   *
+   * `template<typename T, T X> class Foo;`
+   *
+   * Will have `getTemplateArgument(0)` return `T`, and
+   * `getTemplateArgument(1)` return `X`.
+   *
+   * `Foo<int, 1> bar;
+   *
+   * Will have `getTemplateArgument())` return `int`, and
+   * `getTemplateArgument(1)` return `1`.
    */
-  Type getTemplateArgument(int index) { none() }
+  final Locatable getTemplateArgument(int index) {
+    if exists(getTemplateArgumentValue(index))
+    then result = getTemplateArgumentValue(index)
+    else result = getTemplateArgumentType(index)
+  }
+
+  /**
+   * Gets the `i`th template argument value used to instantiate this declaration
+   * from a template. When called on a template, this will return the `i`th template
+   * parameter value if it exists.
+   *
+   * For example:
+   *
+   * `template<typename T, T X> class Foo;`
+   *
+   * Will have `getTemplateArgumentKind(1)` return `T`, and no result for
+   * `getTemplateArgumentKind(0)`.
+   *
+   * `Foo<int, 10> bar;
+   *
+   * Will have `getTemplateArgumentKind(1)` return `int`, and no result for
+   * `getTemplateArgumentKind(0)`.
+   */
+  final Locatable getTemplateArgumentKind(int index) {
+    if exists(getTemplateArgumentValue(index))
+    then result = getTemplateArgumentType(index)
+    else none()
+  }
 
   /** Gets the number of template arguments for this declaration. */
   final int getNumberOfTemplateArguments() {
     result = count(int i | exists(getTemplateArgument(i)))
   }
+
+  private Type getTemplateArgumentType(int index) {
+    class_template_argument(underlyingElement(this), index, unresolveElement(result))
+    or
+    function_template_argument(underlyingElement(this), index, unresolveElement(result))
+    or
+    variable_template_argument(underlyingElement(this), index, unresolveElement(result))
+  }
+
+  private Expr getTemplateArgumentValue(int index) {
+    class_template_argument_value(underlyingElement(this), index, unresolveElement(result))
+    or
+    function_template_argument_value(underlyingElement(this), index, unresolveElement(result))
+    or
+    variable_template_argument_value(underlyingElement(this), index, unresolveElement(result))
+  }
 }
 
 /**
- * A C/C++ declaration entry. See the comment above `Declaration` for an
- * explanation of the relationship between `Declaration` and
- * `DeclarationEntry`.
+ * A C/C++ declaration entry. For example the following code contains five
+ * declaration entries:
+ * ```
+ * extern int myGlobal;
+ * int myVariable;
+ * typedef char MyChar;
+ * void myFunction();
+ * void myFunction() {
+ *   // ...
+ * }
+ * ```
+ * See the comment above `Declaration` for an explanation of the relationship
+ * between `Declaration` and `DeclarationEntry`.
  */
 abstract class DeclarationEntry extends Locatable {
   /** Gets a specifier associated with this declaration entry. */
@@ -288,8 +365,19 @@ abstract class DeclarationEntry extends Locatable {
  * A declaration that can potentially have more C++ access rights than its
  * enclosing element. This comprises `Class` (they have access to their own
  * private members) along with other `UserType`s and `Function` (they can be
- * the target of `friend` declarations).
+ * the target of `friend` declarations).  For example `MyClass` and
+ * `myFunction` in the following code:
+ * ```
+ * class MyClass
+ * {
+ * public:
+ *   ...
+ * };
  *
+ * void myFunction() {
+ *   // ...
+ * }
+ * ```
  * In the C++ standard (N4140 11.2), rules for access control revolve around
  * the informal phrase "_R_ occurs in a member or friend of class C", where
  * `AccessHolder` corresponds to this _R_.
@@ -423,8 +511,19 @@ abstract class AccessHolder extends Declaration {
 /**
  * A declaration that very likely has more C++ access rights than its
  * enclosing element. This comprises `Class` (they have access to their own
- * private members) along with any target of a `friend` declaration.
+ * private members) along with any target of a `friend` declaration.  For
+ * example `MyClass` and `friendFunction` in the following code:
+ * ```
+ * class MyClass
+ * {
+ * public:
+ *   friend void friendFunction();
+ * };
  *
+ * void friendFunction() {
+ *   // ...
+ * }
+ * ```
  * Most access rights are computed for `DirectAccessHolder` instead of
  * `AccessHolder` -- that's more efficient because there are fewer
  * `DirectAccessHolder`s. If a `DirectAccessHolder` contains an `AccessHolder`,

cpp/ql/src/semmle/code/cpp/Function.qll

@@ -343,15 +343,6 @@ class Function extends Declaration, ControlFlowNode, AccessHolder, @function {
     function_instantiation(underlyingElement(this), unresolveElement(f))
   }
 
-  /**
-   * Gets the `i`th template argument used to instantiate this function from a
-   * function template. When called on a function template, this will return the
-   * `i`th template parameter.
-   */
-  override Type getTemplateArgument(int index) {
-    function_template_argument(underlyingElement(this), index, unresolveElement(result))
-  }
-
   /**
    * Holds if this function is defined in several files. This is illegal in
    * C (though possible in some C++ compilers), and likely indicates that

cpp/ql/src/semmle/code/cpp/NestedFields.qll

@@ -0,0 +1,41 @@
+import cpp
+
+/**
+ * Gets a `Field` that is nested within the given `Struct`.
+ *
+ * This identifies `Field`s which are located in the same memory
+ */
+private Field getANestedField(Struct s) {
+  result = s.getAField()
+  or
+  exists(NestedStruct ns |
+    s = ns.getDeclaringType() and
+    result = getANestedField(ns)
+  )
+}
+
+/**
+ * Unwraps a series of field accesses to determine the inner-most qualifier.
+ */
+private Expr getUltimateQualifier(FieldAccess fa) {
+  exists(Expr qualifier | qualifier = fa.getQualifier() |
+    result = getUltimateQualifier(qualifier)
+    or
+    not qualifier instanceof FieldAccess and result = qualifier
+  )
+}
+
+/**
+ * Accesses to nested fields.
+ */
+class NestedFieldAccess extends FieldAccess {
+  Expr ultimateQualifier;
+
+  NestedFieldAccess() {
+    ultimateQualifier = getUltimateQualifier(this) and
+    getTarget() = getANestedField(ultimateQualifier.getType().stripType())
+  }
+
+  /** Gets the ultimate qualifier of this nested field access. */
+  Expr getUltimateQualifier() { result = ultimateQualifier }
+}

cpp/ql/src/semmle/code/cpp/Print.qll

@@ -35,6 +35,14 @@ private string getParameterTypeString(Type parameterType) {
   else result = parameterType.(DumpType).getTypeIdentityString()
 }
 
+private string getTemplateArgumentString(Declaration d, int i) {
+  if exists(d.getTemplateArgumentKind(i))
+  then
+    result = d.getTemplateArgumentKind(i).(DumpType).getTypeIdentityString() + " " +
+        d.getTemplateArgument(i)
+  else result = d.getTemplateArgument(i).(DumpType).getTypeIdentityString()
+}
+
 /**
  * A `Declaration` extended to add methods for generating strings useful only for dumps and debugging.
  */
@@ -56,7 +64,7 @@ abstract private class DumpDeclaration extends Declaration {
           strictconcat(int i |
             exists(this.getTemplateArgument(i))
           |
-            this.getTemplateArgument(i).(DumpType).getTypeIdentityString(), ", " order by i
+            getTemplateArgumentString(this, i), ", " order by i
           ) + ">"
     else result = ""
   }

cpp/ql/src/semmle/code/cpp/PrintAST.ql

@@ -7,3 +7,15 @@
 
 import cpp
 import PrintAST
+
+/**
+ * Temporarily tweak this class or make a copy to control which functions are
+ * printed.
+ */
+class Cfg extends PrintASTConfiguration {
+  /**
+   * TWEAK THIS PREDICATE AS NEEDED.
+   * Holds if the AST for `func` should be printed.
+   */
+  override predicate shouldPrintFunction(Function func) { any() }
+}

cpp/ql/src/semmle/code/cpp/Type.qll

@@ -210,7 +210,7 @@ class Type extends Locatable, @type {
     // A function call that provides an explicit template argument that refers to T uses T.
     // We exclude calls within instantiations, since they do not appear directly in the source.
     exists(FunctionCall c |
-      c.getAnExplicitTemplateArgument().refersTo(this) and
+      c.getAnExplicitTemplateArgument().(Type).refersTo(this) and
       result = c and
       not c.getEnclosingFunction().isConstructedFrom(_)
     )
@@ -610,7 +610,9 @@ class FloatingPointType extends ArithmeticType {
       (
         kind >= 24 and kind <= 32
         or
-        kind = 38
+        kind >= 38 and kind <= 42
+        or
+        kind >= 45 and kind <= 50
       )
     )
   }

cpp/ql/src/semmle/code/cpp/Variable.qll

@@ -155,15 +155,6 @@ class Variable extends Declaration, @variable {
     variable_instantiation(underlyingElement(this), unresolveElement(v))
   }
 
-  /**
-   * Gets the `i`th template argument used to instantiate this variable from a
-   * variable template. When called on a variable template, this will return the
-   * `i`th template parameter.
-   */
-  override Type getTemplateArgument(int index) {
-    variable_template_argument(underlyingElement(this), index, unresolveElement(result))
-  }
-
   /**
    * Holds if this is a compiler-generated variable. For example, a
    * [range-based for loop](http://en.cppreference.com/w/cpp/language/range-for)

cpp/ql/src/semmle/code/cpp/commons/VoidContext.qll

@@ -35,7 +35,8 @@ private predicate exprInVoidContext(Expr e) {
     exists(CommaExpr c | c.getLeftOperand() = e)
     or
     exists(CommaExpr c | c.getRightOperand() = e and c instanceof ExprInVoidContext)
+    or
+    exists(ForStmt for | for.getUpdate() = e)
   ) and
-  not e instanceof Qualifier and
   not e.getActualType() instanceof VoidType
 }

cpp/ql/src/semmle/code/cpp/controlflow/ControlFlowGraph.qll

@@ -1,6 +1,7 @@
 import cpp
 import BasicBlocks
 private import semmle.code.cpp.controlflow.internal.ConstantExprs
+private import semmle.code.cpp.controlflow.internal.CFG
 
 /**
  * A control-flow node is either a statement or an expression; in addition,
@@ -86,11 +87,11 @@ import ControlFlowGraphPublic
 class ControlFlowNodeBase extends ElementBase, @cfgnode { }
 
 predicate truecond_base(ControlFlowNodeBase n1, ControlFlowNodeBase n2) {
-  truecond(unresolveElement(n1), unresolveElement(n2))
+  qlCFGTrueSuccessor(n1, n2)
 }
 
 predicate falsecond_base(ControlFlowNodeBase n1, ControlFlowNodeBase n2) {
-  falsecond(unresolveElement(n1), unresolveElement(n2))
+  qlCFGFalseSuccessor(n1, n2)
 }
 
 /**
@@ -120,7 +121,7 @@ abstract class AdditionalControlFlowEdge extends ControlFlowNodeBase {
  * `AdditionalControlFlowEdge`. Use this relation instead of `successors`.
  */
 predicate successors_extended(ControlFlowNodeBase source, ControlFlowNodeBase target) {
-  successors(unresolveElement(source), unresolveElement(target))
+  qlCFGSuccessor(source, target)
   or
   source.(AdditionalControlFlowEdge).getAnEdgeTarget() = target
 }

cpp/ql/src/semmle/code/cpp/controlflow/Guards.qll

@@ -156,7 +156,7 @@ private predicate compares_eq(
 
 /**
  * If `test => part` and `part => left == right + k` then `test => left == right + k`.
- *    Similarly for the case where `test` is false.
+ * Similarly for the case where `test` is false.
  */
 private predicate logical_comparison_eq(
   BinaryLogicalOperation test, Expr left, Expr right, int k, boolean areEqual, boolean testIsTrue
@@ -275,7 +275,7 @@ private predicate compares_ge(
 
 /**
  * If `test => part` and `part => left < right + k` then `test => left < right + k`.
- *    Similarly for the case where `test` evaluates false.
+ * Similarly for the case where `test` evaluates false.
  */
 private predicate logical_comparison_lt(
   BinaryLogicalOperation test, Expr left, Expr right, int k, boolean isLt, boolean testIsTrue
@@ -362,7 +362,7 @@ private predicate add_lt(
   )
 }
 
-/** The int value of integer constant expression. */
+/** The `int` value of integer constant expression. */
 private int int_value(Expr e) {
   e.getUnderlyingType() instanceof IntegralType and
   result = e.getValue().toInt()

cpp/ql/src/semmle/code/cpp/controlflow/SSA.qll

@@ -29,11 +29,11 @@ class SsaDefinition extends ControlFlowNodeBase {
 
   /**
    * Gets a string representation of the SSA variable represented by the pair
-   * (this, v).
+   * `(this, v)`.
    */
   string toString(LocalScopeVariable v) { exists(StandardSSA x | result = x.toString(this, v)) }
 
-  /** Gets a use of the SSA variable represented by the pair (this, v). */
+  /** Gets a use of the SSA variable represented by the pair `(this, v)`. */
   VariableAccess getAUse(LocalScopeVariable v) {
     exists(StandardSSA x | result = x.getAUse(this, v))
   }

cpp/ql/src/semmle/code/cpp/controlflow/internal/CFG.qll

@@ -173,49 +173,36 @@ predicate excludeNode(Node n) {
   excludeNode(n.getParentNode())
 }
 
-private newtype TPos =
-  PosBefore() or
-  PosAt() or
-  PosAfter() or
-  PosBeforeDestructors() or
-  PosAfterDestructors()
-
-/** A `Pos` without a `bindingset` requirement on the constructor. */
-private class AnyPos extends TPos {
-  string toString() { result = "Pos" }
-}
-
 /**
  * A constant that indicates the type of sub-node in a pair of `(Node, Pos)`.
  * See the comment block at the top of this file.
  */
-private class Pos extends AnyPos {
-  // This is to make sure we get compile errors in code that forgets to restrict a `Pos`.
+private class Pos extends int {
   bindingset[this]
   Pos() { any() }
 
   /** Holds if this is the position just _before_ the associated `Node`. */
-  predicate isBefore() { this = PosBefore() }
+  predicate isBefore() { this = 0 }
 
   /** Holds if `(n, this)` is the sub-node that represents `n` itself. */
-  predicate isAt() { this = PosAt() }
+  predicate isAt() { this = 1 }
 
   /** Holds if this is the position just _after_ the associated `Node`. */
-  predicate isAfter() { this = PosAfter() }
+  predicate isAfter() { this = 2 }
 
   /**
    * Holds if `(n, this)` is the virtual sub-node that comes just _before_ any
    * implicit destructor calls following `n`. The node `n` will be some node
    * that may be followed by local variables going out of scope.
    */
-  predicate isBeforeDestructors() { this = PosBeforeDestructors() }
+  predicate isBeforeDestructors() { this = 3 }
 
   /**
    * Holds if `(n, this)` is the virtual sub-node that comes just _after_ any
    * implicit destructor calls following `n`. The node `n` will be some node
    * that may be followed by local variables going out of scope.
    */
-  predicate isAfterDestructors() { this = PosAfterDestructors() }
+  predicate isAfterDestructors() { this = 4 }
 
   pragma[inline]
   predicate nodeBefore(Node n, Node nEq) { this.isBefore() and n = nEq }
@@ -489,17 +476,6 @@ private Node getLastControlOrderChild(Node n) {
   result = getControlOrderChildDense(n, max(int i | exists(getControlOrderChildDense(n, i))))
 }
 
-private newtype TSpec =
-  SpecPos(AnyPos p) or
-  SpecAround() or
-  SpecAroundDestructors() or
-  SpecBarrier()
-
-/** A `Spec` without a `bindingset` requirement on the constructor. */
-private class AnySpec extends TSpec {
-  string toString() { result = "Spec" }
-}
-
 /**
  * A constant that represents two positions: one position for when it's used as
  * the _source_ of a sub-edge, and another position for when it's used as the
@@ -507,25 +483,10 @@ private class AnySpec extends TSpec {
  * themselves as both source and target, as well as two _around_ values and a
  * _barrier_ value.
  */
-private class Spec extends AnySpec {
+private class Spec extends Pos {
   bindingset[this]
   Spec() { any() }
 
-  /** See Pos.isBefore. */
-  predicate isBefore() { this = SpecPos(PosBefore()) }
-
-  /** See Pos.isAt. */
-  predicate isAt() { this = SpecPos(PosAt()) }
-
-  /** See Pos.isAfter. */
-  predicate isAfter() { this = SpecPos(PosAfter()) }
-
-  /** See Pos.isBeforeDestructors. */
-  predicate isBeforeDestructors() { this = SpecPos(PosBeforeDestructors()) }
-
-  /** See Pos.isAfterDestructors. */
-  predicate isAfterDestructors() { this = SpecPos(PosAfterDestructors()) }
-
   /**
    * Holds if this spec, when used on a node `n` between `(n1, p1)` and
    * `(n2, p2)`, should add the following sub-edges.
@@ -533,7 +494,7 @@ private class Spec extends AnySpec {
    *     (n1, p1) ----> before(n)
    *     after(n) ----> (n2, p2)
    */
-  predicate isAround() { this = SpecAround() }
+  predicate isAround() { this = 5 }
 
   /**
    * Holds if this spec, when used on a node `n` between `(n1, p1)` and
@@ -542,16 +503,17 @@ private class Spec extends AnySpec {
    *     (n1, p1)            ----> beforeDestructors(n)
    *     afterDestructors(n) ----> (n2, p2)
    */
-  predicate isAroundDestructors() { this = SpecAroundDestructors() }
+  predicate isAroundDestructors() { this = 6 }
 
   /**
    * Holds if this node is a _barrier_. A barrier resolves to no positions and
    * can be inserted between nodes that should have no sub-edges between them.
    */
-  predicate isBarrier() { this = SpecBarrier() }
+  predicate isBarrier() { this = 7 }
 
   Pos getSourcePos() {
-    this = SpecPos(result)
+    this = [0 .. 4] and
+    result = this
     or
     this.isAround() and
     result.isAfter()
@@ -561,7 +523,8 @@ private class Spec extends AnySpec {
   }
 
   Pos getTargetPos() {
-    this = SpecPos(result)
+    this = [0 .. 4] and
+    result = this
     or
     this.isAround() and
     result.isBefore()
@@ -888,6 +851,21 @@ private predicate subEdge(Pos p1, Node n1, Node n2, Pos p2) {
     p2.nodeAfter(n2, s)
   )
   or
+  // ConstexprIfStmt -> condition ; { then, else } -> // same as IfStmt
+  exists(ConstexprIfStmt s |
+    p1.nodeAt(n1, s) and
+    p2.nodeBefore(n2, s.getCondition())
+    or
+    p1.nodeAfter(n1, s.getThen()) and
+    p2.nodeBeforeDestructors(n2, s)
+    or
+    p1.nodeAfter(n1, s.getElse()) and
+    p2.nodeBeforeDestructors(n2, s)
+    or
+    p1.nodeAfterDestructors(n1, s) and
+    p2.nodeAfter(n2, s)
+  )
+  or
   // WhileStmt -> condition ; body -> condition ; after dtors -> after
   exists(WhileStmt s |
     p1.nodeAt(n1, s) and
@@ -1175,9 +1153,8 @@ private class ExceptionSource extends Node {
 }
 
 /**
- * Holds if `test` is the test of a control-flow construct that will always
- * have true/false sub-edges out of it, where the `truth`-sub-edge goes to
- * `(n2, p2)`.
+ * Holds if `test` is the test of a control-flow construct where the `truth`
+ * sub-edge goes to `(n2, p2)`.
  */
 private predicate conditionJumpsTop(Expr test, boolean truth, Node n2, Pos p2) {
   exists(IfStmt s | test = s.getCondition() |
@@ -1192,6 +1169,24 @@ private predicate conditionJumpsTop(Expr test, boolean truth, Node n2, Pos p2) {
     p2.nodeBeforeDestructors(n2, s)
   )
   or
+  exists(ConstexprIfStmt s, string cond |
+    test = s.getCondition() and
+    cond = test.getFullyConverted().getValue()
+  |
+    truth = true and
+    cond != "0" and
+    p2.nodeBefore(n2, s.getThen())
+    or
+    truth = false and
+    cond = "0" and
+    p2.nodeBefore(n2, s.getElse())
+    or
+    not exists(s.getElse()) and
+    truth = false and
+    cond = "0" and
+    p2.nodeBeforeDestructors(n2, s)
+  )
+  or
   exists(Loop l |
     (
       l instanceof WhileStmt

cpp/ql/src/semmle/code/cpp/dataflow/internal/DataFlowImpl.qll

@@ -905,30 +905,35 @@ private predicate localFlowExit(Node node, Configuration config) {
  */
 pragma[nomagic]
 private predicate localFlowStepPlus(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext cc
 ) {
-  localFlowEntry(node1, config) and
+  not isUnreachableInCall(node2, cc.(LocalCallContextSpecificCall).getCall()) and
   (
-    localFlowStep(node1, node2, config) and preservesValue = true
+    localFlowEntry(node1, config) and
+    (
+      localFlowStep(node1, node2, config) and preservesValue = true
+      or
+      additionalLocalFlowStep(node1, node2, config) and preservesValue = false
+    ) and
+    node1 != node2 and
+    cc.relevantFor(node1.getEnclosingCallable()) and
+    not isUnreachableInCall(node1, cc.(LocalCallContextSpecificCall).getCall()) and
+    nodeCand(node2, unbind(config))
     or
-    additionalLocalFlowStep(node1, node2, config) and preservesValue = false
-  ) and
-  node1 != node2 and
-  nodeCand(node2, unbind(config))
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, preservesValue, config) and
-    localFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    nodeCand(node2, unbind(config))
-  )
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, _, config) and
-    additionalLocalFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    preservesValue = false and
-    nodeCand(node2, unbind(config))
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, preservesValue, config, cc) and
+      localFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      nodeCand(node2, unbind(config))
+    )
+    or
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, _, config, cc) and
+      additionalLocalFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      preservesValue = false and
+      nodeCand(node2, unbind(config))
+    )
   )
 }
 
@@ -936,11 +941,11 @@ private predicate localFlowStepPlus(
  * Holds if `node1` can step to `node2` in one or more local steps and this
  * path can occur as a maximal subsequence of local steps in a dataflow path.
  */
-pragma[noinline]
+pragma[nomagic]
 private predicate localFlowBigStep(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext callContext
 ) {
-  localFlowStepPlus(node1, node2, preservesValue, config) and
+  localFlowStepPlus(node1, node2, preservesValue, config, callContext) and
   localFlowExit(node2, config)
 }
 
@@ -1000,7 +1005,7 @@ private class AccessPathFrontNilNode extends Node {
     (
       any(Configuration c).isSource(this)
       or
-      localFlowBigStep(_, this, false, _)
+      localFlowBigStep(_, this, false, _, _)
       or
       additionalJumpStep(_, this, _)
     )
@@ -1023,12 +1028,12 @@ private predicate flowCandFwd0(Node node, boolean fromArg, AccessPathFront apf,
   (
     exists(Node mid |
       flowCandFwd(mid, fromArg, apf, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathFrontNil nil |
       flowCandFwd(mid, fromArg, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       apf = node.(AccessPathFrontNilNode).getApf()
     )
     or
@@ -1122,13 +1127,13 @@ private predicate flowCand0(Node node, boolean toReturn, AccessPathFront apf, Co
   apf instanceof AccessPathFrontNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flowCand(mid, toReturn, apf, config)
   )
   or
   exists(Node mid, AccessPathFrontNil nil |
     flowCandFwd(node, _, apf, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flowCand(mid, toReturn, nil, config) and
     apf instanceof AccessPathFrontNil
   )
@@ -1261,7 +1266,7 @@ abstract private class AccessPath extends TAccessPath {
 
 private class AccessPathNil extends AccessPath, TNil {
   override string toString() {
-    exists(DataFlowType t | this = TNil(t) | result = concat(" : " + ppReprType(t)))
+    exists(DataFlowType t | this = TNil(t) | result = concat(": " + ppReprType(t)))
   }
 
   override AccessPathFront getFront() {
@@ -1277,7 +1282,7 @@ private class AccessPathConsNil extends AccessPathCons, TConsNil {
   override string toString() {
     exists(Content f, DataFlowType t | this = TConsNil(f, t) |
       // The `concat` becomes "" if `ppReprType` has no result.
-      result = f.toString() + concat(" : " + ppReprType(t))
+      result = "[" + f.toString() + "]" + concat(" : " + ppReprType(t))
     )
   }
 
@@ -1294,8 +1299,8 @@ private class AccessPathConsCons extends AccessPathCons, TConsCons {
   override string toString() {
     exists(Content f1, Content f2, int len | this = TConsCons(f1, f2, len) |
       if len = 2
-      then result = f1.toString() + ", " + f2.toString()
-      else result = f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")"
+      then result = "[" + f1.toString() + ", " + f2.toString() + "]"
+      else result = "[" + f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")]"
     )
   }
 
@@ -1363,12 +1368,12 @@ private predicate flowFwd0(
   (
     exists(Node mid |
       flowFwd(mid, fromArg, apf, ap, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathNil nil |
       flowFwd(mid, fromArg, _, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       ap = node.(AccessPathNilNode).getAp() and
       apf = ap.(AccessPathNil).getFront()
     )
@@ -1472,13 +1477,13 @@ private predicate flow0(Node node, boolean toReturn, AccessPath ap, Configuratio
   ap instanceof AccessPathNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flow(mid, toReturn, ap, config)
   )
   or
   exists(Node mid, AccessPathNil nil |
     flowFwd(node, _, _, ap, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flow(mid, toReturn, nil, config) and
     ap instanceof AccessPathNil
   )
@@ -1626,7 +1631,7 @@ abstract class PathNode extends TPathNode {
     this instanceof PathNodeSink and result = ""
     or
     exists(string s | s = this.(PathNodeMid).getAp().toString() |
-      if s = "" then result = "" else result = " [" + s + "]"
+      if s = "" then result = "" else result = " " + s
     )
   }
 
@@ -1729,14 +1734,20 @@ private class PathNodeSink extends PathNode, TPathNodeSink {
  * a callable is recorded by `cc`.
  */
 private predicate pathStep(PathNodeMid mid, Node node, CallContext cc, AccessPath ap) {
-  localFlowBigStep(mid.getNode(), node, true, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  ap = mid.getAp()
-  or
-  localFlowBigStep(mid.getNode(), node, false, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  mid.getAp() instanceof AccessPathNil and
-  ap = node.(AccessPathNilNode).getAp()
+  exists(LocalCallContext localCC, AccessPath ap0, Node midnode, Configuration conf |
+    midnode = mid.getNode() and
+    conf = mid.getConfiguration() and
+    cc = mid.getCallContext() and
+    localCC = getLocalCallContext(cc, midnode.getEnclosingCallable()) and
+    ap0 = mid.getAp()
+  |
+    localFlowBigStep(midnode, node, true, conf, localCC) and
+    ap = ap0
+    or
+    localFlowBigStep(midnode, node, false, conf, localCC) and
+    ap0 instanceof AccessPathNil and
+    ap = node.(AccessPathNilNode).getAp()
+  )
   or
   jumpStep(mid.getNode(), node, mid.getConfiguration()) and
   cc instanceof CallContextAny and
@@ -1880,7 +1891,7 @@ private predicate pathIntoCallable(
     pathIntoCallable0(mid, callable, i, outercc, call, emptyAp) and
     p.isParameterOf(callable, i)
   |
-    if reducedViableImplInCallContext(_, callable, call)
+    if recordDataFlowCallSite(call, callable)
     then innercc = TSpecificCall(call, i, emptyAp)
     else innercc = TSomeCall(p, emptyAp)
   )
@@ -2071,7 +2082,7 @@ private module FlowExploration {
 
   private class PartialAccessPathNil extends PartialAccessPath, TPartialNil {
     override string toString() {
-      exists(DataFlowType t | this = TPartialNil(t) | result = concat(" : " + ppReprType(t)))
+      exists(DataFlowType t | this = TPartialNil(t) | result = concat(": " + ppReprType(t)))
     }
 
     override AccessPathFront getFront() {
@@ -2083,8 +2094,8 @@ private module FlowExploration {
     override string toString() {
       exists(Content f, int len | this = TPartialCons(f, len) |
         if len = 1
-        then result = f.toString()
-        else result = f.toString() + ", ... (" + len.toString() + ")"
+        then result = "[" + f.toString() + "]"
+        else result = "[" + f.toString() + ", ... (" + len.toString() + ")]"
       )
     }
 
@@ -2161,7 +2172,7 @@ private module FlowExploration {
 
     private string ppAp() {
       exists(string s | s = this.(PartialPathNodePriv).getAp().toString() |
-        if s = "" then result = "" else result = " [" + s + "]"
+        if s = "" then result = "" else result = " " + s
       )
     }
 
@@ -2205,16 +2216,19 @@ private module FlowExploration {
   private predicate partialPathStep(
     PartialPathNodePriv mid, Node node, CallContext cc, PartialAccessPath ap, Configuration config
   ) {
-    localFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    ap = mid.getAp() and
-    config = mid.getConfiguration()
-    or
-    additionalLocalFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    mid.getAp() instanceof PartialAccessPathNil and
-    ap = TPartialNil(getErasedRepr(node.getType())) and
-    config = mid.getConfiguration()
+    not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall()) and
+    (
+      localFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      ap = mid.getAp() and
+      config = mid.getConfiguration()
+      or
+      additionalLocalFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      mid.getAp() instanceof PartialAccessPathNil and
+      ap = TPartialNil(getErasedRepr(node.getType())) and
+      config = mid.getConfiguration()
+    )
     or
     jumpStep(mid.getNode(), node, config) and
     cc instanceof CallContextAny and
@@ -2378,7 +2392,7 @@ private module FlowExploration {
       partialPathIntoCallable0(mid, callable, i, outercc, call, emptyAp, ap, config) and
       p.isParameterOf(callable, i)
     |
-      if reducedViableImplInCallContext(_, callable, call)
+      if recordDataFlowCallSite(call, callable)
       then innercc = TSpecificCall(call, i, emptyAp)
       else innercc = TSomeCall(p, emptyAp)
     )

cpp/ql/src/semmle/code/cpp/dataflow/internal/DataFlowImpl2.qll

@@ -905,30 +905,35 @@ private predicate localFlowExit(Node node, Configuration config) {
  */
 pragma[nomagic]
 private predicate localFlowStepPlus(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext cc
 ) {
-  localFlowEntry(node1, config) and
+  not isUnreachableInCall(node2, cc.(LocalCallContextSpecificCall).getCall()) and
   (
-    localFlowStep(node1, node2, config) and preservesValue = true
+    localFlowEntry(node1, config) and
+    (
+      localFlowStep(node1, node2, config) and preservesValue = true
+      or
+      additionalLocalFlowStep(node1, node2, config) and preservesValue = false
+    ) and
+    node1 != node2 and
+    cc.relevantFor(node1.getEnclosingCallable()) and
+    not isUnreachableInCall(node1, cc.(LocalCallContextSpecificCall).getCall()) and
+    nodeCand(node2, unbind(config))
     or
-    additionalLocalFlowStep(node1, node2, config) and preservesValue = false
-  ) and
-  node1 != node2 and
-  nodeCand(node2, unbind(config))
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, preservesValue, config) and
-    localFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    nodeCand(node2, unbind(config))
-  )
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, _, config) and
-    additionalLocalFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    preservesValue = false and
-    nodeCand(node2, unbind(config))
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, preservesValue, config, cc) and
+      localFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      nodeCand(node2, unbind(config))
+    )
+    or
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, _, config, cc) and
+      additionalLocalFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      preservesValue = false and
+      nodeCand(node2, unbind(config))
+    )
   )
 }
 
@@ -936,11 +941,11 @@ private predicate localFlowStepPlus(
  * Holds if `node1` can step to `node2` in one or more local steps and this
  * path can occur as a maximal subsequence of local steps in a dataflow path.
  */
-pragma[noinline]
+pragma[nomagic]
 private predicate localFlowBigStep(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext callContext
 ) {
-  localFlowStepPlus(node1, node2, preservesValue, config) and
+  localFlowStepPlus(node1, node2, preservesValue, config, callContext) and
   localFlowExit(node2, config)
 }
 
@@ -1000,7 +1005,7 @@ private class AccessPathFrontNilNode extends Node {
     (
       any(Configuration c).isSource(this)
       or
-      localFlowBigStep(_, this, false, _)
+      localFlowBigStep(_, this, false, _, _)
       or
       additionalJumpStep(_, this, _)
     )
@@ -1023,12 +1028,12 @@ private predicate flowCandFwd0(Node node, boolean fromArg, AccessPathFront apf,
   (
     exists(Node mid |
       flowCandFwd(mid, fromArg, apf, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathFrontNil nil |
       flowCandFwd(mid, fromArg, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       apf = node.(AccessPathFrontNilNode).getApf()
     )
     or
@@ -1122,13 +1127,13 @@ private predicate flowCand0(Node node, boolean toReturn, AccessPathFront apf, Co
   apf instanceof AccessPathFrontNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flowCand(mid, toReturn, apf, config)
   )
   or
   exists(Node mid, AccessPathFrontNil nil |
     flowCandFwd(node, _, apf, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flowCand(mid, toReturn, nil, config) and
     apf instanceof AccessPathFrontNil
   )
@@ -1261,7 +1266,7 @@ abstract private class AccessPath extends TAccessPath {
 
 private class AccessPathNil extends AccessPath, TNil {
   override string toString() {
-    exists(DataFlowType t | this = TNil(t) | result = concat(" : " + ppReprType(t)))
+    exists(DataFlowType t | this = TNil(t) | result = concat(": " + ppReprType(t)))
   }
 
   override AccessPathFront getFront() {
@@ -1277,7 +1282,7 @@ private class AccessPathConsNil extends AccessPathCons, TConsNil {
   override string toString() {
     exists(Content f, DataFlowType t | this = TConsNil(f, t) |
       // The `concat` becomes "" if `ppReprType` has no result.
-      result = f.toString() + concat(" : " + ppReprType(t))
+      result = "[" + f.toString() + "]" + concat(" : " + ppReprType(t))
     )
   }
 
@@ -1294,8 +1299,8 @@ private class AccessPathConsCons extends AccessPathCons, TConsCons {
   override string toString() {
     exists(Content f1, Content f2, int len | this = TConsCons(f1, f2, len) |
       if len = 2
-      then result = f1.toString() + ", " + f2.toString()
-      else result = f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")"
+      then result = "[" + f1.toString() + ", " + f2.toString() + "]"
+      else result = "[" + f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")]"
     )
   }
 
@@ -1363,12 +1368,12 @@ private predicate flowFwd0(
   (
     exists(Node mid |
       flowFwd(mid, fromArg, apf, ap, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathNil nil |
       flowFwd(mid, fromArg, _, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       ap = node.(AccessPathNilNode).getAp() and
       apf = ap.(AccessPathNil).getFront()
     )
@@ -1472,13 +1477,13 @@ private predicate flow0(Node node, boolean toReturn, AccessPath ap, Configuratio
   ap instanceof AccessPathNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flow(mid, toReturn, ap, config)
   )
   or
   exists(Node mid, AccessPathNil nil |
     flowFwd(node, _, _, ap, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flow(mid, toReturn, nil, config) and
     ap instanceof AccessPathNil
   )
@@ -1626,7 +1631,7 @@ abstract class PathNode extends TPathNode {
     this instanceof PathNodeSink and result = ""
     or
     exists(string s | s = this.(PathNodeMid).getAp().toString() |
-      if s = "" then result = "" else result = " [" + s + "]"
+      if s = "" then result = "" else result = " " + s
     )
   }
 
@@ -1729,14 +1734,20 @@ private class PathNodeSink extends PathNode, TPathNodeSink {
  * a callable is recorded by `cc`.
  */
 private predicate pathStep(PathNodeMid mid, Node node, CallContext cc, AccessPath ap) {
-  localFlowBigStep(mid.getNode(), node, true, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  ap = mid.getAp()
-  or
-  localFlowBigStep(mid.getNode(), node, false, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  mid.getAp() instanceof AccessPathNil and
-  ap = node.(AccessPathNilNode).getAp()
+  exists(LocalCallContext localCC, AccessPath ap0, Node midnode, Configuration conf |
+    midnode = mid.getNode() and
+    conf = mid.getConfiguration() and
+    cc = mid.getCallContext() and
+    localCC = getLocalCallContext(cc, midnode.getEnclosingCallable()) and
+    ap0 = mid.getAp()
+  |
+    localFlowBigStep(midnode, node, true, conf, localCC) and
+    ap = ap0
+    or
+    localFlowBigStep(midnode, node, false, conf, localCC) and
+    ap0 instanceof AccessPathNil and
+    ap = node.(AccessPathNilNode).getAp()
+  )
   or
   jumpStep(mid.getNode(), node, mid.getConfiguration()) and
   cc instanceof CallContextAny and
@@ -1880,7 +1891,7 @@ private predicate pathIntoCallable(
     pathIntoCallable0(mid, callable, i, outercc, call, emptyAp) and
     p.isParameterOf(callable, i)
   |
-    if reducedViableImplInCallContext(_, callable, call)
+    if recordDataFlowCallSite(call, callable)
     then innercc = TSpecificCall(call, i, emptyAp)
     else innercc = TSomeCall(p, emptyAp)
   )
@@ -2071,7 +2082,7 @@ private module FlowExploration {
 
   private class PartialAccessPathNil extends PartialAccessPath, TPartialNil {
     override string toString() {
-      exists(DataFlowType t | this = TPartialNil(t) | result = concat(" : " + ppReprType(t)))
+      exists(DataFlowType t | this = TPartialNil(t) | result = concat(": " + ppReprType(t)))
     }
 
     override AccessPathFront getFront() {
@@ -2083,8 +2094,8 @@ private module FlowExploration {
     override string toString() {
       exists(Content f, int len | this = TPartialCons(f, len) |
         if len = 1
-        then result = f.toString()
-        else result = f.toString() + ", ... (" + len.toString() + ")"
+        then result = "[" + f.toString() + "]"
+        else result = "[" + f.toString() + ", ... (" + len.toString() + ")]"
       )
     }
 
@@ -2161,7 +2172,7 @@ private module FlowExploration {
 
     private string ppAp() {
       exists(string s | s = this.(PartialPathNodePriv).getAp().toString() |
-        if s = "" then result = "" else result = " [" + s + "]"
+        if s = "" then result = "" else result = " " + s
       )
     }
 
@@ -2205,16 +2216,19 @@ private module FlowExploration {
   private predicate partialPathStep(
     PartialPathNodePriv mid, Node node, CallContext cc, PartialAccessPath ap, Configuration config
   ) {
-    localFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    ap = mid.getAp() and
-    config = mid.getConfiguration()
-    or
-    additionalLocalFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    mid.getAp() instanceof PartialAccessPathNil and
-    ap = TPartialNil(getErasedRepr(node.getType())) and
-    config = mid.getConfiguration()
+    not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall()) and
+    (
+      localFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      ap = mid.getAp() and
+      config = mid.getConfiguration()
+      or
+      additionalLocalFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      mid.getAp() instanceof PartialAccessPathNil and
+      ap = TPartialNil(getErasedRepr(node.getType())) and
+      config = mid.getConfiguration()
+    )
     or
     jumpStep(mid.getNode(), node, config) and
     cc instanceof CallContextAny and
@@ -2378,7 +2392,7 @@ private module FlowExploration {
       partialPathIntoCallable0(mid, callable, i, outercc, call, emptyAp, ap, config) and
       p.isParameterOf(callable, i)
     |
-      if reducedViableImplInCallContext(_, callable, call)
+      if recordDataFlowCallSite(call, callable)
       then innercc = TSpecificCall(call, i, emptyAp)
       else innercc = TSomeCall(p, emptyAp)
     )

cpp/ql/src/semmle/code/cpp/dataflow/internal/DataFlowImpl3.qll

@@ -905,30 +905,35 @@ private predicate localFlowExit(Node node, Configuration config) {
  */
 pragma[nomagic]
 private predicate localFlowStepPlus(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext cc
 ) {
-  localFlowEntry(node1, config) and
+  not isUnreachableInCall(node2, cc.(LocalCallContextSpecificCall).getCall()) and
   (
-    localFlowStep(node1, node2, config) and preservesValue = true
+    localFlowEntry(node1, config) and
+    (
+      localFlowStep(node1, node2, config) and preservesValue = true
+      or
+      additionalLocalFlowStep(node1, node2, config) and preservesValue = false
+    ) and
+    node1 != node2 and
+    cc.relevantFor(node1.getEnclosingCallable()) and
+    not isUnreachableInCall(node1, cc.(LocalCallContextSpecificCall).getCall()) and
+    nodeCand(node2, unbind(config))
     or
-    additionalLocalFlowStep(node1, node2, config) and preservesValue = false
-  ) and
-  node1 != node2 and
-  nodeCand(node2, unbind(config))
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, preservesValue, config) and
-    localFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    nodeCand(node2, unbind(config))
-  )
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, _, config) and
-    additionalLocalFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    preservesValue = false and
-    nodeCand(node2, unbind(config))
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, preservesValue, config, cc) and
+      localFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      nodeCand(node2, unbind(config))
+    )
+    or
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, _, config, cc) and
+      additionalLocalFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      preservesValue = false and
+      nodeCand(node2, unbind(config))
+    )
   )
 }
 
@@ -936,11 +941,11 @@ private predicate localFlowStepPlus(
  * Holds if `node1` can step to `node2` in one or more local steps and this
  * path can occur as a maximal subsequence of local steps in a dataflow path.
  */
-pragma[noinline]
+pragma[nomagic]
 private predicate localFlowBigStep(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext callContext
 ) {
-  localFlowStepPlus(node1, node2, preservesValue, config) and
+  localFlowStepPlus(node1, node2, preservesValue, config, callContext) and
   localFlowExit(node2, config)
 }
 
@@ -1000,7 +1005,7 @@ private class AccessPathFrontNilNode extends Node {
     (
       any(Configuration c).isSource(this)
       or
-      localFlowBigStep(_, this, false, _)
+      localFlowBigStep(_, this, false, _, _)
       or
       additionalJumpStep(_, this, _)
     )
@@ -1023,12 +1028,12 @@ private predicate flowCandFwd0(Node node, boolean fromArg, AccessPathFront apf,
   (
     exists(Node mid |
       flowCandFwd(mid, fromArg, apf, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathFrontNil nil |
       flowCandFwd(mid, fromArg, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       apf = node.(AccessPathFrontNilNode).getApf()
     )
     or
@@ -1122,13 +1127,13 @@ private predicate flowCand0(Node node, boolean toReturn, AccessPathFront apf, Co
   apf instanceof AccessPathFrontNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flowCand(mid, toReturn, apf, config)
   )
   or
   exists(Node mid, AccessPathFrontNil nil |
     flowCandFwd(node, _, apf, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flowCand(mid, toReturn, nil, config) and
     apf instanceof AccessPathFrontNil
   )
@@ -1261,7 +1266,7 @@ abstract private class AccessPath extends TAccessPath {
 
 private class AccessPathNil extends AccessPath, TNil {
   override string toString() {
-    exists(DataFlowType t | this = TNil(t) | result = concat(" : " + ppReprType(t)))
+    exists(DataFlowType t | this = TNil(t) | result = concat(": " + ppReprType(t)))
   }
 
   override AccessPathFront getFront() {
@@ -1277,7 +1282,7 @@ private class AccessPathConsNil extends AccessPathCons, TConsNil {
   override string toString() {
     exists(Content f, DataFlowType t | this = TConsNil(f, t) |
       // The `concat` becomes "" if `ppReprType` has no result.
-      result = f.toString() + concat(" : " + ppReprType(t))
+      result = "[" + f.toString() + "]" + concat(" : " + ppReprType(t))
     )
   }
 
@@ -1294,8 +1299,8 @@ private class AccessPathConsCons extends AccessPathCons, TConsCons {
   override string toString() {
     exists(Content f1, Content f2, int len | this = TConsCons(f1, f2, len) |
       if len = 2
-      then result = f1.toString() + ", " + f2.toString()
-      else result = f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")"
+      then result = "[" + f1.toString() + ", " + f2.toString() + "]"
+      else result = "[" + f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")]"
     )
   }
 
@@ -1363,12 +1368,12 @@ private predicate flowFwd0(
   (
     exists(Node mid |
       flowFwd(mid, fromArg, apf, ap, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathNil nil |
       flowFwd(mid, fromArg, _, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       ap = node.(AccessPathNilNode).getAp() and
       apf = ap.(AccessPathNil).getFront()
     )
@@ -1472,13 +1477,13 @@ private predicate flow0(Node node, boolean toReturn, AccessPath ap, Configuratio
   ap instanceof AccessPathNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flow(mid, toReturn, ap, config)
   )
   or
   exists(Node mid, AccessPathNil nil |
     flowFwd(node, _, _, ap, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flow(mid, toReturn, nil, config) and
     ap instanceof AccessPathNil
   )
@@ -1626,7 +1631,7 @@ abstract class PathNode extends TPathNode {
     this instanceof PathNodeSink and result = ""
     or
     exists(string s | s = this.(PathNodeMid).getAp().toString() |
-      if s = "" then result = "" else result = " [" + s + "]"
+      if s = "" then result = "" else result = " " + s
     )
   }
 
@@ -1729,14 +1734,20 @@ private class PathNodeSink extends PathNode, TPathNodeSink {
  * a callable is recorded by `cc`.
  */
 private predicate pathStep(PathNodeMid mid, Node node, CallContext cc, AccessPath ap) {
-  localFlowBigStep(mid.getNode(), node, true, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  ap = mid.getAp()
-  or
-  localFlowBigStep(mid.getNode(), node, false, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  mid.getAp() instanceof AccessPathNil and
-  ap = node.(AccessPathNilNode).getAp()
+  exists(LocalCallContext localCC, AccessPath ap0, Node midnode, Configuration conf |
+    midnode = mid.getNode() and
+    conf = mid.getConfiguration() and
+    cc = mid.getCallContext() and
+    localCC = getLocalCallContext(cc, midnode.getEnclosingCallable()) and
+    ap0 = mid.getAp()
+  |
+    localFlowBigStep(midnode, node, true, conf, localCC) and
+    ap = ap0
+    or
+    localFlowBigStep(midnode, node, false, conf, localCC) and
+    ap0 instanceof AccessPathNil and
+    ap = node.(AccessPathNilNode).getAp()
+  )
   or
   jumpStep(mid.getNode(), node, mid.getConfiguration()) and
   cc instanceof CallContextAny and
@@ -1880,7 +1891,7 @@ private predicate pathIntoCallable(
     pathIntoCallable0(mid, callable, i, outercc, call, emptyAp) and
     p.isParameterOf(callable, i)
   |
-    if reducedViableImplInCallContext(_, callable, call)
+    if recordDataFlowCallSite(call, callable)
     then innercc = TSpecificCall(call, i, emptyAp)
     else innercc = TSomeCall(p, emptyAp)
   )
@@ -2071,7 +2082,7 @@ private module FlowExploration {
 
   private class PartialAccessPathNil extends PartialAccessPath, TPartialNil {
     override string toString() {
-      exists(DataFlowType t | this = TPartialNil(t) | result = concat(" : " + ppReprType(t)))
+      exists(DataFlowType t | this = TPartialNil(t) | result = concat(": " + ppReprType(t)))
     }
 
     override AccessPathFront getFront() {
@@ -2083,8 +2094,8 @@ private module FlowExploration {
     override string toString() {
       exists(Content f, int len | this = TPartialCons(f, len) |
         if len = 1
-        then result = f.toString()
-        else result = f.toString() + ", ... (" + len.toString() + ")"
+        then result = "[" + f.toString() + "]"
+        else result = "[" + f.toString() + ", ... (" + len.toString() + ")]"
       )
     }
 
@@ -2161,7 +2172,7 @@ private module FlowExploration {
 
     private string ppAp() {
       exists(string s | s = this.(PartialPathNodePriv).getAp().toString() |
-        if s = "" then result = "" else result = " [" + s + "]"
+        if s = "" then result = "" else result = " " + s
       )
     }
 
@@ -2205,16 +2216,19 @@ private module FlowExploration {
   private predicate partialPathStep(
     PartialPathNodePriv mid, Node node, CallContext cc, PartialAccessPath ap, Configuration config
   ) {
-    localFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    ap = mid.getAp() and
-    config = mid.getConfiguration()
-    or
-    additionalLocalFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    mid.getAp() instanceof PartialAccessPathNil and
-    ap = TPartialNil(getErasedRepr(node.getType())) and
-    config = mid.getConfiguration()
+    not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall()) and
+    (
+      localFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      ap = mid.getAp() and
+      config = mid.getConfiguration()
+      or
+      additionalLocalFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      mid.getAp() instanceof PartialAccessPathNil and
+      ap = TPartialNil(getErasedRepr(node.getType())) and
+      config = mid.getConfiguration()
+    )
     or
     jumpStep(mid.getNode(), node, config) and
     cc instanceof CallContextAny and
@@ -2378,7 +2392,7 @@ private module FlowExploration {
       partialPathIntoCallable0(mid, callable, i, outercc, call, emptyAp, ap, config) and
       p.isParameterOf(callable, i)
     |
-      if reducedViableImplInCallContext(_, callable, call)
+      if recordDataFlowCallSite(call, callable)
       then innercc = TSpecificCall(call, i, emptyAp)
       else innercc = TSomeCall(p, emptyAp)
     )

cpp/ql/src/semmle/code/cpp/dataflow/internal/DataFlowImpl4.qll

@@ -905,30 +905,35 @@ private predicate localFlowExit(Node node, Configuration config) {
  */
 pragma[nomagic]
 private predicate localFlowStepPlus(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext cc
 ) {
-  localFlowEntry(node1, config) and
+  not isUnreachableInCall(node2, cc.(LocalCallContextSpecificCall).getCall()) and
   (
-    localFlowStep(node1, node2, config) and preservesValue = true
+    localFlowEntry(node1, config) and
+    (
+      localFlowStep(node1, node2, config) and preservesValue = true
+      or
+      additionalLocalFlowStep(node1, node2, config) and preservesValue = false
+    ) and
+    node1 != node2 and
+    cc.relevantFor(node1.getEnclosingCallable()) and
+    not isUnreachableInCall(node1, cc.(LocalCallContextSpecificCall).getCall()) and
+    nodeCand(node2, unbind(config))
     or
-    additionalLocalFlowStep(node1, node2, config) and preservesValue = false
-  ) and
-  node1 != node2 and
-  nodeCand(node2, unbind(config))
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, preservesValue, config) and
-    localFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    nodeCand(node2, unbind(config))
-  )
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, _, config) and
-    additionalLocalFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    preservesValue = false and
-    nodeCand(node2, unbind(config))
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, preservesValue, config, cc) and
+      localFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      nodeCand(node2, unbind(config))
+    )
+    or
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, _, config, cc) and
+      additionalLocalFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      preservesValue = false and
+      nodeCand(node2, unbind(config))
+    )
   )
 }
 
@@ -936,11 +941,11 @@ private predicate localFlowStepPlus(
  * Holds if `node1` can step to `node2` in one or more local steps and this
  * path can occur as a maximal subsequence of local steps in a dataflow path.
  */
-pragma[noinline]
+pragma[nomagic]
 private predicate localFlowBigStep(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext callContext
 ) {
-  localFlowStepPlus(node1, node2, preservesValue, config) and
+  localFlowStepPlus(node1, node2, preservesValue, config, callContext) and
   localFlowExit(node2, config)
 }
 
@@ -1000,7 +1005,7 @@ private class AccessPathFrontNilNode extends Node {
     (
       any(Configuration c).isSource(this)
       or
-      localFlowBigStep(_, this, false, _)
+      localFlowBigStep(_, this, false, _, _)
       or
       additionalJumpStep(_, this, _)
     )
@@ -1023,12 +1028,12 @@ private predicate flowCandFwd0(Node node, boolean fromArg, AccessPathFront apf,
   (
     exists(Node mid |
       flowCandFwd(mid, fromArg, apf, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathFrontNil nil |
       flowCandFwd(mid, fromArg, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       apf = node.(AccessPathFrontNilNode).getApf()
     )
     or
@@ -1122,13 +1127,13 @@ private predicate flowCand0(Node node, boolean toReturn, AccessPathFront apf, Co
   apf instanceof AccessPathFrontNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flowCand(mid, toReturn, apf, config)
   )
   or
   exists(Node mid, AccessPathFrontNil nil |
     flowCandFwd(node, _, apf, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flowCand(mid, toReturn, nil, config) and
     apf instanceof AccessPathFrontNil
   )
@@ -1261,7 +1266,7 @@ abstract private class AccessPath extends TAccessPath {
 
 private class AccessPathNil extends AccessPath, TNil {
   override string toString() {
-    exists(DataFlowType t | this = TNil(t) | result = concat(" : " + ppReprType(t)))
+    exists(DataFlowType t | this = TNil(t) | result = concat(": " + ppReprType(t)))
   }
 
   override AccessPathFront getFront() {
@@ -1277,7 +1282,7 @@ private class AccessPathConsNil extends AccessPathCons, TConsNil {
   override string toString() {
     exists(Content f, DataFlowType t | this = TConsNil(f, t) |
       // The `concat` becomes "" if `ppReprType` has no result.
-      result = f.toString() + concat(" : " + ppReprType(t))
+      result = "[" + f.toString() + "]" + concat(" : " + ppReprType(t))
     )
   }
 
@@ -1294,8 +1299,8 @@ private class AccessPathConsCons extends AccessPathCons, TConsCons {
   override string toString() {
     exists(Content f1, Content f2, int len | this = TConsCons(f1, f2, len) |
       if len = 2
-      then result = f1.toString() + ", " + f2.toString()
-      else result = f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")"
+      then result = "[" + f1.toString() + ", " + f2.toString() + "]"
+      else result = "[" + f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")]"
     )
   }
 
@@ -1363,12 +1368,12 @@ private predicate flowFwd0(
   (
     exists(Node mid |
       flowFwd(mid, fromArg, apf, ap, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathNil nil |
       flowFwd(mid, fromArg, _, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       ap = node.(AccessPathNilNode).getAp() and
       apf = ap.(AccessPathNil).getFront()
     )
@@ -1472,13 +1477,13 @@ private predicate flow0(Node node, boolean toReturn, AccessPath ap, Configuratio
   ap instanceof AccessPathNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flow(mid, toReturn, ap, config)
   )
   or
   exists(Node mid, AccessPathNil nil |
     flowFwd(node, _, _, ap, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flow(mid, toReturn, nil, config) and
     ap instanceof AccessPathNil
   )
@@ -1626,7 +1631,7 @@ abstract class PathNode extends TPathNode {
     this instanceof PathNodeSink and result = ""
     or
     exists(string s | s = this.(PathNodeMid).getAp().toString() |
-      if s = "" then result = "" else result = " [" + s + "]"
+      if s = "" then result = "" else result = " " + s
     )
   }
 
@@ -1729,14 +1734,20 @@ private class PathNodeSink extends PathNode, TPathNodeSink {
  * a callable is recorded by `cc`.
  */
 private predicate pathStep(PathNodeMid mid, Node node, CallContext cc, AccessPath ap) {
-  localFlowBigStep(mid.getNode(), node, true, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  ap = mid.getAp()
-  or
-  localFlowBigStep(mid.getNode(), node, false, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  mid.getAp() instanceof AccessPathNil and
-  ap = node.(AccessPathNilNode).getAp()
+  exists(LocalCallContext localCC, AccessPath ap0, Node midnode, Configuration conf |
+    midnode = mid.getNode() and
+    conf = mid.getConfiguration() and
+    cc = mid.getCallContext() and
+    localCC = getLocalCallContext(cc, midnode.getEnclosingCallable()) and
+    ap0 = mid.getAp()
+  |
+    localFlowBigStep(midnode, node, true, conf, localCC) and
+    ap = ap0
+    or
+    localFlowBigStep(midnode, node, false, conf, localCC) and
+    ap0 instanceof AccessPathNil and
+    ap = node.(AccessPathNilNode).getAp()
+  )
   or
   jumpStep(mid.getNode(), node, mid.getConfiguration()) and
   cc instanceof CallContextAny and
@@ -1880,7 +1891,7 @@ private predicate pathIntoCallable(
     pathIntoCallable0(mid, callable, i, outercc, call, emptyAp) and
     p.isParameterOf(callable, i)
   |
-    if reducedViableImplInCallContext(_, callable, call)
+    if recordDataFlowCallSite(call, callable)
     then innercc = TSpecificCall(call, i, emptyAp)
     else innercc = TSomeCall(p, emptyAp)
   )
@@ -2071,7 +2082,7 @@ private module FlowExploration {
 
   private class PartialAccessPathNil extends PartialAccessPath, TPartialNil {
     override string toString() {
-      exists(DataFlowType t | this = TPartialNil(t) | result = concat(" : " + ppReprType(t)))
+      exists(DataFlowType t | this = TPartialNil(t) | result = concat(": " + ppReprType(t)))
     }
 
     override AccessPathFront getFront() {
@@ -2083,8 +2094,8 @@ private module FlowExploration {
     override string toString() {
       exists(Content f, int len | this = TPartialCons(f, len) |
         if len = 1
-        then result = f.toString()
-        else result = f.toString() + ", ... (" + len.toString() + ")"
+        then result = "[" + f.toString() + "]"
+        else result = "[" + f.toString() + ", ... (" + len.toString() + ")]"
       )
     }
 
@@ -2161,7 +2172,7 @@ private module FlowExploration {
 
     private string ppAp() {
       exists(string s | s = this.(PartialPathNodePriv).getAp().toString() |
-        if s = "" then result = "" else result = " [" + s + "]"
+        if s = "" then result = "" else result = " " + s
       )
     }
 
@@ -2205,16 +2216,19 @@ private module FlowExploration {
   private predicate partialPathStep(
     PartialPathNodePriv mid, Node node, CallContext cc, PartialAccessPath ap, Configuration config
   ) {
-    localFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    ap = mid.getAp() and
-    config = mid.getConfiguration()
-    or
-    additionalLocalFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    mid.getAp() instanceof PartialAccessPathNil and
-    ap = TPartialNil(getErasedRepr(node.getType())) and
-    config = mid.getConfiguration()
+    not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall()) and
+    (
+      localFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      ap = mid.getAp() and
+      config = mid.getConfiguration()
+      or
+      additionalLocalFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      mid.getAp() instanceof PartialAccessPathNil and
+      ap = TPartialNil(getErasedRepr(node.getType())) and
+      config = mid.getConfiguration()
+    )
     or
     jumpStep(mid.getNode(), node, config) and
     cc instanceof CallContextAny and
@@ -2378,7 +2392,7 @@ private module FlowExploration {
       partialPathIntoCallable0(mid, callable, i, outercc, call, emptyAp, ap, config) and
       p.isParameterOf(callable, i)
     |
-      if reducedViableImplInCallContext(_, callable, call)
+      if recordDataFlowCallSite(call, callable)
       then innercc = TSpecificCall(call, i, emptyAp)
       else innercc = TSomeCall(p, emptyAp)
     )

cpp/ql/src/semmle/code/cpp/dataflow/internal/DataFlowImplCommon.qll

@@ -120,13 +120,16 @@ private module ImplCommon {
         int i, ArgumentNode arg, CallContext outercc, DataFlowCall call
       ) {
         exists(DataFlowCallable c | argumentOf(call, i, arg, c) |
-          outercc = TAnyCallContext()
-          or
-          outercc = TSomeCall(getAParameter(c), _)
-          or
-          exists(DataFlowCall other | outercc = TSpecificCall(other, _, _) |
-            reducedViableImplInCallContext(_, c, other)
-          )
+          (
+            outercc = TAnyCallContext()
+            or
+            outercc = TSomeCall(getAParameter(c), _)
+            or
+            exists(DataFlowCall other | outercc = TSpecificCall(other, _, _) |
+              recordDataFlowCallSite(other, c)
+            )
+          ) and
+          not isUnreachableInCall(arg, outercc.(CallContextSpecificCall).getCall())
         )
       }
 
@@ -152,7 +155,7 @@ private module ImplCommon {
         exists(int i, DataFlowCallable callable |
           viableParamArg1(p, callable, i, arg, outercc, call)
         |
-          if reducedViableImplInCallContext(_, callable, call)
+          if recordDataFlowCallSite(call, callable)
           then innercc = TSpecificCall(call, i, true)
           else innercc = TSomeCall(p, true)
         )
@@ -164,7 +167,7 @@ private module ImplCommon {
         exists(DataFlowCall call, int i, DataFlowCallable callable |
           result = TSpecificCall(call, i, _) and
           p.isParameterOf(callable, i) and
-          reducedViableImplInCallContext(_, callable, call)
+          recordDataFlowCallSite(call, callable)
         )
       }
 
@@ -180,14 +183,16 @@ private module ImplCommon {
         exists(Node mid |
           parameterValueFlow(p, mid, cc) and
           step(mid, node) and
-          compatibleTypes(p.getType(), node.getType())
+          compatibleTypes(p.getType(), node.getType()) and
+          not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall())
         )
         or
         // flow through a callable
         exists(Node arg |
           parameterValueFlow(p, arg, cc) and
           argumentValueFlowsThrough(arg, node, cc) and
-          compatibleTypes(p.getType(), node.getType())
+          compatibleTypes(p.getType(), node.getType()) and
+          not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall())
         )
       }
 
@@ -220,6 +225,7 @@ private module ImplCommon {
           argumentValueFlowsThrough0(call, arg, kind, cc)
         |
           out = getAnOutNode(call, kind) and
+          not isUnreachableInCall(out, cc.(CallContextSpecificCall).getCall()) and
           compatibleTypes(arg.getType(), out.getType())
         )
       }
@@ -462,13 +468,16 @@ private module ImplCommon {
         int i, ArgumentNode arg, CallContext outercc, DataFlowCall call
       ) {
         exists(DataFlowCallable c | argumentOf(call, i, arg, c) |
-          outercc = TAnyCallContext()
-          or
-          outercc = TSomeCall(getAParameter(c), _)
-          or
-          exists(DataFlowCall other | outercc = TSpecificCall(other, _, _) |
-            reducedViableImplInCallContext(_, c, other)
-          )
+          (
+            outercc = TAnyCallContext()
+            or
+            outercc = TSomeCall(getAParameter(c), _)
+            or
+            exists(DataFlowCall other | outercc = TSpecificCall(other, _, _) |
+              recordDataFlowCallSite(other, c)
+            )
+          ) and
+          not isUnreachableInCall(arg, outercc.(CallContextSpecificCall).getCall())
         )
       }
 
@@ -494,7 +503,7 @@ private module ImplCommon {
         exists(int i, DataFlowCallable callable |
           viableParamArg1(p, callable, i, arg, outercc, call)
         |
-          if reducedViableImplInCallContext(_, callable, call)
+          if recordDataFlowCallSite(call, callable)
           then innercc = TSpecificCall(call, i, true)
           else innercc = TSomeCall(p, true)
         )
@@ -506,7 +515,7 @@ private module ImplCommon {
         exists(DataFlowCall call, int i, DataFlowCallable callable |
           result = TSpecificCall(call, i, _) and
           p.isParameterOf(callable, i) and
-          reducedViableImplInCallContext(_, callable, call)
+          recordDataFlowCallSite(call, callable)
         )
       }
 
@@ -522,14 +531,16 @@ private module ImplCommon {
         exists(Node mid |
           parameterValueFlow(p, mid, cc) and
           step(mid, node) and
-          compatibleTypes(p.getType(), node.getType())
+          compatibleTypes(p.getType(), node.getType()) and
+          not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall())
         )
         or
         // flow through a callable
         exists(Node arg |
           parameterValueFlow(p, arg, cc) and
           argumentValueFlowsThrough(arg, node, cc) and
-          compatibleTypes(p.getType(), node.getType())
+          compatibleTypes(p.getType(), node.getType()) and
+          not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall())
         )
       }
 
@@ -562,6 +573,7 @@ private module ImplCommon {
           argumentValueFlowsThrough0(call, arg, kind, cc)
         |
           out = getAnOutNode(call, kind) and
+          not isUnreachableInCall(out, cc.(CallContextSpecificCall).getCall()) and
           compatibleTypes(arg.getType(), out.getType())
         )
       }
@@ -575,11 +587,22 @@ private module ImplCommon {
       exists(ArgumentNode arg | arg.argumentOf(call, -1))
     }
 
+    /**
+     * Holds if the call context `call` either improves virtual dispatch in
+     * `callable` or if it allows us to prune unreachable nodes in `callable`.
+     */
+    cached
+    predicate recordDataFlowCallSite(DataFlowCall call, DataFlowCallable callable) {
+      reducedViableImplInCallContext(_, callable, call)
+      or
+      exists(Node n | n.getEnclosingCallable() = callable | isUnreachableInCall(n, call))
+    }
+
     cached
     newtype TCallContext =
       TAnyCallContext() or
       TSpecificCall(DataFlowCall call, int i, boolean emptyAp) {
-        reducedViableImplInCallContext(_, _, call) and
+        recordDataFlowCallSite(call, _) and
         (emptyAp = true or emptyAp = false) and
         (
           exists(call.getArgument(i))
@@ -593,6 +616,11 @@ private module ImplCommon {
     cached
     newtype TReturnPosition =
       TReturnPosition0(DataFlowCallable c, ReturnKind kind) { returnPosition(_, c, kind) }
+
+    cached
+    newtype TLocalFlowCallContext =
+      TAnyLocalCall() or
+      TSpecificLocalCall(DataFlowCall call) { isUnreachableInCall(_, call) }
   }
 
   pragma[noinline]
@@ -602,14 +630,15 @@ private module ImplCommon {
   }
 
   /**
-   * A call context to restrict the targets of virtual dispatch and match the
-   * call sites of flow into a method with flow out of a method.
+   * A call context to restrict the targets of virtual dispatch, prune local flow,
+   * and match the call sites of flow into a method with flow out of a method.
    *
    * There are four cases:
    * - `TAnyCallContext()` : No restrictions on method flow.
    * - `TSpecificCall(DataFlowCall call, int i)` : Flow entered through the `i`th
    *    parameter at the given `call`. This call improves the set of viable
-   *    dispatch targets for at least one method call in the current callable.
+   *    dispatch targets for at least one method call in the current callable
+   *    or helps prune unreachable nodes in the current callable.
    * - `TSomeCall(ParameterNode p)` : Flow entered through parameter `p`. The
    *    originating call does not improve the set of dispatch targets for any
    *    method call in the current callable and was therefore not recorded.
@@ -619,10 +648,15 @@ private module ImplCommon {
    */
   abstract class CallContext extends TCallContext {
     abstract string toString();
+
+    /** Holds if this call context is relevant for `callable`. */
+    abstract predicate relevantFor(DataFlowCallable callable);
   }
 
   class CallContextAny extends CallContext, TAnyCallContext {
     override string toString() { result = "CcAny" }
+
+    override predicate relevantFor(DataFlowCallable callable) { any() }
   }
 
   abstract class CallContextCall extends CallContext { }
@@ -633,16 +667,73 @@ private module ImplCommon {
         result = "CcCall(" + call + ", " + i + ")"
       )
     }
+
+    override predicate relevantFor(DataFlowCallable callable) {
+      recordDataFlowCallSite(getCall(), callable)
+    }
+
+    DataFlowCall getCall() { this = TSpecificCall(result, _, _) }
   }
 
   class CallContextSomeCall extends CallContextCall, TSomeCall {
     override string toString() { result = "CcSomeCall" }
+
+    override predicate relevantFor(DataFlowCallable callable) {
+      exists(ParameterNode p | this = TSomeCall(p, _) and p.getEnclosingCallable() = callable)
+    }
   }
 
   class CallContextReturn extends CallContext, TReturn {
     override string toString() {
       exists(DataFlowCall call | this = TReturn(_, call) | result = "CcReturn(" + call + ")")
     }
+
+    override predicate relevantFor(DataFlowCallable callable) {
+      exists(DataFlowCall call | this = TReturn(_, call) and call.getEnclosingCallable() = callable)
+    }
+  }
+
+  /**
+   * A call context that is relevant for pruning local flow.
+   */
+  abstract class LocalCallContext extends TLocalFlowCallContext {
+    abstract string toString();
+
+    /** Holds if this call context is relevant for `callable`. */
+    abstract predicate relevantFor(DataFlowCallable callable);
+  }
+
+  class LocalCallContextAny extends LocalCallContext, TAnyLocalCall {
+    override string toString() { result = "LocalCcAny" }
+
+    override predicate relevantFor(DataFlowCallable callable) { any() }
+  }
+
+  class LocalCallContextSpecificCall extends LocalCallContext, TSpecificLocalCall {
+    LocalCallContextSpecificCall() { this = TSpecificLocalCall(call) }
+
+    DataFlowCall call;
+
+    DataFlowCall getCall() { result = call }
+
+    override string toString() { result = "LocalCcCall(" + call + ")" }
+
+    override predicate relevantFor(DataFlowCallable callable) { relevantLocalCCtx(call, callable) }
+  }
+
+  private predicate relevantLocalCCtx(DataFlowCall call, DataFlowCallable callable) {
+    exists(Node n | n.getEnclosingCallable() = callable and isUnreachableInCall(n, call))
+  }
+
+  /**
+   * Gets the local call context given the call context and the callable that
+   * the contexts apply to.
+   */
+  LocalCallContext getLocalCallContext(CallContext ctx, DataFlowCallable callable) {
+    ctx.relevantFor(callable) and
+    if relevantLocalCCtx(ctx.(CallContextSpecificCall).getCall(), callable)
+    then result.(LocalCallContextSpecificCall).getCall() = ctx.(CallContextSpecificCall).getCall()
+    else result instanceof LocalCallContextAny
   }
 
   /** A callable tagged with a relevant return kind. */

cpp/ql/src/semmle/code/cpp/dataflow/internal/DataFlowImplLocal.qll

@@ -905,30 +905,35 @@ private predicate localFlowExit(Node node, Configuration config) {
  */
 pragma[nomagic]
 private predicate localFlowStepPlus(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext cc
 ) {
-  localFlowEntry(node1, config) and
+  not isUnreachableInCall(node2, cc.(LocalCallContextSpecificCall).getCall()) and
   (
-    localFlowStep(node1, node2, config) and preservesValue = true
+    localFlowEntry(node1, config) and
+    (
+      localFlowStep(node1, node2, config) and preservesValue = true
+      or
+      additionalLocalFlowStep(node1, node2, config) and preservesValue = false
+    ) and
+    node1 != node2 and
+    cc.relevantFor(node1.getEnclosingCallable()) and
+    not isUnreachableInCall(node1, cc.(LocalCallContextSpecificCall).getCall()) and
+    nodeCand(node2, unbind(config))
     or
-    additionalLocalFlowStep(node1, node2, config) and preservesValue = false
-  ) and
-  node1 != node2 and
-  nodeCand(node2, unbind(config))
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, preservesValue, config) and
-    localFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    nodeCand(node2, unbind(config))
-  )
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, _, config) and
-    additionalLocalFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    preservesValue = false and
-    nodeCand(node2, unbind(config))
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, preservesValue, config, cc) and
+      localFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      nodeCand(node2, unbind(config))
+    )
+    or
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, _, config, cc) and
+      additionalLocalFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      preservesValue = false and
+      nodeCand(node2, unbind(config))
+    )
   )
 }
 
@@ -936,11 +941,11 @@ private predicate localFlowStepPlus(
  * Holds if `node1` can step to `node2` in one or more local steps and this
  * path can occur as a maximal subsequence of local steps in a dataflow path.
  */
-pragma[noinline]
+pragma[nomagic]
 private predicate localFlowBigStep(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext callContext
 ) {
-  localFlowStepPlus(node1, node2, preservesValue, config) and
+  localFlowStepPlus(node1, node2, preservesValue, config, callContext) and
   localFlowExit(node2, config)
 }
 
@@ -1000,7 +1005,7 @@ private class AccessPathFrontNilNode extends Node {
     (
       any(Configuration c).isSource(this)
       or
-      localFlowBigStep(_, this, false, _)
+      localFlowBigStep(_, this, false, _, _)
       or
       additionalJumpStep(_, this, _)
     )
@@ -1023,12 +1028,12 @@ private predicate flowCandFwd0(Node node, boolean fromArg, AccessPathFront apf,
   (
     exists(Node mid |
       flowCandFwd(mid, fromArg, apf, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathFrontNil nil |
       flowCandFwd(mid, fromArg, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       apf = node.(AccessPathFrontNilNode).getApf()
     )
     or
@@ -1122,13 +1127,13 @@ private predicate flowCand0(Node node, boolean toReturn, AccessPathFront apf, Co
   apf instanceof AccessPathFrontNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flowCand(mid, toReturn, apf, config)
   )
   or
   exists(Node mid, AccessPathFrontNil nil |
     flowCandFwd(node, _, apf, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flowCand(mid, toReturn, nil, config) and
     apf instanceof AccessPathFrontNil
   )
@@ -1261,7 +1266,7 @@ abstract private class AccessPath extends TAccessPath {
 
 private class AccessPathNil extends AccessPath, TNil {
   override string toString() {
-    exists(DataFlowType t | this = TNil(t) | result = concat(" : " + ppReprType(t)))
+    exists(DataFlowType t | this = TNil(t) | result = concat(": " + ppReprType(t)))
   }
 
   override AccessPathFront getFront() {
@@ -1277,7 +1282,7 @@ private class AccessPathConsNil extends AccessPathCons, TConsNil {
   override string toString() {
     exists(Content f, DataFlowType t | this = TConsNil(f, t) |
       // The `concat` becomes "" if `ppReprType` has no result.
-      result = f.toString() + concat(" : " + ppReprType(t))
+      result = "[" + f.toString() + "]" + concat(" : " + ppReprType(t))
     )
   }
 
@@ -1294,8 +1299,8 @@ private class AccessPathConsCons extends AccessPathCons, TConsCons {
   override string toString() {
     exists(Content f1, Content f2, int len | this = TConsCons(f1, f2, len) |
       if len = 2
-      then result = f1.toString() + ", " + f2.toString()
-      else result = f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")"
+      then result = "[" + f1.toString() + ", " + f2.toString() + "]"
+      else result = "[" + f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")]"
     )
   }
 
@@ -1363,12 +1368,12 @@ private predicate flowFwd0(
   (
     exists(Node mid |
       flowFwd(mid, fromArg, apf, ap, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathNil nil |
       flowFwd(mid, fromArg, _, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       ap = node.(AccessPathNilNode).getAp() and
       apf = ap.(AccessPathNil).getFront()
     )
@@ -1472,13 +1477,13 @@ private predicate flow0(Node node, boolean toReturn, AccessPath ap, Configuratio
   ap instanceof AccessPathNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flow(mid, toReturn, ap, config)
   )
   or
   exists(Node mid, AccessPathNil nil |
     flowFwd(node, _, _, ap, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flow(mid, toReturn, nil, config) and
     ap instanceof AccessPathNil
   )
@@ -1626,7 +1631,7 @@ abstract class PathNode extends TPathNode {
     this instanceof PathNodeSink and result = ""
     or
     exists(string s | s = this.(PathNodeMid).getAp().toString() |
-      if s = "" then result = "" else result = " [" + s + "]"
+      if s = "" then result = "" else result = " " + s
     )
   }
 
@@ -1729,14 +1734,20 @@ private class PathNodeSink extends PathNode, TPathNodeSink {
  * a callable is recorded by `cc`.
  */
 private predicate pathStep(PathNodeMid mid, Node node, CallContext cc, AccessPath ap) {
-  localFlowBigStep(mid.getNode(), node, true, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  ap = mid.getAp()
-  or
-  localFlowBigStep(mid.getNode(), node, false, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  mid.getAp() instanceof AccessPathNil and
-  ap = node.(AccessPathNilNode).getAp()
+  exists(LocalCallContext localCC, AccessPath ap0, Node midnode, Configuration conf |
+    midnode = mid.getNode() and
+    conf = mid.getConfiguration() and
+    cc = mid.getCallContext() and
+    localCC = getLocalCallContext(cc, midnode.getEnclosingCallable()) and
+    ap0 = mid.getAp()
+  |
+    localFlowBigStep(midnode, node, true, conf, localCC) and
+    ap = ap0
+    or
+    localFlowBigStep(midnode, node, false, conf, localCC) and
+    ap0 instanceof AccessPathNil and
+    ap = node.(AccessPathNilNode).getAp()
+  )
   or
   jumpStep(mid.getNode(), node, mid.getConfiguration()) and
   cc instanceof CallContextAny and
@@ -1880,7 +1891,7 @@ private predicate pathIntoCallable(
     pathIntoCallable0(mid, callable, i, outercc, call, emptyAp) and
     p.isParameterOf(callable, i)
   |
-    if reducedViableImplInCallContext(_, callable, call)
+    if recordDataFlowCallSite(call, callable)
     then innercc = TSpecificCall(call, i, emptyAp)
     else innercc = TSomeCall(p, emptyAp)
   )
@@ -2071,7 +2082,7 @@ private module FlowExploration {
 
   private class PartialAccessPathNil extends PartialAccessPath, TPartialNil {
     override string toString() {
-      exists(DataFlowType t | this = TPartialNil(t) | result = concat(" : " + ppReprType(t)))
+      exists(DataFlowType t | this = TPartialNil(t) | result = concat(": " + ppReprType(t)))
     }
 
     override AccessPathFront getFront() {
@@ -2083,8 +2094,8 @@ private module FlowExploration {
     override string toString() {
       exists(Content f, int len | this = TPartialCons(f, len) |
         if len = 1
-        then result = f.toString()
-        else result = f.toString() + ", ... (" + len.toString() + ")"
+        then result = "[" + f.toString() + "]"
+        else result = "[" + f.toString() + ", ... (" + len.toString() + ")]"
       )
     }
 
@@ -2161,7 +2172,7 @@ private module FlowExploration {
 
     private string ppAp() {
       exists(string s | s = this.(PartialPathNodePriv).getAp().toString() |
-        if s = "" then result = "" else result = " [" + s + "]"
+        if s = "" then result = "" else result = " " + s
       )
     }
 
@@ -2205,16 +2216,19 @@ private module FlowExploration {
   private predicate partialPathStep(
     PartialPathNodePriv mid, Node node, CallContext cc, PartialAccessPath ap, Configuration config
   ) {
-    localFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    ap = mid.getAp() and
-    config = mid.getConfiguration()
-    or
-    additionalLocalFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    mid.getAp() instanceof PartialAccessPathNil and
-    ap = TPartialNil(getErasedRepr(node.getType())) and
-    config = mid.getConfiguration()
+    not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall()) and
+    (
+      localFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      ap = mid.getAp() and
+      config = mid.getConfiguration()
+      or
+      additionalLocalFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      mid.getAp() instanceof PartialAccessPathNil and
+      ap = TPartialNil(getErasedRepr(node.getType())) and
+      config = mid.getConfiguration()
+    )
     or
     jumpStep(mid.getNode(), node, config) and
     cc instanceof CallContextAny and
@@ -2378,7 +2392,7 @@ private module FlowExploration {
       partialPathIntoCallable0(mid, callable, i, outercc, call, emptyAp, ap, config) and
       p.isParameterOf(callable, i)
     |
-      if reducedViableImplInCallContext(_, callable, call)
+      if recordDataFlowCallSite(call, callable)
       then innercc = TSpecificCall(call, i, emptyAp)
       else innercc = TSomeCall(p, emptyAp)
     )

cpp/ql/src/semmle/code/cpp/dataflow/internal/DataFlowPrivate.qll

@@ -51,7 +51,9 @@ class ArgumentNode extends Node {
   DataFlowCall getCall() { this.argumentOf(result, _) }
 }
 
-private newtype TReturnKind = TNormalReturnKind()
+private newtype TReturnKind =
+  TNormalReturnKind() or
+  TRefReturnKind(int i) { exists(Parameter parameter | i = parameter.getIndex()) }
 
 /**
  * A return kind. A return kind describes how a value can be returned
@@ -59,23 +61,54 @@ private newtype TReturnKind = TNormalReturnKind()
  */
 class ReturnKind extends TReturnKind {
   /** Gets a textual representation of this return kind. */
-  string toString() { result = "return" }
+  string toString() {
+    this instanceof TNormalReturnKind and
+    result = "return"
+    or
+    this instanceof TRefReturnKind and
+    result = "ref"
+  }
 }
 
-/** A data flow node that occurs as the result of a `ReturnStmt`. */
-class ReturnNode extends ExprNode {
-  ReturnNode() { exists(ReturnStmt ret | this.getExpr() = ret.getExpr()) }
+/** A data flow node that represents a returned value in the called function. */
+abstract class ReturnNode extends Node {
+  /** Gets the kind of this returned value. */
+  abstract ReturnKind getKind();
+}
+
+/** A `ReturnNode` that occurs as the result of a `ReturnStmt`. */
+private class NormalReturnNode extends ReturnNode, ExprNode {
+  NormalReturnNode() { exists(ReturnStmt ret | this.getExpr() = ret.getExpr()) }
 
   /** Gets the kind of this returned value. */
-  ReturnKind getKind() { result = TNormalReturnKind() }
+  override ReturnKind getKind() { result = TNormalReturnKind() }
 }
 
-/** A data flow node that represents the output of a call. */
-class OutNode extends ExprNode {
-  OutNode() { this.getExpr() instanceof Call }
+/**
+ * A `ReturnNode` that occurs as a result of a definition of a reference
+ * parameter reaching the end of a function body.
+ */
+private class RefReturnNode extends ReturnNode, RefParameterFinalValueNode {
+  /** Gets the kind of this returned value. */
+  override ReturnKind getKind() { result = TRefReturnKind(this.getParameter().getIndex()) }
+}
+
+/** A data flow node that represents the output of a call at the call site. */
+abstract class OutNode extends Node {
+  /** Gets the underlying call. */
+  abstract DataFlowCall getCall();
+}
+
+private class ExprOutNode extends OutNode, ExprNode {
+  ExprOutNode() { this.getExpr() instanceof Call }
 
   /** Gets the underlying call. */
-  DataFlowCall getCall() { result = this.getExpr() }
+  override DataFlowCall getCall() { result = this.getExpr() }
+}
+
+private class RefOutNode extends OutNode, DefinitionByReferenceNode {
+  /** Gets the underlying call. */
+  override DataFlowCall getCall() { result = this.getArgument().getParent() }
 }
 
 /**
@@ -85,6 +118,11 @@ class OutNode extends ExprNode {
 OutNode getAnOutNode(DataFlowCall call, ReturnKind kind) {
   result = call.getNode() and
   kind = TNormalReturnKind()
+  or
+  exists(int i |
+    result.asDefiningArgument() = call.getArgument(i) and
+    kind = TRefReturnKind(i)
+  )
 }
 
 /**
@@ -264,3 +302,5 @@ class DataFlowCall extends Expr {
   /** Gets the enclosing callable of this call. */
   Function getEnclosingCallable() { result = this.getEnclosingFunction() }
 }
+
+predicate isUnreachableInCall(Node n, DataFlowCall call) { none() } // stub implementation

cpp/ql/src/semmle/code/cpp/dataflow/internal/DataFlowUtil.qll

@@ -5,6 +5,8 @@
 private import cpp
 private import semmle.code.cpp.dataflow.internal.FlowVar
 private import semmle.code.cpp.models.interfaces.DataFlow
+private import semmle.code.cpp.controlflow.Guards
+private import semmle.code.cpp.valuenumbering.GlobalValueNumbering
 
 cached
 private newtype TNode =
@@ -25,7 +27,8 @@ private newtype TNode =
       not c.getTarget().getParameter(i).getUnderlyingType().(PointerType).getBaseType().isConst()
     )
   } or
-  TUninitializedNode(LocalVariable v) { not v.hasInitializer() }
+  TUninitializedNode(LocalVariable v) { not v.hasInitializer() } or
+  TRefParameterFinalValueNode(Parameter p) { exists(FlowVar var | var.reachesRefParameter(p)) }
 
 /**
  * A node in a data flow graph.
@@ -248,6 +251,23 @@ class UninitializedNode extends Node, TUninitializedNode {
   LocalVariable getLocalVariable() { result = v }
 }
 
+/** INTERNAL: do not use. The final value of a non-const ref parameter. */
+class RefParameterFinalValueNode extends Node, TRefParameterFinalValueNode {
+  Parameter p;
+
+  RefParameterFinalValueNode() { this = TRefParameterFinalValueNode(p) }
+
+  override Function getFunction() { result = p.getFunction() }
+
+  override Type getType() { result = p.getType() }
+
+  override string toString() { result = p.toString() }
+
+  override Location getLocation() { result = p.getLocation() }
+
+  Parameter getParameter() { result = p }
+}
+
 /**
  * A node associated with an object after an operation that might have
  * changed its state.
@@ -490,7 +510,7 @@ predicate simpleLocalFlowStep(Node nodeFrom, Node nodeTo) {
       or
       var.definedPartiallyAt(nodeFrom.asPartialDefinition())
     ) and
-    varToExprStep(var, nodeTo.asExpr())
+    varToNodeStep(var, nodeTo)
   )
   or
   // Expr -> DefinitionByReferenceNode
@@ -533,9 +553,13 @@ private predicate exprToVarStep(Expr assignedExpr, FlowVar var) {
 }
 
 /**
- * Holds if the expression `e` is an access of the variable `var`.
+ * Holds if the node `n` is an access of the variable `var`.
  */
-private predicate varToExprStep(FlowVar var, Expr e) { e = var.getAnAccess() }
+private predicate varToNodeStep(FlowVar var, Node n) {
+  n.asExpr() = var.getAnAccess()
+  or
+  var.reachesRefParameter(n.(RefParameterFinalValueNode).getParameter())
+}
 
 /**
  * Holds if data flows from `fromExpr` to `toExpr` directly, in the case
@@ -658,12 +682,16 @@ VariableAccess getAnAccessToAssignedVariable(Expr assign) {
  *
  * It is important that all extending classes in scope are disjoint.
  */
-class BarrierGuard extends Expr {
-  /** NOT YET SUPPORTED. Holds if this guard validates `e` upon evaluating to `branch`. */
-  abstract deprecated predicate checks(Expr e, boolean branch);
+class BarrierGuard extends GuardCondition {
+  /** Override this predicate to hold if this guard validates `e` upon evaluating to `b`. */
+  abstract predicate checks(Expr e, boolean b);
 
   /** Gets a node guarded by this guard. */
-  final Node getAGuardedNode() {
-    none() // stub
+  final ExprNode getAGuardedNode() {
+    exists(GVN value, boolean branch |
+      result.getExpr() = value.getAnExpr() and
+      this.checks(value.getAnExpr(), branch) and
+      this.controls(result.getExpr().getBasicBlock(), branch)
+    )
   }
 }

cpp/ql/src/semmle/code/cpp/dataflow/internal/FlowVar.qll

@@ -62,9 +62,20 @@ class FlowVar extends TFlowVar {
   cached
   abstract predicate definedByReference(Expr arg);
 
+  /**
+   * Holds if this `FlowVar` is a `PartialDefinition` whose defined expression
+   * is `e`.
+   */
   cached
   abstract predicate definedPartiallyAt(Expr e);
 
+  /**
+   * Holds if this `FlowVar` is a definition of a reference parameter `p` that
+   * persists until the function returns.
+   */
+  cached
+  abstract predicate reachesRefParameter(Parameter p);
+
   /**
    * Holds if this `FlowVar` corresponds to the initial value of `v`. The following
    * is an exhaustive list of cases where this may happen.
@@ -338,6 +349,9 @@ module FlowVar_internal {
       param = v
     }
 
+    // `fullySupportedSsaVariable` excludes reference types
+    override predicate reachesRefParameter(Parameter p) { none() }
+
     /**
      * Holds if this `SsaVar` corresponds to a non-phi definition. Users of this
      * library will never directly use an `SsaVar` that comes from a phi node,
@@ -387,6 +401,13 @@ module FlowVar_internal {
       sbb = v.(Parameter).getFunction().getEntryPoint()
     }
 
+    override predicate reachesRefParameter(Parameter p) {
+      parameterIsNonConstReference(p) and
+      p = v and
+      // This definition reaches the exit node of the function CFG
+      getAReachedBlockVarSBB(this).getANode() = p.getFunction()
+    }
+
     override predicate definedByInitialValue(LocalScopeVariable lsv) {
       blockVarDefinedByVariable(sbb, lsv) and
       lsv = v
@@ -490,7 +511,7 @@ module FlowVar_internal {
       exists(VariableAccess va |
         va.getTarget() = result and
         readAccess(va) and
-        bbNotInLoop(va.getBasicBlock())
+        exists(BasicBlock bb | bb = va.getBasicBlock() | not this.bbInLoop(bb))
       )
     }
 
@@ -513,10 +534,8 @@ module FlowVar_internal {
       bbInLoopCondition(bb)
     }
 
-    predicate bbNotInLoop(BasicBlock bb) {
-      not this.bbInLoop(bb) and
-      bb.getEnclosingFunction() = this.getEnclosingFunction()
-    }
+    /** Holds if `sbb` is inside this loop. */
+    predicate sbbInLoop(SubBasicBlock sbb) { this.bbInLoop(sbb.getBasicBlock()) }
 
     /**
      * Holds if `bb` is a basic block inside this loop where `v` has not been
@@ -537,22 +556,19 @@ module FlowVar_internal {
   }
 
   /**
-   * Holds if some loop always assigns to `v` before leaving through an edge
-   * from `bbInside` in its condition to `bbOutside` outside the loop, where
-   * (`sbbDef`, `v`) is a `BlockVar` defined outside the loop. Also, `v` must
-   * be used outside the loop.
+   * Holds if `loop` always assigns to `v` before leaving through an edge
+   * from `bbInside` in its condition to `bbOutside` outside the loop. Also,
+   * `v` must be used outside the loop.
    */
   predicate skipLoop(
-    SubBasicBlock sbbInside, SubBasicBlock sbbOutside, SubBasicBlock sbbDef, Variable v
+    SubBasicBlock sbbInside, SubBasicBlock sbbOutside, Variable v, AlwaysTrueUponEntryLoop loop
   ) {
-    exists(AlwaysTrueUponEntryLoop loop, BasicBlock bbInside, BasicBlock bbOutside |
+    exists(BasicBlock bbInside, BasicBlock bbOutside |
       loop.alwaysAssignsBeforeLeavingCondition(bbInside, bbOutside, v) and
       bbInside = sbbInside.getBasicBlock() and
       bbOutside = sbbOutside.getBasicBlock() and
       sbbInside.lastInBB() and
-      sbbOutside.firstInBB() and
-      loop.bbNotInLoop(sbbDef.getBasicBlock()) and
-      exists(TBlockVar(sbbDef, v))
+      sbbOutside.firstInBB()
     )
   }
 
@@ -571,7 +587,7 @@ module FlowVar_internal {
       start = TBlockVar(sbbDef, v) and
       result = mid.getASuccessor() and
       variableLiveInSBB(result, v) and
-      not skipLoop(mid, result, sbbDef, v) and
+      forall(AlwaysTrueUponEntryLoop loop | skipLoop(mid, result, v, loop) | loop.sbbInLoop(sbbDef)) and
       not assignmentLikeOperation(result, v, _, _)
     )
   }
@@ -593,12 +609,23 @@ module FlowVar_internal {
   private predicate variableLiveInSBB(SubBasicBlock sbb, Variable v) {
     variableAccessInSBB(v, sbb, _)
     or
+    // Non-const reference parameters are live at the end of the function
+    parameterIsNonConstReference(v) and
+    sbb.contains(v.(Parameter).getFunction())
+    or
     exists(SubBasicBlock succ | succ = sbb.getASuccessor() |
       variableLiveInSBB(succ, v) and
       not variableNotLiveBefore(succ, v)
     )
   }
 
+  predicate parameterIsNonConstReference(Parameter p) {
+    exists(ReferenceType refType |
+      refType = p.getUnderlyingType() and
+      not refType.getBaseType().isConst()
+    )
+  }
+
   /**
    * Holds if liveness of `v` should stop propagating backwards from `sbb`.
    */
@@ -679,10 +706,11 @@ module FlowVar_internal {
   predicate dominatedByOverwrite(UninitializedLocalVariable v, VariableAccess va) {
     exists(BasicBlock bb, int vaIndex |
       va = bb.getNode(vaIndex) and
-      va.getTarget() = v
-    |
+      va.getTarget() = v and
       vaIndex > indexOfFirstOverwriteInBB(v, bb)
       or
+      va = bb.getNode(vaIndex) and
+      va.getTarget() = v and
       bbStrictlyDominates(getAnOverwritingBB(v), bb)
     )
   }

cpp/ql/src/semmle/code/cpp/dispatch/VirtualDispatch.qll

@@ -0,0 +1,87 @@
+import cpp
+
+/**
+ * A module for performing simple virtual dispatch analysis.
+ */
+module VirtualDispatch {
+  /**
+   * Gets a possible implementation target when the given function is the static target of a virtual call.
+   */
+  private MemberFunction getAPossibleImplementation(MemberFunction staticTarget) {
+    /*
+     * `IUnknown` is a COM interface with many sub-types, and many overrides (tens of thousands on
+     * some databases), so we ignore any member functions defined within that interface.
+     */
+
+    not staticTarget.getDeclaringType().hasName("IUnknown") and
+    result = staticTarget.getAnOverridingFunction*()
+  }
+
+  /** Gets the static type of the qualifier expression for the given call. */
+  private Class getCallQualifierType(FunctionCall c) {
+    result = c.getQualifier().getType().stripType() and
+    /*
+     * `IUnknown` is a COM interface with many sub-types (tens of thousands on some databases), so
+     * we ignore any cases where the qualifier type is that interface.
+     */
+
+    not result.hasName("IUnknown")
+  }
+
+  /**
+   * Helper predicate for `getAViableTarget`, which computes the viable targets for
+   * virtual calls based on the qualifier type.
+   */
+  private Function getAViableVirtualCallTarget(Class qualifierType, MemberFunction staticTarget) {
+    exists(Class qualifierSubType |
+      result = getAPossibleImplementation(staticTarget) and
+      qualifierType = qualifierSubType.getABaseClass*() and
+      mayInherit(qualifierSubType, result) and
+      not cannotInherit(qualifierSubType, result)
+    )
+  }
+
+  /**
+   * Gets a viable target for the given function call.
+   *
+   * If `c` is a virtual call, then we will perform a simple virtual dispatch analysis to return
+   * the `Function` instances which might be a viable target, based on an analysis of the declared
+   * type of the qualifier expression.
+   *
+   * (This analysis is imprecise: it looks for subtypes of the declared type of the qualifier expression
+   * and the possible implementations of `c.getTarget()` that are declared or inherited by those subtypes.
+   * This does not account for virtual inheritance and the ways this affects dispatch.)
+   *
+   * If `c` is not a virtual call, the result will be `c.getTarget()`.
+   */
+  Function getAViableTarget(Call c) {
+    if c.(FunctionCall).isVirtual() and c.getTarget() instanceof MemberFunction
+    then result = getAViableVirtualCallTarget(getCallQualifierType(c), c.getTarget())
+    else result = c.getTarget()
+  }
+
+  /** Holds if `f` is declared in `c` or a transitive base class of `c`. */
+  private predicate mayInherit(Class c, MemberFunction f) {
+    f.getDeclaringType() = c.getABaseClass*()
+  }
+
+  /**
+   * Holds if `c` cannot inherit the member function `f`,
+   * i.e. `c` or one of its supertypes overrides `f`.
+   */
+  private predicate cannotInherit(Class c, MemberFunction f) {
+    exists(Class overridingType, MemberFunction override |
+      cannotInheritHelper(c, f, overridingType, override) and
+      override.overrides+(f)
+    )
+  }
+
+  pragma[noinline]
+  private predicate cannotInheritHelper(
+    Class c, MemberFunction f, Class overridingType, MemberFunction override
+  ) {
+    c.getABaseClass*() = overridingType and
+    override.getDeclaringType() = overridingType and
+    overridingType.getABaseClass+() = f.getDeclaringType()
+  }
+}

cpp/ql/src/semmle/code/cpp/exprs/Access.qll

@@ -18,7 +18,18 @@ abstract class Access extends Expr, NameQualifiableElement {
 }
 
 /**
- * A C/C++ enum constant access expression.
+ * A C/C++ `enum` constant access expression. For example the access to
+ * `MYENUMCONST1` in `myFunction` in the following code:
+ * ```
+ * enum MyEnum {
+ *   MYENUMCONST1,
+ *   MYENUMCONST2
+ * };
+ *
+ * void myFunction() {
+ *   MyEnum v = MYENUMCONST1;
+ * };
+ * ```
  */
 class EnumConstantAccess extends Access, @varaccess {
   override string getCanonicalQLClass() { result = "EnumConstantAccess" }
@@ -27,15 +38,23 @@ class EnumConstantAccess extends Access, @varaccess {
     exists(EnumConstant c | varbind(underlyingElement(this), unresolveElement(c)))
   }
 
-  /** Gets the accessed enum constant. */
+  /** Gets the accessed `enum` constant. */
   override EnumConstant getTarget() { varbind(underlyingElement(this), unresolveElement(result)) }
 
-  /** Gets a textual representation of this enum constant access. */
+  /** Gets a textual representation of this `enum` constant access. */
   override string toString() { result = this.getTarget().getName() }
 }
 
 /**
- * A C/C++ variable access expression.
+ * A C/C++ variable access expression. For example the accesses to
+ * `x` and `y` in `myFunction` in the following code:
+ * ```
+ * int x;
+ *
+ * void myFunction(int y) {
+ *   x = y;
+ * };
+ * ```
  */
 class VariableAccess extends Access, @varaccess {
   override string getCanonicalQLClass() { result = "VariableAccess" }
@@ -129,7 +148,18 @@ class VariableAccess extends Access, @varaccess {
 }
 
 /**
- * A C/C++ field access expression.
+ * A C/C++ field access expression. For example the accesses to
+ * `x` and `y` in `myMethod` in the following code:
+ * ```
+ * class MyClass {
+ * public:
+ *   void myMethod(MyClass &other) {
+ *     x = other.y;
+ *   }
+ *
+ *   int x, y;
+ * };
+ * ```
  */
 class FieldAccess extends VariableAccess {
   override string getCanonicalQLClass() { result = "FieldAccess" }
@@ -141,8 +171,23 @@ class FieldAccess extends VariableAccess {
 }
 
 /**
- * A field access of the form `obj->field`. The type of `obj` is a pointer,
- * so this is equivalent to `(*obj).field`.
+ * A field access whose qualifier is a pointer to a class, struct or union.
+ * These typically take the form `obj->field`. Another case is a field access
+ * with an implicit `this->` qualifier, which is often a `PointerFieldAccess`
+ * (but see also `ImplicitThisFieldAccess`).
+ *
+ * For example the accesses to `x` and `y` in `myMethod` in the following code
+ * are each a `PointerFieldAccess`:
+ * ```
+ * class MyClass {
+ * public:
+ *   void myMethod(MyClass *other) {
+ *       other->x = y;
+ *   }
+ *
+ *   int x, y;
+ * };
+ * ```
  */
 class PointerFieldAccess extends FieldAccess {
   override string getCanonicalQLClass() { result = "PointerFieldAccess" }
@@ -169,7 +214,18 @@ class DotFieldAccess extends FieldAccess {
 
 /**
  * A field access of the form `obj.field`, where the type of `obj` is a
- * reference to a class/struct/union.
+ * reference to a class/struct/union. For example the accesses to `y` in
+ * `myMethod` in the following code:
+ * ```
+ * class MyClass {
+ * public:
+ *   void myMethod(MyClass a, MyClass &b) {
+ *     a.x = b.y;
+ *   }
+ *
+ *   int x, y;
+ * };
+ * ```
  */
 class ReferenceFieldAccess extends DotFieldAccess {
   override string getCanonicalQLClass() { result = "ReferenceFieldAccess" }
@@ -179,7 +235,18 @@ class ReferenceFieldAccess extends DotFieldAccess {
 
 /**
  * A field access of the form `obj.field`, where the type of `obj` is a
- * class/struct/union (and not a reference).
+ * class/struct/union (and not a reference). For example the accesses to `x`
+ * in `myMethod` in the following code:
+ * ```
+ * class MyClass {
+ * public:
+ *   void myMethod(MyClass a, MyClass &b) {
+ *     a.x = b.y;
+ *   }
+ *
+ *   int x, y;
+ * };
+ * ```
  */
 class ValueFieldAccess extends DotFieldAccess {
   override string getCanonicalQLClass() { result = "ValueFieldAccess" }
@@ -198,25 +265,40 @@ private predicate referenceConversion(Conversion c) {
 /**
  * Holds if `e` is a reference expression (that is, it has a type of the
  * form `T&`), which is converted to a value. For example:
- *
  * ```
  * int myfcn(MyStruct &x) {
  *   return x.field;
  * }
  * ```
- *
  * In this example, the type of `x` is `MyStruct&`, but it gets implicitly
  * converted to `MyStruct` in the expression `x.field`.
  */
 private predicate exprHasReferenceConversion(Expr e) { referenceConversion(e.getConversion+()) }
 
 /**
- * A field access of a field of `this`. The access has no qualifier because
- * the use of `this` is implicit. For example, `field` is equivalent to
- * `this->field` if `field` is a member of `this`.
+ * A field access of a field of `this` which has no qualifier because
+ * the use of `this` is implicit. For example, in the following code the
+ * implicit call to the destructor of `A` has no qualifier because the
+ * use of `this` is implicit:
+ * ```
+ * class A {
+ * public:
+ *   ~A() {
+ *     // ...
+ *   }
+ * };
  *
+ * class B {
+ * public:
+ *   A a;
+ *
+ *   ~B() {
+ *     // Implicit call to the destructor of `A`.
+ *   }
+ * };
+ * ```
  * Note: the C++ front-end often automatically desugars `field` to
- * `this->field`, so most implicit accesses of `this->field` are instances
+ * `this->field`, so most accesses of `this->field` are instances
  * of `PointerFieldAccess` (with `ThisExpr` as the qualifier), not
  * `ImplicitThisFieldAccess`.
  */
@@ -250,7 +332,15 @@ class PointerToFieldLiteral extends ImplicitThisFieldAccess {
 }
 
 /**
- * A C/C++ function access expression.
+ * A C/C++ function access expression. For example the access to
+ * `myFunctionTarget` in `myFunction` in the following code:
+ * ```
+ * int myFunctionTarget(int);
+ *
+ * void myFunction() {
+ *   int (*myFunctionPointer)(int) = &myTarget;
+ * }
+ * ```
  */
 class FunctionAccess extends Access, @routineexpr {
   FunctionAccess() { not iscall(underlyingElement(this), _) }
@@ -269,7 +359,7 @@ class FunctionAccess extends Access, @routineexpr {
 }
 
 /**
- * An access to a parameter of a function signature for the purposes of a decltype.
+ * An access to a parameter of a function signature for the purposes of a `decltype`.
  *
  * For example, given the following code:
  * ```
@@ -279,7 +369,7 @@ class FunctionAccess extends Access, @routineexpr {
  *   }
  * ```
  * The return type of the function is a decltype, the expression of which contains
- * an add expression, which in turn has two ParamAccessForType children.
+ * an add expression, which in turn has two `ParamAccessForType` children.
  */
 class ParamAccessForType extends Expr, @param_ref {
   override string toString() { result = "param access" }
@@ -287,7 +377,22 @@ class ParamAccessForType extends Expr, @param_ref {
 
 /**
  * An access to a type.  This occurs in certain contexts where a built-in
- * works on types directly rather than variables, expressions etc.
+ * works on types directly rather than variables, expressions etc.  For
+ * example the reference to `MyClass` in `__is_pod` in the following code:
+ * ```
+ * class MyClass {
+ *   ...
+ * };
+ *
+ * void myFunction() {
+ *   if (__is_pod(MyClass))
+ *   {
+ *     ...
+ *   } else {
+ *     ...
+ *   }
+ * }
+ * ```
  */
 class TypeName extends Expr, @type_operand {
   override string getCanonicalQLClass() { result = "TypeName" }
@@ -296,9 +401,17 @@ class TypeName extends Expr, @type_operand {
 }
 
 /**
- * A C/C++ array access expression.
+ * A C/C++ array access expression. For example, the access to `as` in
+ * `myFunction` in the following code:
+ * ```
+ * int as[10];
  *
- * For calls to operator[], which look syntactically identical, see OverloadedArrayExpr.
+ * void myFunction() {
+ *   as[0]++;
+ * }
+ * ```
+ * For calls to `operator[]`, which look syntactically identical, see
+ * `OverloadedArrayExpr`.
  */
 class ArrayExpr extends Expr, @subscriptexpr {
   override string getCanonicalQLClass() { result = "ArrayExpr" }
@@ -306,14 +419,14 @@ class ArrayExpr extends Expr, @subscriptexpr {
   /**
    * Gets the array or pointer expression being subscripted.
    *
-   * This is arr in both arr[0] and 0[arr].
+   * This is `arr` in both `arr[0]` and `0[arr]`.
    */
   Expr getArrayBase() { result = this.getChild(0) }
 
   /**
    * Gets the expression giving the index into the array.
    *
-   * This is 0 in both arr[0] and 0[arr].
+   * This is `0` in both `arr[0]` and `0[arr]`.
    */
   Expr getArrayOffset() { result = this.getChild(1) }
 

cpp/ql/src/semmle/code/cpp/exprs/ArithmeticOperation.qll

@@ -32,6 +32,8 @@ class UnaryPlusExpr extends UnaryArithmeticOperation, @unaryplusexpr {
  */
 class ConjugationExpr extends UnaryArithmeticOperation, @conjugation {
   override string getOperator() { result = "~" }
+
+  override string getCanonicalQLClass() { result = "ConjugationExpr" }
 }
 
 /**
@@ -142,6 +144,8 @@ class PostfixDecrExpr extends DecrementOperation, PostfixCrementOperation, @post
  */
 class RealPartExpr extends UnaryArithmeticOperation, @realpartexpr {
   override string getOperator() { result = "__real" }
+
+  override string getCanonicalQLClass() { result = "RealPartExpr" }
 }
 
 /**
@@ -149,6 +153,8 @@ class RealPartExpr extends UnaryArithmeticOperation, @realpartexpr {
  */
 class ImaginaryPartExpr extends UnaryArithmeticOperation, @imagpartexpr {
   override string getOperator() { result = "__imag" }
+
+  override string getCanonicalQLClass() { result = "ImaginaryPartExpr" }
 }
 
 /**
@@ -217,6 +223,8 @@ class RemExpr extends BinaryArithmeticOperation, @remexpr {
 class ImaginaryMulExpr extends BinaryArithmeticOperation, @jmulexpr {
   override string getOperator() { result = "*" }
 
+  override string getCanonicalQLClass() { result = "ImaginaryMulExpr" }
+
   override int getPrecedence() { result = 13 }
 }
 
@@ -226,6 +234,8 @@ class ImaginaryMulExpr extends BinaryArithmeticOperation, @jmulexpr {
 class ImaginaryDivExpr extends BinaryArithmeticOperation, @jdivexpr {
   override string getOperator() { result = "/" }
 
+  override string getCanonicalQLClass() { result = "ImaginaryDivExpr" }
+
   override int getPrecedence() { result = 13 }
 }
 
@@ -235,6 +245,8 @@ class ImaginaryDivExpr extends BinaryArithmeticOperation, @jdivexpr {
 class RealImaginaryAddExpr extends BinaryArithmeticOperation, @fjaddexpr {
   override string getOperator() { result = "+" }
 
+  override string getCanonicalQLClass() { result = "RealImaginaryAddExpr" }
+
   override int getPrecedence() { result = 12 }
 }
 
@@ -244,6 +256,8 @@ class RealImaginaryAddExpr extends BinaryArithmeticOperation, @fjaddexpr {
 class ImaginaryRealAddExpr extends BinaryArithmeticOperation, @jfaddexpr {
   override string getOperator() { result = "+" }
 
+  override string getCanonicalQLClass() { result = "ImaginaryRealAddExpr" }
+
   override int getPrecedence() { result = 12 }
 }
 
@@ -253,6 +267,8 @@ class ImaginaryRealAddExpr extends BinaryArithmeticOperation, @jfaddexpr {
 class RealImaginarySubExpr extends BinaryArithmeticOperation, @fjsubexpr {
   override string getOperator() { result = "-" }
 
+  override string getCanonicalQLClass() { result = "RealImaginarySubExpr" }
+
   override int getPrecedence() { result = 12 }
 }
 
@@ -262,6 +278,8 @@ class RealImaginarySubExpr extends BinaryArithmeticOperation, @fjsubexpr {
 class ImaginaryRealSubExpr extends BinaryArithmeticOperation, @jfsubexpr {
   override string getOperator() { result = "-" }
 
+  override string getCanonicalQLClass() { result = "ImaginaryRealSubExpr" }
+
   override int getPrecedence() { result = 12 }
 }
 
@@ -270,6 +288,8 @@ class ImaginaryRealSubExpr extends BinaryArithmeticOperation, @jfsubexpr {
  */
 class MinExpr extends BinaryArithmeticOperation, @minexpr {
   override string getOperator() { result = "<?" }
+
+  override string getCanonicalQLClass() { result = "MinExpr" }
 }
 
 /**
@@ -277,6 +297,8 @@ class MinExpr extends BinaryArithmeticOperation, @minexpr {
  */
 class MaxExpr extends BinaryArithmeticOperation, @maxexpr {
   override string getOperator() { result = ">?" }
+
+  override string getCanonicalQLClass() { result = "MaxExpr" }
 }
 
 /**

cpp/ql/src/semmle/code/cpp/exprs/BuiltInOperations.qll

@@ -519,3 +519,18 @@ class BuiltInChooseExpr extends BuiltInOperation, @builtinchooseexpr {
 class VectorFillOperation extends UnaryOperation, @vec_fill {
   override string getOperator() { result = "(vector fill)" }
 }
+
+/**
+ * The GNU `__builtin_complex` operation.
+ */
+class BuiltInComplexOperation extends BuiltInOperation, @builtincomplex {
+  override string toString() { result = "__builtin_complex" }
+
+  override string getCanonicalQLClass() { result = "BuiltInComplexOperation" }
+
+  /** Gets the operand corresponding to the real part of the complex number. */
+  Expr getRealOperand() { this.hasChild(result, 0) }
+
+  /** Gets the operand corresponding to the imaginary part of the complex number. */
+  Expr getImaginaryOperand() { this.hasChild(result, 1) }
+}

cpp/ql/src/semmle/code/cpp/exprs/Call.qll

@@ -139,17 +139,29 @@ class FunctionCall extends Call, @funbindexpr {
   override string getCanonicalQLClass() { result = "FunctionCall" }
 
   /** Gets an explicit template argument for this call. */
-  Type getAnExplicitTemplateArgument() { result = getExplicitTemplateArgument(_) }
+  Locatable getAnExplicitTemplateArgument() { result = getExplicitTemplateArgument(_) }
+
+  /** Gets an explicit template argument value for this call. */
+  Locatable getAnExplicitTemplateArgumentKind() { result = getExplicitTemplateArgumentKind(_) }
 
   /** Gets a template argument for this call. */
-  Type getATemplateArgument() { result = getTarget().getATemplateArgument() }
+  Locatable getATemplateArgument() { result = getTarget().getATemplateArgument() }
+
+  /** Gets a template argument value for this call. */
+  Locatable getATemplateArgumentKind() { result = getTarget().getATemplateArgumentKind() }
 
   /** Gets the nth explicit template argument for this call. */
-  Type getExplicitTemplateArgument(int n) {
+  Locatable getExplicitTemplateArgument(int n) {
     n < getNumberOfExplicitTemplateArguments() and
     result = getTemplateArgument(n)
   }
 
+  /** Gets the nth explicit template argument value for this call. */
+  Locatable getExplicitTemplateArgumentKind(int n) {
+    n < getNumberOfExplicitTemplateArguments() and
+    result = getTemplateArgumentKind(n)
+  }
+
   /** Gets the number of explicit template arguments for this call. */
   int getNumberOfExplicitTemplateArguments() {
     if numtemplatearguments(underlyingElement(this), _)
@@ -161,7 +173,10 @@ class FunctionCall extends Call, @funbindexpr {
   int getNumberOfTemplateArguments() { result = count(int i | exists(getTemplateArgument(i))) }
 
   /** Gets the nth template argument for this call (indexed from 0). */
-  Type getTemplateArgument(int n) { result = getTarget().getTemplateArgument(n) }
+  Locatable getTemplateArgument(int n) { result = getTarget().getTemplateArgument(n) }
+
+  /** Gets the nth template argument value for this call (indexed from 0). */
+  Locatable getTemplateArgumentKind(int n) { result = getTarget().getTemplateArgumentKind(n) }
 
   /** Holds if any template arguments for this call are implicit / deduced. */
   predicate hasImplicitTemplateArguments() {

cpp/ql/src/semmle/code/cpp/exprs/Expr.qll

@@ -540,6 +540,13 @@ class ErrorExpr extends Expr, @errorexpr {
  */
 class AssumeExpr extends Expr, @assume {
   override string toString() { result = "__assume(...)" }
+
+  override string getCanonicalQLClass() { result = "AssumeExpr" }
+
+  /**
+   * Gets the operand of the `__assume` expressions.
+   */
+  Expr getOperand() { this.hasChild(result, 0) }
 }
 
 /**

cpp/ql/src/semmle/code/cpp/ir/dataflow/DefaultTaintTracking.qll

@@ -4,25 +4,17 @@ private import semmle.code.cpp.ir.dataflow.DataFlow
 private import semmle.code.cpp.ir.IR
 
 /**
- * A predictable expression is one where an external user can predict
+ * A predictable instruction is one where an external user can predict
  * the value. For example, a literal in the source code is considered
  * predictable.
  */
-// TODO: Change to use Instruction instead of Expr. Naive attempt breaks
-// TaintedAllocationSize qltest.
-private predicate predictable(Expr expr) {
-  expr instanceof Literal
-  or
-  exists(BinaryOperation binop | binop = expr |
-    predictable(binop.getLeftOperand()) and predictable(binop.getRightOperand())
-  )
-  or
-  exists(UnaryOperation unop | unop = expr | predictable(unop.getOperand()))
-}
-
-// TODO: remove when `predictable` has an `Instruction` parameter instead of `Expr`.
 private predicate predictableInstruction(Instruction instr) {
-  predictable(DataFlow::instructionNode(instr).asExpr())
+  instr instanceof ConstantInstruction
+  or
+  instr instanceof StringConstantInstruction
+  or
+  // This could be a conversion on a string literal
+  predictableInstruction(instr.(UnaryInstruction).getUnary())
 }
 
 private class DefaultTaintTrackingCfg extends DataFlow::Configuration {
@@ -45,7 +37,7 @@ private class DefaultTaintTrackingCfg extends DataFlow::Configuration {
 }
 
 private predicate accessesVariable(CopyInstruction copy, Variable var) {
-  exists(VariableAddressInstruction va | va.getVariable().getAST() = var |
+  exists(VariableAddressInstruction va | va.getASTVariable() = var |
     copy.(StoreInstruction).getDestinationAddress() = va
     or
     copy.(LoadInstruction).getSourceAddress() = va

cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowImpl.qll

@@ -905,30 +905,35 @@ private predicate localFlowExit(Node node, Configuration config) {
  */
 pragma[nomagic]
 private predicate localFlowStepPlus(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext cc
 ) {
-  localFlowEntry(node1, config) and
+  not isUnreachableInCall(node2, cc.(LocalCallContextSpecificCall).getCall()) and
   (
-    localFlowStep(node1, node2, config) and preservesValue = true
+    localFlowEntry(node1, config) and
+    (
+      localFlowStep(node1, node2, config) and preservesValue = true
+      or
+      additionalLocalFlowStep(node1, node2, config) and preservesValue = false
+    ) and
+    node1 != node2 and
+    cc.relevantFor(node1.getEnclosingCallable()) and
+    not isUnreachableInCall(node1, cc.(LocalCallContextSpecificCall).getCall()) and
+    nodeCand(node2, unbind(config))
     or
-    additionalLocalFlowStep(node1, node2, config) and preservesValue = false
-  ) and
-  node1 != node2 and
-  nodeCand(node2, unbind(config))
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, preservesValue, config) and
-    localFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    nodeCand(node2, unbind(config))
-  )
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, _, config) and
-    additionalLocalFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    preservesValue = false and
-    nodeCand(node2, unbind(config))
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, preservesValue, config, cc) and
+      localFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      nodeCand(node2, unbind(config))
+    )
+    or
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, _, config, cc) and
+      additionalLocalFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      preservesValue = false and
+      nodeCand(node2, unbind(config))
+    )
   )
 }
 
@@ -936,11 +941,11 @@ private predicate localFlowStepPlus(
  * Holds if `node1` can step to `node2` in one or more local steps and this
  * path can occur as a maximal subsequence of local steps in a dataflow path.
  */
-pragma[noinline]
+pragma[nomagic]
 private predicate localFlowBigStep(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext callContext
 ) {
-  localFlowStepPlus(node1, node2, preservesValue, config) and
+  localFlowStepPlus(node1, node2, preservesValue, config, callContext) and
   localFlowExit(node2, config)
 }
 
@@ -1000,7 +1005,7 @@ private class AccessPathFrontNilNode extends Node {
     (
       any(Configuration c).isSource(this)
       or
-      localFlowBigStep(_, this, false, _)
+      localFlowBigStep(_, this, false, _, _)
       or
       additionalJumpStep(_, this, _)
     )
@@ -1023,12 +1028,12 @@ private predicate flowCandFwd0(Node node, boolean fromArg, AccessPathFront apf,
   (
     exists(Node mid |
       flowCandFwd(mid, fromArg, apf, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathFrontNil nil |
       flowCandFwd(mid, fromArg, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       apf = node.(AccessPathFrontNilNode).getApf()
     )
     or
@@ -1122,13 +1127,13 @@ private predicate flowCand0(Node node, boolean toReturn, AccessPathFront apf, Co
   apf instanceof AccessPathFrontNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flowCand(mid, toReturn, apf, config)
   )
   or
   exists(Node mid, AccessPathFrontNil nil |
     flowCandFwd(node, _, apf, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flowCand(mid, toReturn, nil, config) and
     apf instanceof AccessPathFrontNil
   )
@@ -1261,7 +1266,7 @@ abstract private class AccessPath extends TAccessPath {
 
 private class AccessPathNil extends AccessPath, TNil {
   override string toString() {
-    exists(DataFlowType t | this = TNil(t) | result = concat(" : " + ppReprType(t)))
+    exists(DataFlowType t | this = TNil(t) | result = concat(": " + ppReprType(t)))
   }
 
   override AccessPathFront getFront() {
@@ -1277,7 +1282,7 @@ private class AccessPathConsNil extends AccessPathCons, TConsNil {
   override string toString() {
     exists(Content f, DataFlowType t | this = TConsNil(f, t) |
       // The `concat` becomes "" if `ppReprType` has no result.
-      result = f.toString() + concat(" : " + ppReprType(t))
+      result = "[" + f.toString() + "]" + concat(" : " + ppReprType(t))
     )
   }
 
@@ -1294,8 +1299,8 @@ private class AccessPathConsCons extends AccessPathCons, TConsCons {
   override string toString() {
     exists(Content f1, Content f2, int len | this = TConsCons(f1, f2, len) |
       if len = 2
-      then result = f1.toString() + ", " + f2.toString()
-      else result = f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")"
+      then result = "[" + f1.toString() + ", " + f2.toString() + "]"
+      else result = "[" + f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")]"
     )
   }
 
@@ -1363,12 +1368,12 @@ private predicate flowFwd0(
   (
     exists(Node mid |
       flowFwd(mid, fromArg, apf, ap, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathNil nil |
       flowFwd(mid, fromArg, _, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       ap = node.(AccessPathNilNode).getAp() and
       apf = ap.(AccessPathNil).getFront()
     )
@@ -1472,13 +1477,13 @@ private predicate flow0(Node node, boolean toReturn, AccessPath ap, Configuratio
   ap instanceof AccessPathNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flow(mid, toReturn, ap, config)
   )
   or
   exists(Node mid, AccessPathNil nil |
     flowFwd(node, _, _, ap, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flow(mid, toReturn, nil, config) and
     ap instanceof AccessPathNil
   )
@@ -1626,7 +1631,7 @@ abstract class PathNode extends TPathNode {
     this instanceof PathNodeSink and result = ""
     or
     exists(string s | s = this.(PathNodeMid).getAp().toString() |
-      if s = "" then result = "" else result = " [" + s + "]"
+      if s = "" then result = "" else result = " " + s
     )
   }
 
@@ -1729,14 +1734,20 @@ private class PathNodeSink extends PathNode, TPathNodeSink {
  * a callable is recorded by `cc`.
  */
 private predicate pathStep(PathNodeMid mid, Node node, CallContext cc, AccessPath ap) {
-  localFlowBigStep(mid.getNode(), node, true, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  ap = mid.getAp()
-  or
-  localFlowBigStep(mid.getNode(), node, false, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  mid.getAp() instanceof AccessPathNil and
-  ap = node.(AccessPathNilNode).getAp()
+  exists(LocalCallContext localCC, AccessPath ap0, Node midnode, Configuration conf |
+    midnode = mid.getNode() and
+    conf = mid.getConfiguration() and
+    cc = mid.getCallContext() and
+    localCC = getLocalCallContext(cc, midnode.getEnclosingCallable()) and
+    ap0 = mid.getAp()
+  |
+    localFlowBigStep(midnode, node, true, conf, localCC) and
+    ap = ap0
+    or
+    localFlowBigStep(midnode, node, false, conf, localCC) and
+    ap0 instanceof AccessPathNil and
+    ap = node.(AccessPathNilNode).getAp()
+  )
   or
   jumpStep(mid.getNode(), node, mid.getConfiguration()) and
   cc instanceof CallContextAny and
@@ -1880,7 +1891,7 @@ private predicate pathIntoCallable(
     pathIntoCallable0(mid, callable, i, outercc, call, emptyAp) and
     p.isParameterOf(callable, i)
   |
-    if reducedViableImplInCallContext(_, callable, call)
+    if recordDataFlowCallSite(call, callable)
     then innercc = TSpecificCall(call, i, emptyAp)
     else innercc = TSomeCall(p, emptyAp)
   )
@@ -2071,7 +2082,7 @@ private module FlowExploration {
 
   private class PartialAccessPathNil extends PartialAccessPath, TPartialNil {
     override string toString() {
-      exists(DataFlowType t | this = TPartialNil(t) | result = concat(" : " + ppReprType(t)))
+      exists(DataFlowType t | this = TPartialNil(t) | result = concat(": " + ppReprType(t)))
     }
 
     override AccessPathFront getFront() {
@@ -2083,8 +2094,8 @@ private module FlowExploration {
     override string toString() {
       exists(Content f, int len | this = TPartialCons(f, len) |
         if len = 1
-        then result = f.toString()
-        else result = f.toString() + ", ... (" + len.toString() + ")"
+        then result = "[" + f.toString() + "]"
+        else result = "[" + f.toString() + ", ... (" + len.toString() + ")]"
       )
     }
 
@@ -2161,7 +2172,7 @@ private module FlowExploration {
 
     private string ppAp() {
       exists(string s | s = this.(PartialPathNodePriv).getAp().toString() |
-        if s = "" then result = "" else result = " [" + s + "]"
+        if s = "" then result = "" else result = " " + s
       )
     }
 
@@ -2205,16 +2216,19 @@ private module FlowExploration {
   private predicate partialPathStep(
     PartialPathNodePriv mid, Node node, CallContext cc, PartialAccessPath ap, Configuration config
   ) {
-    localFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    ap = mid.getAp() and
-    config = mid.getConfiguration()
-    or
-    additionalLocalFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    mid.getAp() instanceof PartialAccessPathNil and
-    ap = TPartialNil(getErasedRepr(node.getType())) and
-    config = mid.getConfiguration()
+    not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall()) and
+    (
+      localFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      ap = mid.getAp() and
+      config = mid.getConfiguration()
+      or
+      additionalLocalFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      mid.getAp() instanceof PartialAccessPathNil and
+      ap = TPartialNil(getErasedRepr(node.getType())) and
+      config = mid.getConfiguration()
+    )
     or
     jumpStep(mid.getNode(), node, config) and
     cc instanceof CallContextAny and
@@ -2378,7 +2392,7 @@ private module FlowExploration {
       partialPathIntoCallable0(mid, callable, i, outercc, call, emptyAp, ap, config) and
       p.isParameterOf(callable, i)
     |
-      if reducedViableImplInCallContext(_, callable, call)
+      if recordDataFlowCallSite(call, callable)
       then innercc = TSpecificCall(call, i, emptyAp)
       else innercc = TSomeCall(p, emptyAp)
     )

cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowImpl2.qll

@@ -905,30 +905,35 @@ private predicate localFlowExit(Node node, Configuration config) {
  */
 pragma[nomagic]
 private predicate localFlowStepPlus(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext cc
 ) {
-  localFlowEntry(node1, config) and
+  not isUnreachableInCall(node2, cc.(LocalCallContextSpecificCall).getCall()) and
   (
-    localFlowStep(node1, node2, config) and preservesValue = true
+    localFlowEntry(node1, config) and
+    (
+      localFlowStep(node1, node2, config) and preservesValue = true
+      or
+      additionalLocalFlowStep(node1, node2, config) and preservesValue = false
+    ) and
+    node1 != node2 and
+    cc.relevantFor(node1.getEnclosingCallable()) and
+    not isUnreachableInCall(node1, cc.(LocalCallContextSpecificCall).getCall()) and
+    nodeCand(node2, unbind(config))
     or
-    additionalLocalFlowStep(node1, node2, config) and preservesValue = false
-  ) and
-  node1 != node2 and
-  nodeCand(node2, unbind(config))
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, preservesValue, config) and
-    localFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    nodeCand(node2, unbind(config))
-  )
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, _, config) and
-    additionalLocalFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    preservesValue = false and
-    nodeCand(node2, unbind(config))
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, preservesValue, config, cc) and
+      localFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      nodeCand(node2, unbind(config))
+    )
+    or
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, _, config, cc) and
+      additionalLocalFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      preservesValue = false and
+      nodeCand(node2, unbind(config))
+    )
   )
 }
 
@@ -936,11 +941,11 @@ private predicate localFlowStepPlus(
  * Holds if `node1` can step to `node2` in one or more local steps and this
  * path can occur as a maximal subsequence of local steps in a dataflow path.
  */
-pragma[noinline]
+pragma[nomagic]
 private predicate localFlowBigStep(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext callContext
 ) {
-  localFlowStepPlus(node1, node2, preservesValue, config) and
+  localFlowStepPlus(node1, node2, preservesValue, config, callContext) and
   localFlowExit(node2, config)
 }
 
@@ -1000,7 +1005,7 @@ private class AccessPathFrontNilNode extends Node {
     (
       any(Configuration c).isSource(this)
       or
-      localFlowBigStep(_, this, false, _)
+      localFlowBigStep(_, this, false, _, _)
       or
       additionalJumpStep(_, this, _)
     )
@@ -1023,12 +1028,12 @@ private predicate flowCandFwd0(Node node, boolean fromArg, AccessPathFront apf,
   (
     exists(Node mid |
       flowCandFwd(mid, fromArg, apf, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathFrontNil nil |
       flowCandFwd(mid, fromArg, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       apf = node.(AccessPathFrontNilNode).getApf()
     )
     or
@@ -1122,13 +1127,13 @@ private predicate flowCand0(Node node, boolean toReturn, AccessPathFront apf, Co
   apf instanceof AccessPathFrontNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flowCand(mid, toReturn, apf, config)
   )
   or
   exists(Node mid, AccessPathFrontNil nil |
     flowCandFwd(node, _, apf, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flowCand(mid, toReturn, nil, config) and
     apf instanceof AccessPathFrontNil
   )
@@ -1261,7 +1266,7 @@ abstract private class AccessPath extends TAccessPath {
 
 private class AccessPathNil extends AccessPath, TNil {
   override string toString() {
-    exists(DataFlowType t | this = TNil(t) | result = concat(" : " + ppReprType(t)))
+    exists(DataFlowType t | this = TNil(t) | result = concat(": " + ppReprType(t)))
   }
 
   override AccessPathFront getFront() {
@@ -1277,7 +1282,7 @@ private class AccessPathConsNil extends AccessPathCons, TConsNil {
   override string toString() {
     exists(Content f, DataFlowType t | this = TConsNil(f, t) |
       // The `concat` becomes "" if `ppReprType` has no result.
-      result = f.toString() + concat(" : " + ppReprType(t))
+      result = "[" + f.toString() + "]" + concat(" : " + ppReprType(t))
     )
   }
 
@@ -1294,8 +1299,8 @@ private class AccessPathConsCons extends AccessPathCons, TConsCons {
   override string toString() {
     exists(Content f1, Content f2, int len | this = TConsCons(f1, f2, len) |
       if len = 2
-      then result = f1.toString() + ", " + f2.toString()
-      else result = f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")"
+      then result = "[" + f1.toString() + ", " + f2.toString() + "]"
+      else result = "[" + f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")]"
     )
   }
 
@@ -1363,12 +1368,12 @@ private predicate flowFwd0(
   (
     exists(Node mid |
       flowFwd(mid, fromArg, apf, ap, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathNil nil |
       flowFwd(mid, fromArg, _, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       ap = node.(AccessPathNilNode).getAp() and
       apf = ap.(AccessPathNil).getFront()
     )
@@ -1472,13 +1477,13 @@ private predicate flow0(Node node, boolean toReturn, AccessPath ap, Configuratio
   ap instanceof AccessPathNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flow(mid, toReturn, ap, config)
   )
   or
   exists(Node mid, AccessPathNil nil |
     flowFwd(node, _, _, ap, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flow(mid, toReturn, nil, config) and
     ap instanceof AccessPathNil
   )
@@ -1626,7 +1631,7 @@ abstract class PathNode extends TPathNode {
     this instanceof PathNodeSink and result = ""
     or
     exists(string s | s = this.(PathNodeMid).getAp().toString() |
-      if s = "" then result = "" else result = " [" + s + "]"
+      if s = "" then result = "" else result = " " + s
     )
   }
 
@@ -1729,14 +1734,20 @@ private class PathNodeSink extends PathNode, TPathNodeSink {
  * a callable is recorded by `cc`.
  */
 private predicate pathStep(PathNodeMid mid, Node node, CallContext cc, AccessPath ap) {
-  localFlowBigStep(mid.getNode(), node, true, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  ap = mid.getAp()
-  or
-  localFlowBigStep(mid.getNode(), node, false, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  mid.getAp() instanceof AccessPathNil and
-  ap = node.(AccessPathNilNode).getAp()
+  exists(LocalCallContext localCC, AccessPath ap0, Node midnode, Configuration conf |
+    midnode = mid.getNode() and
+    conf = mid.getConfiguration() and
+    cc = mid.getCallContext() and
+    localCC = getLocalCallContext(cc, midnode.getEnclosingCallable()) and
+    ap0 = mid.getAp()
+  |
+    localFlowBigStep(midnode, node, true, conf, localCC) and
+    ap = ap0
+    or
+    localFlowBigStep(midnode, node, false, conf, localCC) and
+    ap0 instanceof AccessPathNil and
+    ap = node.(AccessPathNilNode).getAp()
+  )
   or
   jumpStep(mid.getNode(), node, mid.getConfiguration()) and
   cc instanceof CallContextAny and
@@ -1880,7 +1891,7 @@ private predicate pathIntoCallable(
     pathIntoCallable0(mid, callable, i, outercc, call, emptyAp) and
     p.isParameterOf(callable, i)
   |
-    if reducedViableImplInCallContext(_, callable, call)
+    if recordDataFlowCallSite(call, callable)
     then innercc = TSpecificCall(call, i, emptyAp)
     else innercc = TSomeCall(p, emptyAp)
   )
@@ -2071,7 +2082,7 @@ private module FlowExploration {
 
   private class PartialAccessPathNil extends PartialAccessPath, TPartialNil {
     override string toString() {
-      exists(DataFlowType t | this = TPartialNil(t) | result = concat(" : " + ppReprType(t)))
+      exists(DataFlowType t | this = TPartialNil(t) | result = concat(": " + ppReprType(t)))
     }
 
     override AccessPathFront getFront() {
@@ -2083,8 +2094,8 @@ private module FlowExploration {
     override string toString() {
       exists(Content f, int len | this = TPartialCons(f, len) |
         if len = 1
-        then result = f.toString()
-        else result = f.toString() + ", ... (" + len.toString() + ")"
+        then result = "[" + f.toString() + "]"
+        else result = "[" + f.toString() + ", ... (" + len.toString() + ")]"
       )
     }
 
@@ -2161,7 +2172,7 @@ private module FlowExploration {
 
     private string ppAp() {
       exists(string s | s = this.(PartialPathNodePriv).getAp().toString() |
-        if s = "" then result = "" else result = " [" + s + "]"
+        if s = "" then result = "" else result = " " + s
       )
     }
 
@@ -2205,16 +2216,19 @@ private module FlowExploration {
   private predicate partialPathStep(
     PartialPathNodePriv mid, Node node, CallContext cc, PartialAccessPath ap, Configuration config
   ) {
-    localFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    ap = mid.getAp() and
-    config = mid.getConfiguration()
-    or
-    additionalLocalFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    mid.getAp() instanceof PartialAccessPathNil and
-    ap = TPartialNil(getErasedRepr(node.getType())) and
-    config = mid.getConfiguration()
+    not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall()) and
+    (
+      localFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      ap = mid.getAp() and
+      config = mid.getConfiguration()
+      or
+      additionalLocalFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      mid.getAp() instanceof PartialAccessPathNil and
+      ap = TPartialNil(getErasedRepr(node.getType())) and
+      config = mid.getConfiguration()
+    )
     or
     jumpStep(mid.getNode(), node, config) and
     cc instanceof CallContextAny and
@@ -2378,7 +2392,7 @@ private module FlowExploration {
       partialPathIntoCallable0(mid, callable, i, outercc, call, emptyAp, ap, config) and
       p.isParameterOf(callable, i)
     |
-      if reducedViableImplInCallContext(_, callable, call)
+      if recordDataFlowCallSite(call, callable)
       then innercc = TSpecificCall(call, i, emptyAp)
       else innercc = TSomeCall(p, emptyAp)
     )

cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowImpl3.qll

@@ -905,30 +905,35 @@ private predicate localFlowExit(Node node, Configuration config) {
  */
 pragma[nomagic]
 private predicate localFlowStepPlus(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext cc
 ) {
-  localFlowEntry(node1, config) and
+  not isUnreachableInCall(node2, cc.(LocalCallContextSpecificCall).getCall()) and
   (
-    localFlowStep(node1, node2, config) and preservesValue = true
+    localFlowEntry(node1, config) and
+    (
+      localFlowStep(node1, node2, config) and preservesValue = true
+      or
+      additionalLocalFlowStep(node1, node2, config) and preservesValue = false
+    ) and
+    node1 != node2 and
+    cc.relevantFor(node1.getEnclosingCallable()) and
+    not isUnreachableInCall(node1, cc.(LocalCallContextSpecificCall).getCall()) and
+    nodeCand(node2, unbind(config))
     or
-    additionalLocalFlowStep(node1, node2, config) and preservesValue = false
-  ) and
-  node1 != node2 and
-  nodeCand(node2, unbind(config))
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, preservesValue, config) and
-    localFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    nodeCand(node2, unbind(config))
-  )
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, _, config) and
-    additionalLocalFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    preservesValue = false and
-    nodeCand(node2, unbind(config))
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, preservesValue, config, cc) and
+      localFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      nodeCand(node2, unbind(config))
+    )
+    or
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, _, config, cc) and
+      additionalLocalFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      preservesValue = false and
+      nodeCand(node2, unbind(config))
+    )
   )
 }
 
@@ -936,11 +941,11 @@ private predicate localFlowStepPlus(
  * Holds if `node1` can step to `node2` in one or more local steps and this
  * path can occur as a maximal subsequence of local steps in a dataflow path.
  */
-pragma[noinline]
+pragma[nomagic]
 private predicate localFlowBigStep(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext callContext
 ) {
-  localFlowStepPlus(node1, node2, preservesValue, config) and
+  localFlowStepPlus(node1, node2, preservesValue, config, callContext) and
   localFlowExit(node2, config)
 }
 
@@ -1000,7 +1005,7 @@ private class AccessPathFrontNilNode extends Node {
     (
       any(Configuration c).isSource(this)
       or
-      localFlowBigStep(_, this, false, _)
+      localFlowBigStep(_, this, false, _, _)
       or
       additionalJumpStep(_, this, _)
     )
@@ -1023,12 +1028,12 @@ private predicate flowCandFwd0(Node node, boolean fromArg, AccessPathFront apf,
   (
     exists(Node mid |
       flowCandFwd(mid, fromArg, apf, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathFrontNil nil |
       flowCandFwd(mid, fromArg, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       apf = node.(AccessPathFrontNilNode).getApf()
     )
     or
@@ -1122,13 +1127,13 @@ private predicate flowCand0(Node node, boolean toReturn, AccessPathFront apf, Co
   apf instanceof AccessPathFrontNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flowCand(mid, toReturn, apf, config)
   )
   or
   exists(Node mid, AccessPathFrontNil nil |
     flowCandFwd(node, _, apf, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flowCand(mid, toReturn, nil, config) and
     apf instanceof AccessPathFrontNil
   )
@@ -1261,7 +1266,7 @@ abstract private class AccessPath extends TAccessPath {
 
 private class AccessPathNil extends AccessPath, TNil {
   override string toString() {
-    exists(DataFlowType t | this = TNil(t) | result = concat(" : " + ppReprType(t)))
+    exists(DataFlowType t | this = TNil(t) | result = concat(": " + ppReprType(t)))
   }
 
   override AccessPathFront getFront() {
@@ -1277,7 +1282,7 @@ private class AccessPathConsNil extends AccessPathCons, TConsNil {
   override string toString() {
     exists(Content f, DataFlowType t | this = TConsNil(f, t) |
       // The `concat` becomes "" if `ppReprType` has no result.
-      result = f.toString() + concat(" : " + ppReprType(t))
+      result = "[" + f.toString() + "]" + concat(" : " + ppReprType(t))
     )
   }
 
@@ -1294,8 +1299,8 @@ private class AccessPathConsCons extends AccessPathCons, TConsCons {
   override string toString() {
     exists(Content f1, Content f2, int len | this = TConsCons(f1, f2, len) |
       if len = 2
-      then result = f1.toString() + ", " + f2.toString()
-      else result = f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")"
+      then result = "[" + f1.toString() + ", " + f2.toString() + "]"
+      else result = "[" + f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")]"
     )
   }
 
@@ -1363,12 +1368,12 @@ private predicate flowFwd0(
   (
     exists(Node mid |
       flowFwd(mid, fromArg, apf, ap, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathNil nil |
       flowFwd(mid, fromArg, _, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       ap = node.(AccessPathNilNode).getAp() and
       apf = ap.(AccessPathNil).getFront()
     )
@@ -1472,13 +1477,13 @@ private predicate flow0(Node node, boolean toReturn, AccessPath ap, Configuratio
   ap instanceof AccessPathNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flow(mid, toReturn, ap, config)
   )
   or
   exists(Node mid, AccessPathNil nil |
     flowFwd(node, _, _, ap, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flow(mid, toReturn, nil, config) and
     ap instanceof AccessPathNil
   )
@@ -1626,7 +1631,7 @@ abstract class PathNode extends TPathNode {
     this instanceof PathNodeSink and result = ""
     or
     exists(string s | s = this.(PathNodeMid).getAp().toString() |
-      if s = "" then result = "" else result = " [" + s + "]"
+      if s = "" then result = "" else result = " " + s
     )
   }
 
@@ -1729,14 +1734,20 @@ private class PathNodeSink extends PathNode, TPathNodeSink {
  * a callable is recorded by `cc`.
  */
 private predicate pathStep(PathNodeMid mid, Node node, CallContext cc, AccessPath ap) {
-  localFlowBigStep(mid.getNode(), node, true, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  ap = mid.getAp()
-  or
-  localFlowBigStep(mid.getNode(), node, false, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  mid.getAp() instanceof AccessPathNil and
-  ap = node.(AccessPathNilNode).getAp()
+  exists(LocalCallContext localCC, AccessPath ap0, Node midnode, Configuration conf |
+    midnode = mid.getNode() and
+    conf = mid.getConfiguration() and
+    cc = mid.getCallContext() and
+    localCC = getLocalCallContext(cc, midnode.getEnclosingCallable()) and
+    ap0 = mid.getAp()
+  |
+    localFlowBigStep(midnode, node, true, conf, localCC) and
+    ap = ap0
+    or
+    localFlowBigStep(midnode, node, false, conf, localCC) and
+    ap0 instanceof AccessPathNil and
+    ap = node.(AccessPathNilNode).getAp()
+  )
   or
   jumpStep(mid.getNode(), node, mid.getConfiguration()) and
   cc instanceof CallContextAny and
@@ -1880,7 +1891,7 @@ private predicate pathIntoCallable(
     pathIntoCallable0(mid, callable, i, outercc, call, emptyAp) and
     p.isParameterOf(callable, i)
   |
-    if reducedViableImplInCallContext(_, callable, call)
+    if recordDataFlowCallSite(call, callable)
     then innercc = TSpecificCall(call, i, emptyAp)
     else innercc = TSomeCall(p, emptyAp)
   )
@@ -2071,7 +2082,7 @@ private module FlowExploration {
 
   private class PartialAccessPathNil extends PartialAccessPath, TPartialNil {
     override string toString() {
-      exists(DataFlowType t | this = TPartialNil(t) | result = concat(" : " + ppReprType(t)))
+      exists(DataFlowType t | this = TPartialNil(t) | result = concat(": " + ppReprType(t)))
     }
 
     override AccessPathFront getFront() {
@@ -2083,8 +2094,8 @@ private module FlowExploration {
     override string toString() {
       exists(Content f, int len | this = TPartialCons(f, len) |
         if len = 1
-        then result = f.toString()
-        else result = f.toString() + ", ... (" + len.toString() + ")"
+        then result = "[" + f.toString() + "]"
+        else result = "[" + f.toString() + ", ... (" + len.toString() + ")]"
       )
     }
 
@@ -2161,7 +2172,7 @@ private module FlowExploration {
 
     private string ppAp() {
       exists(string s | s = this.(PartialPathNodePriv).getAp().toString() |
-        if s = "" then result = "" else result = " [" + s + "]"
+        if s = "" then result = "" else result = " " + s
       )
     }
 
@@ -2205,16 +2216,19 @@ private module FlowExploration {
   private predicate partialPathStep(
     PartialPathNodePriv mid, Node node, CallContext cc, PartialAccessPath ap, Configuration config
   ) {
-    localFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    ap = mid.getAp() and
-    config = mid.getConfiguration()
-    or
-    additionalLocalFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    mid.getAp() instanceof PartialAccessPathNil and
-    ap = TPartialNil(getErasedRepr(node.getType())) and
-    config = mid.getConfiguration()
+    not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall()) and
+    (
+      localFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      ap = mid.getAp() and
+      config = mid.getConfiguration()
+      or
+      additionalLocalFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      mid.getAp() instanceof PartialAccessPathNil and
+      ap = TPartialNil(getErasedRepr(node.getType())) and
+      config = mid.getConfiguration()
+    )
     or
     jumpStep(mid.getNode(), node, config) and
     cc instanceof CallContextAny and
@@ -2378,7 +2392,7 @@ private module FlowExploration {
       partialPathIntoCallable0(mid, callable, i, outercc, call, emptyAp, ap, config) and
       p.isParameterOf(callable, i)
     |
-      if reducedViableImplInCallContext(_, callable, call)
+      if recordDataFlowCallSite(call, callable)
       then innercc = TSpecificCall(call, i, emptyAp)
       else innercc = TSomeCall(p, emptyAp)
     )

cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowImpl4.qll

@@ -905,30 +905,35 @@ private predicate localFlowExit(Node node, Configuration config) {
  */
 pragma[nomagic]
 private predicate localFlowStepPlus(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext cc
 ) {
-  localFlowEntry(node1, config) and
+  not isUnreachableInCall(node2, cc.(LocalCallContextSpecificCall).getCall()) and
   (
-    localFlowStep(node1, node2, config) and preservesValue = true
+    localFlowEntry(node1, config) and
+    (
+      localFlowStep(node1, node2, config) and preservesValue = true
+      or
+      additionalLocalFlowStep(node1, node2, config) and preservesValue = false
+    ) and
+    node1 != node2 and
+    cc.relevantFor(node1.getEnclosingCallable()) and
+    not isUnreachableInCall(node1, cc.(LocalCallContextSpecificCall).getCall()) and
+    nodeCand(node2, unbind(config))
     or
-    additionalLocalFlowStep(node1, node2, config) and preservesValue = false
-  ) and
-  node1 != node2 and
-  nodeCand(node2, unbind(config))
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, preservesValue, config) and
-    localFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    nodeCand(node2, unbind(config))
-  )
-  or
-  exists(Node mid |
-    localFlowStepPlus(node1, mid, _, config) and
-    additionalLocalFlowStep(mid, node2, config) and
-    not mid instanceof CastNode and
-    preservesValue = false and
-    nodeCand(node2, unbind(config))
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, preservesValue, config, cc) and
+      localFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      nodeCand(node2, unbind(config))
+    )
+    or
+    exists(Node mid |
+      localFlowStepPlus(node1, mid, _, config, cc) and
+      additionalLocalFlowStep(mid, node2, config) and
+      not mid instanceof CastNode and
+      preservesValue = false and
+      nodeCand(node2, unbind(config))
+    )
   )
 }
 
@@ -936,11 +941,11 @@ private predicate localFlowStepPlus(
  * Holds if `node1` can step to `node2` in one or more local steps and this
  * path can occur as a maximal subsequence of local steps in a dataflow path.
  */
-pragma[noinline]
+pragma[nomagic]
 private predicate localFlowBigStep(
-  Node node1, Node node2, boolean preservesValue, Configuration config
+  Node node1, Node node2, boolean preservesValue, Configuration config, LocalCallContext callContext
 ) {
-  localFlowStepPlus(node1, node2, preservesValue, config) and
+  localFlowStepPlus(node1, node2, preservesValue, config, callContext) and
   localFlowExit(node2, config)
 }
 
@@ -1000,7 +1005,7 @@ private class AccessPathFrontNilNode extends Node {
     (
       any(Configuration c).isSource(this)
       or
-      localFlowBigStep(_, this, false, _)
+      localFlowBigStep(_, this, false, _, _)
       or
       additionalJumpStep(_, this, _)
     )
@@ -1023,12 +1028,12 @@ private predicate flowCandFwd0(Node node, boolean fromArg, AccessPathFront apf,
   (
     exists(Node mid |
       flowCandFwd(mid, fromArg, apf, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathFrontNil nil |
       flowCandFwd(mid, fromArg, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       apf = node.(AccessPathFrontNilNode).getApf()
     )
     or
@@ -1122,13 +1127,13 @@ private predicate flowCand0(Node node, boolean toReturn, AccessPathFront apf, Co
   apf instanceof AccessPathFrontNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flowCand(mid, toReturn, apf, config)
   )
   or
   exists(Node mid, AccessPathFrontNil nil |
     flowCandFwd(node, _, apf, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flowCand(mid, toReturn, nil, config) and
     apf instanceof AccessPathFrontNil
   )
@@ -1261,7 +1266,7 @@ abstract private class AccessPath extends TAccessPath {
 
 private class AccessPathNil extends AccessPath, TNil {
   override string toString() {
-    exists(DataFlowType t | this = TNil(t) | result = concat(" : " + ppReprType(t)))
+    exists(DataFlowType t | this = TNil(t) | result = concat(": " + ppReprType(t)))
   }
 
   override AccessPathFront getFront() {
@@ -1277,7 +1282,7 @@ private class AccessPathConsNil extends AccessPathCons, TConsNil {
   override string toString() {
     exists(Content f, DataFlowType t | this = TConsNil(f, t) |
       // The `concat` becomes "" if `ppReprType` has no result.
-      result = f.toString() + concat(" : " + ppReprType(t))
+      result = "[" + f.toString() + "]" + concat(" : " + ppReprType(t))
     )
   }
 
@@ -1294,8 +1299,8 @@ private class AccessPathConsCons extends AccessPathCons, TConsCons {
   override string toString() {
     exists(Content f1, Content f2, int len | this = TConsCons(f1, f2, len) |
       if len = 2
-      then result = f1.toString() + ", " + f2.toString()
-      else result = f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")"
+      then result = "[" + f1.toString() + ", " + f2.toString() + "]"
+      else result = "[" + f1.toString() + ", " + f2.toString() + ", ... (" + len.toString() + ")]"
     )
   }
 
@@ -1363,12 +1368,12 @@ private predicate flowFwd0(
   (
     exists(Node mid |
       flowFwd(mid, fromArg, apf, ap, config) and
-      localFlowBigStep(mid, node, true, config)
+      localFlowBigStep(mid, node, true, config, _)
     )
     or
     exists(Node mid, AccessPathNil nil |
       flowFwd(mid, fromArg, _, nil, config) and
-      localFlowBigStep(mid, node, false, config) and
+      localFlowBigStep(mid, node, false, config, _) and
       ap = node.(AccessPathNilNode).getAp() and
       apf = ap.(AccessPathNil).getFront()
     )
@@ -1472,13 +1477,13 @@ private predicate flow0(Node node, boolean toReturn, AccessPath ap, Configuratio
   ap instanceof AccessPathNil
   or
   exists(Node mid |
-    localFlowBigStep(node, mid, true, config) and
+    localFlowBigStep(node, mid, true, config, _) and
     flow(mid, toReturn, ap, config)
   )
   or
   exists(Node mid, AccessPathNil nil |
     flowFwd(node, _, _, ap, config) and
-    localFlowBigStep(node, mid, false, config) and
+    localFlowBigStep(node, mid, false, config, _) and
     flow(mid, toReturn, nil, config) and
     ap instanceof AccessPathNil
   )
@@ -1626,7 +1631,7 @@ abstract class PathNode extends TPathNode {
     this instanceof PathNodeSink and result = ""
     or
     exists(string s | s = this.(PathNodeMid).getAp().toString() |
-      if s = "" then result = "" else result = " [" + s + "]"
+      if s = "" then result = "" else result = " " + s
     )
   }
 
@@ -1729,14 +1734,20 @@ private class PathNodeSink extends PathNode, TPathNodeSink {
  * a callable is recorded by `cc`.
  */
 private predicate pathStep(PathNodeMid mid, Node node, CallContext cc, AccessPath ap) {
-  localFlowBigStep(mid.getNode(), node, true, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  ap = mid.getAp()
-  or
-  localFlowBigStep(mid.getNode(), node, false, mid.getConfiguration()) and
-  cc = mid.getCallContext() and
-  mid.getAp() instanceof AccessPathNil and
-  ap = node.(AccessPathNilNode).getAp()
+  exists(LocalCallContext localCC, AccessPath ap0, Node midnode, Configuration conf |
+    midnode = mid.getNode() and
+    conf = mid.getConfiguration() and
+    cc = mid.getCallContext() and
+    localCC = getLocalCallContext(cc, midnode.getEnclosingCallable()) and
+    ap0 = mid.getAp()
+  |
+    localFlowBigStep(midnode, node, true, conf, localCC) and
+    ap = ap0
+    or
+    localFlowBigStep(midnode, node, false, conf, localCC) and
+    ap0 instanceof AccessPathNil and
+    ap = node.(AccessPathNilNode).getAp()
+  )
   or
   jumpStep(mid.getNode(), node, mid.getConfiguration()) and
   cc instanceof CallContextAny and
@@ -1880,7 +1891,7 @@ private predicate pathIntoCallable(
     pathIntoCallable0(mid, callable, i, outercc, call, emptyAp) and
     p.isParameterOf(callable, i)
   |
-    if reducedViableImplInCallContext(_, callable, call)
+    if recordDataFlowCallSite(call, callable)
     then innercc = TSpecificCall(call, i, emptyAp)
     else innercc = TSomeCall(p, emptyAp)
   )
@@ -2071,7 +2082,7 @@ private module FlowExploration {
 
   private class PartialAccessPathNil extends PartialAccessPath, TPartialNil {
     override string toString() {
-      exists(DataFlowType t | this = TPartialNil(t) | result = concat(" : " + ppReprType(t)))
+      exists(DataFlowType t | this = TPartialNil(t) | result = concat(": " + ppReprType(t)))
     }
 
     override AccessPathFront getFront() {
@@ -2083,8 +2094,8 @@ private module FlowExploration {
     override string toString() {
       exists(Content f, int len | this = TPartialCons(f, len) |
         if len = 1
-        then result = f.toString()
-        else result = f.toString() + ", ... (" + len.toString() + ")"
+        then result = "[" + f.toString() + "]"
+        else result = "[" + f.toString() + ", ... (" + len.toString() + ")]"
       )
     }
 
@@ -2161,7 +2172,7 @@ private module FlowExploration {
 
     private string ppAp() {
       exists(string s | s = this.(PartialPathNodePriv).getAp().toString() |
-        if s = "" then result = "" else result = " [" + s + "]"
+        if s = "" then result = "" else result = " " + s
       )
     }
 
@@ -2205,16 +2216,19 @@ private module FlowExploration {
   private predicate partialPathStep(
     PartialPathNodePriv mid, Node node, CallContext cc, PartialAccessPath ap, Configuration config
   ) {
-    localFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    ap = mid.getAp() and
-    config = mid.getConfiguration()
-    or
-    additionalLocalFlowStep(mid.getNode(), node, config) and
-    cc = mid.getCallContext() and
-    mid.getAp() instanceof PartialAccessPathNil and
-    ap = TPartialNil(getErasedRepr(node.getType())) and
-    config = mid.getConfiguration()
+    not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall()) and
+    (
+      localFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      ap = mid.getAp() and
+      config = mid.getConfiguration()
+      or
+      additionalLocalFlowStep(mid.getNode(), node, config) and
+      cc = mid.getCallContext() and
+      mid.getAp() instanceof PartialAccessPathNil and
+      ap = TPartialNil(getErasedRepr(node.getType())) and
+      config = mid.getConfiguration()
+    )
     or
     jumpStep(mid.getNode(), node, config) and
     cc instanceof CallContextAny and
@@ -2378,7 +2392,7 @@ private module FlowExploration {
       partialPathIntoCallable0(mid, callable, i, outercc, call, emptyAp, ap, config) and
       p.isParameterOf(callable, i)
     |
-      if reducedViableImplInCallContext(_, callable, call)
+      if recordDataFlowCallSite(call, callable)
       then innercc = TSpecificCall(call, i, emptyAp)
       else innercc = TSomeCall(p, emptyAp)
     )

cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowImplCommon.qll

@@ -120,13 +120,16 @@ private module ImplCommon {
         int i, ArgumentNode arg, CallContext outercc, DataFlowCall call
       ) {
         exists(DataFlowCallable c | argumentOf(call, i, arg, c) |
-          outercc = TAnyCallContext()
-          or
-          outercc = TSomeCall(getAParameter(c), _)
-          or
-          exists(DataFlowCall other | outercc = TSpecificCall(other, _, _) |
-            reducedViableImplInCallContext(_, c, other)
-          )
+          (
+            outercc = TAnyCallContext()
+            or
+            outercc = TSomeCall(getAParameter(c), _)
+            or
+            exists(DataFlowCall other | outercc = TSpecificCall(other, _, _) |
+              recordDataFlowCallSite(other, c)
+            )
+          ) and
+          not isUnreachableInCall(arg, outercc.(CallContextSpecificCall).getCall())
         )
       }
 
@@ -152,7 +155,7 @@ private module ImplCommon {
         exists(int i, DataFlowCallable callable |
           viableParamArg1(p, callable, i, arg, outercc, call)
         |
-          if reducedViableImplInCallContext(_, callable, call)
+          if recordDataFlowCallSite(call, callable)
           then innercc = TSpecificCall(call, i, true)
           else innercc = TSomeCall(p, true)
         )
@@ -164,7 +167,7 @@ private module ImplCommon {
         exists(DataFlowCall call, int i, DataFlowCallable callable |
           result = TSpecificCall(call, i, _) and
           p.isParameterOf(callable, i) and
-          reducedViableImplInCallContext(_, callable, call)
+          recordDataFlowCallSite(call, callable)
         )
       }
 
@@ -180,14 +183,16 @@ private module ImplCommon {
         exists(Node mid |
           parameterValueFlow(p, mid, cc) and
           step(mid, node) and
-          compatibleTypes(p.getType(), node.getType())
+          compatibleTypes(p.getType(), node.getType()) and
+          not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall())
         )
         or
         // flow through a callable
         exists(Node arg |
           parameterValueFlow(p, arg, cc) and
           argumentValueFlowsThrough(arg, node, cc) and
-          compatibleTypes(p.getType(), node.getType())
+          compatibleTypes(p.getType(), node.getType()) and
+          not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall())
         )
       }
 
@@ -220,6 +225,7 @@ private module ImplCommon {
           argumentValueFlowsThrough0(call, arg, kind, cc)
         |
           out = getAnOutNode(call, kind) and
+          not isUnreachableInCall(out, cc.(CallContextSpecificCall).getCall()) and
           compatibleTypes(arg.getType(), out.getType())
         )
       }
@@ -462,13 +468,16 @@ private module ImplCommon {
         int i, ArgumentNode arg, CallContext outercc, DataFlowCall call
       ) {
         exists(DataFlowCallable c | argumentOf(call, i, arg, c) |
-          outercc = TAnyCallContext()
-          or
-          outercc = TSomeCall(getAParameter(c), _)
-          or
-          exists(DataFlowCall other | outercc = TSpecificCall(other, _, _) |
-            reducedViableImplInCallContext(_, c, other)
-          )
+          (
+            outercc = TAnyCallContext()
+            or
+            outercc = TSomeCall(getAParameter(c), _)
+            or
+            exists(DataFlowCall other | outercc = TSpecificCall(other, _, _) |
+              recordDataFlowCallSite(other, c)
+            )
+          ) and
+          not isUnreachableInCall(arg, outercc.(CallContextSpecificCall).getCall())
         )
       }
 
@@ -494,7 +503,7 @@ private module ImplCommon {
         exists(int i, DataFlowCallable callable |
           viableParamArg1(p, callable, i, arg, outercc, call)
         |
-          if reducedViableImplInCallContext(_, callable, call)
+          if recordDataFlowCallSite(call, callable)
           then innercc = TSpecificCall(call, i, true)
           else innercc = TSomeCall(p, true)
         )
@@ -506,7 +515,7 @@ private module ImplCommon {
         exists(DataFlowCall call, int i, DataFlowCallable callable |
           result = TSpecificCall(call, i, _) and
           p.isParameterOf(callable, i) and
-          reducedViableImplInCallContext(_, callable, call)
+          recordDataFlowCallSite(call, callable)
         )
       }
 
@@ -522,14 +531,16 @@ private module ImplCommon {
         exists(Node mid |
           parameterValueFlow(p, mid, cc) and
           step(mid, node) and
-          compatibleTypes(p.getType(), node.getType())
+          compatibleTypes(p.getType(), node.getType()) and
+          not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall())
         )
         or
         // flow through a callable
         exists(Node arg |
           parameterValueFlow(p, arg, cc) and
           argumentValueFlowsThrough(arg, node, cc) and
-          compatibleTypes(p.getType(), node.getType())
+          compatibleTypes(p.getType(), node.getType()) and
+          not isUnreachableInCall(node, cc.(CallContextSpecificCall).getCall())
         )
       }
 
@@ -562,6 +573,7 @@ private module ImplCommon {
           argumentValueFlowsThrough0(call, arg, kind, cc)
         |
           out = getAnOutNode(call, kind) and
+          not isUnreachableInCall(out, cc.(CallContextSpecificCall).getCall()) and
           compatibleTypes(arg.getType(), out.getType())
         )
       }
@@ -575,11 +587,22 @@ private module ImplCommon {
       exists(ArgumentNode arg | arg.argumentOf(call, -1))
     }
 
+    /**
+     * Holds if the call context `call` either improves virtual dispatch in
+     * `callable` or if it allows us to prune unreachable nodes in `callable`.
+     */
+    cached
+    predicate recordDataFlowCallSite(DataFlowCall call, DataFlowCallable callable) {
+      reducedViableImplInCallContext(_, callable, call)
+      or
+      exists(Node n | n.getEnclosingCallable() = callable | isUnreachableInCall(n, call))
+    }
+
     cached
     newtype TCallContext =
       TAnyCallContext() or
       TSpecificCall(DataFlowCall call, int i, boolean emptyAp) {
-        reducedViableImplInCallContext(_, _, call) and
+        recordDataFlowCallSite(call, _) and
         (emptyAp = true or emptyAp = false) and
         (
           exists(call.getArgument(i))
@@ -593,6 +616,11 @@ private module ImplCommon {
     cached
     newtype TReturnPosition =
       TReturnPosition0(DataFlowCallable c, ReturnKind kind) { returnPosition(_, c, kind) }
+
+    cached
+    newtype TLocalFlowCallContext =
+      TAnyLocalCall() or
+      TSpecificLocalCall(DataFlowCall call) { isUnreachableInCall(_, call) }
   }
 
   pragma[noinline]
@@ -602,14 +630,15 @@ private module ImplCommon {
   }
 
   /**
-   * A call context to restrict the targets of virtual dispatch and match the
-   * call sites of flow into a method with flow out of a method.
+   * A call context to restrict the targets of virtual dispatch, prune local flow,
+   * and match the call sites of flow into a method with flow out of a method.
    *
    * There are four cases:
    * - `TAnyCallContext()` : No restrictions on method flow.
    * - `TSpecificCall(DataFlowCall call, int i)` : Flow entered through the `i`th
    *    parameter at the given `call`. This call improves the set of viable
-   *    dispatch targets for at least one method call in the current callable.
+   *    dispatch targets for at least one method call in the current callable
+   *    or helps prune unreachable nodes in the current callable.
    * - `TSomeCall(ParameterNode p)` : Flow entered through parameter `p`. The
    *    originating call does not improve the set of dispatch targets for any
    *    method call in the current callable and was therefore not recorded.
@@ -619,10 +648,15 @@ private module ImplCommon {
    */
   abstract class CallContext extends TCallContext {
     abstract string toString();
+
+    /** Holds if this call context is relevant for `callable`. */
+    abstract predicate relevantFor(DataFlowCallable callable);
   }
 
   class CallContextAny extends CallContext, TAnyCallContext {
     override string toString() { result = "CcAny" }
+
+    override predicate relevantFor(DataFlowCallable callable) { any() }
   }
 
   abstract class CallContextCall extends CallContext { }
@@ -633,16 +667,73 @@ private module ImplCommon {
         result = "CcCall(" + call + ", " + i + ")"
       )
     }
+
+    override predicate relevantFor(DataFlowCallable callable) {
+      recordDataFlowCallSite(getCall(), callable)
+    }
+
+    DataFlowCall getCall() { this = TSpecificCall(result, _, _) }
   }
 
   class CallContextSomeCall extends CallContextCall, TSomeCall {
     override string toString() { result = "CcSomeCall" }
+
+    override predicate relevantFor(DataFlowCallable callable) {
+      exists(ParameterNode p | this = TSomeCall(p, _) and p.getEnclosingCallable() = callable)
+    }
   }
 
   class CallContextReturn extends CallContext, TReturn {
     override string toString() {
       exists(DataFlowCall call | this = TReturn(_, call) | result = "CcReturn(" + call + ")")
     }
+
+    override predicate relevantFor(DataFlowCallable callable) {
+      exists(DataFlowCall call | this = TReturn(_, call) and call.getEnclosingCallable() = callable)
+    }
+  }
+
+  /**
+   * A call context that is relevant for pruning local flow.
+   */
+  abstract class LocalCallContext extends TLocalFlowCallContext {
+    abstract string toString();
+
+    /** Holds if this call context is relevant for `callable`. */
+    abstract predicate relevantFor(DataFlowCallable callable);
+  }
+
+  class LocalCallContextAny extends LocalCallContext, TAnyLocalCall {
+    override string toString() { result = "LocalCcAny" }
+
+    override predicate relevantFor(DataFlowCallable callable) { any() }
+  }
+
+  class LocalCallContextSpecificCall extends LocalCallContext, TSpecificLocalCall {
+    LocalCallContextSpecificCall() { this = TSpecificLocalCall(call) }
+
+    DataFlowCall call;
+
+    DataFlowCall getCall() { result = call }
+
+    override string toString() { result = "LocalCcCall(" + call + ")" }
+
+    override predicate relevantFor(DataFlowCallable callable) { relevantLocalCCtx(call, callable) }
+  }
+
+  private predicate relevantLocalCCtx(DataFlowCall call, DataFlowCallable callable) {
+    exists(Node n | n.getEnclosingCallable() = callable and isUnreachableInCall(n, call))
+  }
+
+  /**
+   * Gets the local call context given the call context and the callable that
+   * the contexts apply to.
+   */
+  LocalCallContext getLocalCallContext(CallContext ctx, DataFlowCallable callable) {
+    ctx.relevantFor(callable) and
+    if relevantLocalCCtx(ctx.(CallContextSpecificCall).getCall(), callable)
+    then result.(LocalCallContextSpecificCall).getCall() = ctx.(CallContextSpecificCall).getCall()
+    else result instanceof LocalCallContextAny
   }
 
   /** A callable tagged with a relevant return kind. */

cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll

@@ -204,3 +204,5 @@ class DataFlowCall extends CallInstruction {
 
   Function getEnclosingCallable() { result = this.getEnclosingFunction() }
 }
+
+predicate isUnreachableInCall(Node n, DataFlowCall call) { none() } // stub implementation

cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowUtil.qll

@@ -5,6 +5,7 @@
 private import cpp
 private import semmle.code.cpp.ir.IR
 private import semmle.code.cpp.controlflow.IRGuards
+private import semmle.code.cpp.ir.ValueNumbering
 
 /**
  * A newtype wrapper to prevent accidental casts between `Node` and
@@ -213,6 +214,14 @@ private predicate simpleInstructionLocalFlowStep(Instruction iFrom, Instruction
  */
 predicate localFlow(Node source, Node sink) { localFlowStep*(source, sink) }
 
+/**
+ * Holds if data can flow from `i1` to `i2` in zero or more
+ * local (intra-procedural) steps.
+ */
+predicate localInstructionFlow(Instruction e1, Instruction e2) {
+  localFlow(instructionNode(e1), instructionNode(e2))
+}
+
 /**
  * Holds if data can flow from `e1` to `e2` in zero or more
  * local (intra-procedural) steps.
@@ -220,7 +229,7 @@ predicate localFlow(Node source, Node sink) { localFlowStep*(source, sink) }
 predicate localExprFlow(Expr e1, Expr e2) { localFlow(exprNode(e1), exprNode(e2)) }
 
 /**
- * A guard that validates some expression.
+ * A guard that validates some instruction.
  *
  * To use this in a configuration, extend the class and provide a
  * characteristic predicate precisely specifying the guard, and override
@@ -229,11 +238,15 @@ predicate localExprFlow(Expr e1, Expr e2) { localFlow(exprNode(e1), exprNode(e2)
  * It is important that all extending classes in scope are disjoint.
  */
 class BarrierGuard extends IRGuardCondition {
-  /** NOT YET SUPPORTED. Holds if this guard validates `e` upon evaluating to `b`. */
-  abstract deprecated predicate checks(Instruction e, boolean b);
+  /** Override this predicate to hold if this guard validates `instr` upon evaluating to `b`. */
+  abstract predicate checks(Instruction instr, boolean b);
 
   /** Gets a node guarded by this guard. */
   final Node getAGuardedNode() {
-    none() // stub
+    exists(ValueNumber value, boolean edge |
+      result.asInstruction() = value.getAnInstruction() and
+      this.checks(value.getAnInstruction(), edge) and
+      this.controls(result.asInstruction().getBlock(), edge)
+    )
   }
 }

cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/TaintTrackingUtil.qll

@@ -53,6 +53,14 @@ private predicate localInstructionTaintStep(Instruction nodeFrom, Instruction no
  */
 predicate localTaint(DataFlow::Node source, DataFlow::Node sink) { localTaintStep*(source, sink) }
 
+/**
+ * Holds if taint can flow from `i1` to `i2` in zero or more
+ * local (intra-procedural) steps.
+ */
+predicate localInstructionTaint(Instruction i1, Instruction i2) {
+  localTaint(DataFlow::instructionNode(i1), DataFlow::instructionNode(i2))
+}
+
 /**
  * Holds if taint can flow from `e1` to `e2` in zero or more
  * local (intra-procedural) steps.

cpp/ql/src/semmle/code/cpp/ir/implementation/IRType.qll

@@ -0,0 +1,247 @@
+/**
+ * Minimal, language-neutral type system for the IR.
+ */
+
+private import internal.IRTypeInternal
+
+private newtype TIRType =
+  TIRVoidType() or
+  TIRUnknownType() or
+  TIRErrorType() { Language::hasErrorType() } or
+  TIRBooleanType(int byteSize) { Language::hasBooleanType(byteSize) } or
+  TIRSignedIntegerType(int byteSize) { Language::hasSignedIntegerType(byteSize) } or
+  TIRUnsignedIntegerType(int byteSize) { Language::hasUnsignedIntegerType(byteSize) } or
+  TIRFloatingPointType(int byteSize) { Language::hasFloatingPointType(byteSize) } or
+  TIRAddressType(int byteSize) { Language::hasAddressType(byteSize) } or
+  TIRFunctionAddressType(int byteSize) { Language::hasFunctionAddressType(byteSize) } or
+  TIROpaqueType(Language::OpaqueTypeTag tag, int byteSize) {
+    Language::hasOpaqueType(tag, byteSize)
+  }
+
+/**
+ * The language-neutral type of an IR `Instruction`, `Operand`, or `IRVariable`.
+ * The interface to `IRType` and its subclasses is the same across all languages for which the IR
+ * is supported, so analyses that expect to be used for multiple languages should generally use
+ * `IRType` rather than a language-specific type.
+ *
+ * Many types from the language-specific type system will map to a single canonical `IRType`. Two
+ * types that map to the same `IRType` are considered equivalent by the IR. As an example, in C++,
+ * all pointer types map to the same instance of `IRAddressType`.
+ */
+class IRType extends TIRType {
+  string toString() { none() }
+
+  /**
+   * Gets a string that uniquely identifies this `IRType`. This string is often the same as the
+   * result of `IRType.toString()`, but for some types it may be more verbose to ensure uniqueness.
+   */
+  string getIdentityString() { result = toString() }
+
+  /**
+   * Gets the size of the type, in bytes, if known.
+   *
+   * This will hold for all `IRType` objects except `IRUnknownType`.
+   */
+  int getByteSize() { none() }
+
+  /**
+   * Gets a single instance of `LanguageType` that maps to this `IRType`.
+   */
+  Language::LanguageType getCanonicalLanguageType() { none() }
+}
+
+/**
+ * An unknown type. Generally used to represent results and operands that access an unknown set of
+ * memory locations, such as the side effects of a function call.
+ */
+class IRUnknownType extends IRType, TIRUnknownType {
+  final override string toString() { result = "unknown" }
+
+  final override int getByteSize() { none() }
+
+  final override Language::LanguageType getCanonicalLanguageType() {
+    result = Language::getCanonicalUnknownType()
+  }
+}
+
+/**
+ * A void type, which has no values. Used to represent the result type of an instruction that does
+ * not produce a result.
+ */
+class IRVoidType extends IRType, TIRVoidType {
+  final override string toString() { result = "void" }
+
+  final override int getByteSize() { result = 0 }
+
+  final override Language::LanguageType getCanonicalLanguageType() {
+    result = Language::getCanonicalVoidType()
+  }
+}
+
+/**
+ * An error type. Used when an error in the source code prevents the extractor from determining the
+ * proper type.
+ */
+class IRErrorType extends IRType, TIRErrorType {
+  final override string toString() { result = "error" }
+
+  final override int getByteSize() { result = 0 }
+
+  final override Language::LanguageType getCanonicalLanguageType() {
+    result = Language::getCanonicalErrorType()
+  }
+}
+
+private class IRSizedType extends IRType {
+  int byteSize;
+
+  IRSizedType() {
+    this = TIRBooleanType(byteSize) or
+    this = TIRSignedIntegerType(byteSize) or
+    this = TIRUnsignedIntegerType(byteSize) or
+    this = TIRFloatingPointType(byteSize) or
+    this = TIRAddressType(byteSize) or
+    this = TIRFunctionAddressType(byteSize) or
+    this = TIROpaqueType(_, byteSize)
+  }
+
+  final override int getByteSize() { result = byteSize }
+}
+
+/**
+ * A Boolean type, which can hold the values `true` (non-zero) or `false` (zero).
+ */
+class IRBooleanType extends IRSizedType, TIRBooleanType {
+  final override string toString() { result = "bool" + byteSize.toString() }
+
+  final override Language::LanguageType getCanonicalLanguageType() {
+    result = Language::getCanonicalBooleanType(byteSize)
+  }
+}
+
+/**
+ * A numberic type. This includes `IRSignedIntegerType`, `IRUnsignedIntegerType`, and
+ * `IRFloatingPointType`.
+ */
+class IRNumericType extends IRSizedType {
+  IRNumericType() {
+    this = TIRSignedIntegerType(byteSize) or
+    this = TIRUnsignedIntegerType(byteSize) or
+    this = TIRFloatingPointType(byteSize)
+  }
+}
+
+/**
+ * A signed two's-complement integer. Also used to represent enums whose underlying type is a signed
+ * integer, as well as character types whose representation is signed.
+ */
+class IRSignedIntegerType extends IRNumericType, TIRSignedIntegerType {
+  final override string toString() { result = "int" + byteSize.toString() }
+
+  final override Language::LanguageType getCanonicalLanguageType() {
+    result = Language::getCanonicalSignedIntegerType(byteSize)
+  }
+}
+
+/**
+ * An unsigned two's-complement integer. Also used to represent enums whose underlying type is an
+ * unsigned integer, as well as character types whose representation is unsigned.
+ */
+class IRUnsignedIntegerType extends IRNumericType, TIRUnsignedIntegerType {
+  final override string toString() { result = "uint" + byteSize.toString() }
+
+  final override Language::LanguageType getCanonicalLanguageType() {
+    result = Language::getCanonicalUnsignedIntegerType(byteSize)
+  }
+}
+
+/**
+ * A floating-point type.
+ */
+class IRFloatingPointType extends IRNumericType, TIRFloatingPointType {
+  final override string toString() { result = "float" + byteSize.toString() }
+
+  final override Language::LanguageType getCanonicalLanguageType() {
+    result = Language::getCanonicalFloatingPointType(byteSize)
+  }
+}
+
+/**
+ * An address type, representing the memory address of data. Used to represent pointers, references,
+ * and lvalues, include those that are garbage collected.
+ *
+ * The address of a function is represented by the separate `IRFunctionAddressType`.
+ */
+class IRAddressType extends IRSizedType, TIRAddressType {
+  final override string toString() { result = "addr" + byteSize.toString() }
+
+  final override Language::LanguageType getCanonicalLanguageType() {
+    result = Language::getCanonicalAddressType(byteSize)
+  }
+}
+
+/**
+ * An address type, representing the memory address of code. Used to represent function pointers,
+ * function references, and the target of a direct function call.
+ */
+class IRFunctionAddressType extends IRSizedType, TIRFunctionAddressType {
+  final override string toString() { result = "func" + byteSize.toString() }
+
+  final override Language::LanguageType getCanonicalLanguageType() {
+    result = Language::getCanonicalFunctionAddressType(byteSize)
+  }
+}
+
+/**
+ * A type with known size that does not fit any of the other kinds of type. Used to represent
+ * classes, structs, unions, fixed-size arrays, pointers-to-member, and more.
+ */
+class IROpaqueType extends IRSizedType, TIROpaqueType {
+  Language::OpaqueTypeTag tag;
+
+  IROpaqueType() { this = TIROpaqueType(tag, byteSize) }
+
+  final override string toString() {
+    result = "opaque" + byteSize.toString() + "{" + tag.toString() + "}"
+  }
+
+  final override string getIdentityString() {
+    result = "opaque" + byteSize.toString() + "{" + Language::getOpaqueTagIdentityString(tag) + "}"
+  }
+
+  final override Language::LanguageType getCanonicalLanguageType() {
+    result = Language::getCanonicalOpaqueType(tag, byteSize)
+  }
+
+  /**
+   * Gets the "tag" that differentiates this type from other incompatible opaque types that have the
+   * same size.
+   */
+  final Language::OpaqueTypeTag getTag() { result = tag }
+}
+
+module IRTypeSanity {
+  query predicate missingCanonicalLanguageType(IRType type, string message) {
+    not exists(type.getCanonicalLanguageType()) and
+    message = "Type does not have a canonical `LanguageType`"
+  }
+
+  query predicate multipleCanonicalLanguageTypes(IRType type, string message) {
+    strictcount(type.getCanonicalLanguageType()) > 1 and
+    message = "Type has multiple canonical `LanguageType`s: " +
+        concat(type.getCanonicalLanguageType().toString(), ", ")
+  }
+
+  query predicate missingIRType(Language::LanguageType type, string message) {
+    not exists(type.getIRType()) and
+    message = "`LanguageType` does not have a corresponding `IRType`."
+  }
+
+  query predicate multipleIRTypes(Language::LanguageType type, string message) {
+    strictcount(type.getIRType()) > 1 and
+    message = "`LanguageType` " + type.getAQlClass() + " has multiple `IRType`s: " +
+        concat(type.getIRType().toString(), ", ")
+  }
+
+  import Language::LanguageTypeSanity
+}

cpp/ql/src/semmle/code/cpp/ir/implementation/MemoryAccessKind.qll

@@ -5,6 +5,7 @@ private newtype TMemoryAccessKind =
   TBufferMayMemoryAccess() or
   TEscapedMemoryAccess() or
   TEscapedMayMemoryAccess() or
+  TNonLocalMayMemoryAccess() or
   TPhiMemoryAccess() or
   TUnmodeledMemoryAccess() or
   TChiTotalMemoryAccess() or
@@ -80,6 +81,14 @@ class EscapedMayMemoryAccess extends MemoryAccessKind, TEscapedMayMemoryAccess {
   override string toString() { result = "escaped(may)" }
 }
 
+/**
+ * The operand or result may access all memory whose address has escaped, other than data on the
+ * stack frame of the current function.
+ */
+class NonLocalMayMemoryAccess extends MemoryAccessKind, TNonLocalMayMemoryAccess {
+  override string toString() { result = "nonlocal(may)" }
+}
+
 /**
  * The operand is a Phi operand, which accesses the same memory as its
  * definition.

cpp/ql/src/semmle/code/cpp/ir/implementation/Opcode.qll

@@ -57,6 +57,7 @@ private newtype TOpcode =
   TUnmodeledDefinition() or
   TUnmodeledUse() or
   TAliasedDefinition() or
+  TAliasedUse() or
   TPhi() or
   TBuiltIn() or
   TVarArgsStart() or
@@ -393,6 +394,10 @@ module Opcode {
     final override string toString() { result = "AliasedDefinition" }
   }
 
+  class AliasedUse extends Opcode, TAliasedUse {
+    final override string toString() { result = "AliasedUse" }
+  }
+
   class Phi extends Opcode, TPhi {
     final override string toString() { result = "Phi" }
   }

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/IR.qll

@@ -5,6 +5,7 @@ import IRVariable
 import Operand
 private import internal.IRImports as Imports
 import Imports::EdgeKind
+import Imports::IRType
 import Imports::MemoryAccessKind
 
 private newtype TIRPropertyProvider = MkIRPropertyProvider()

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/IRSanity.qll

@@ -1,2 +1,3 @@
 private import IR
 import InstructionSanity
+import IRTypeSanity

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/IRVariable.qll

@@ -5,6 +5,7 @@ import Imports::TempVariableTag
 private import Imports::IRUtilities
 private import Imports::TTempVariableTag
 private import Imports::TIRVariable
+private import Imports::IRType
 
 IRUserVariable getIRUserVariable(Language::Function func, Language::Variable var) {
   result.getVariable() = var and
@@ -24,7 +25,17 @@ abstract class IRVariable extends TIRVariable {
   /**
    * Gets the type of the variable.
    */
-  abstract Language::Type getType();
+  final Language::Type getType() { getLanguageType().hasType(result, false) }
+
+  /**
+   * Gets the language-neutral type of the variable.
+   */
+  final IRType getIRType() { result = getLanguageType().getIRType() }
+
+  /**
+   * Gets the type of the variable.
+   */
+  abstract Language::LanguageType getLanguageType();
 
   /**
    * Gets the AST node that declared this variable, or that introduced this
@@ -59,7 +70,7 @@ abstract class IRVariable extends TIRVariable {
  */
 class IRUserVariable extends IRVariable, TIRUserVariable {
   Language::Variable var;
-  Language::Type type;
+  Language::LanguageType type;
 
   IRUserVariable() { this = TIRUserVariable(var, type, func) }
 
@@ -71,7 +82,7 @@ class IRUserVariable extends IRVariable, TIRUserVariable {
     result = getVariable().toString() + " " + getVariable().getLocation().toString()
   }
 
-  final override Language::Type getType() { result = type }
+  final override Language::LanguageType getLanguageType() { result = type }
 
   /**
    * Gets the original user-declared variable.
@@ -110,11 +121,11 @@ IRTempVariable getIRTempVariable(Language::AST ast, TempVariableTag tag) {
 class IRTempVariable extends IRVariable, IRAutomaticVariable, TIRTempVariable {
   Language::AST ast;
   TempVariableTag tag;
-  Language::Type type;
+  Language::LanguageType type;
 
   IRTempVariable() { this = TIRTempVariable(func, ast, tag, type) }
 
-  final override Language::Type getType() { result = type }
+  final override Language::LanguageType getLanguageType() { result = type }
 
   final override Language::AST getAST() { result = ast }
 

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Instruction.qll

@@ -5,6 +5,7 @@ import IRVariable
 import Operand
 private import internal.InstructionImports as Imports
 import Imports::EdgeKind
+import Imports::IRType
 import Imports::MemoryAccessKind
 import Imports::Opcode
 private import Imports::OperandTag
@@ -49,7 +50,8 @@ module InstructionSanity {
         (
           opcode instanceof ReadSideEffectOpcode or
           opcode instanceof Opcode::InlineAsm or
-          opcode instanceof Opcode::CallSideEffect
+          opcode instanceof Opcode::CallSideEffect or
+          opcode instanceof Opcode::AliasedUse
         ) and
         tag instanceof SideEffectOperandTag
       )
@@ -113,13 +115,24 @@ module InstructionSanity {
   }
 
   query predicate missingOperandType(Operand operand, string message) {
-    exists(Language::Function func |
+    exists(Language::Function func, Instruction use |
       not exists(operand.getType()) and
-      func = operand.getUse().getEnclosingFunction() and
-      message = "Operand missing type in function '" + Language::getIdentityString(func) + "'."
+      use = operand.getUse() and
+      func = use.getEnclosingFunction() and
+      message = "Operand '" + operand.toString() + "' of instruction '" + use.getOpcode().toString()
+          + "' missing type in function '" + Language::getIdentityString(func) + "'."
     )
   }
 
+  query predicate sideEffectWithoutPrimary(
+    SideEffectInstruction instr, string message, IRFunction func, string funcText
+  ) {
+    not exists(instr.getPrimaryInstruction()) and
+    message = "Side effect instruction missing primary instruction in function $@" and
+    func = instr.getEnclosingIRFunction() and
+    funcText = Language::getIdentityString(func.getFunction())
+  }
+
   /**
    * Holds if an instruction, other than `ExitFunction`, has no successors.
    */
@@ -251,6 +264,7 @@ module InstructionSanity {
   ) {
     exists(IRBlock useBlock, int useIndex, Instruction defInstr, IRBlock defBlock, int defIndex |
       not useOperand.getUse() instanceof UnmodeledUseInstruction and
+      not defInstr instanceof UnmodeledDefinitionInstruction and
       pointOfEvaluation(useOperand, useBlock, useIndex) and
       defInstr = useOperand.getAnyDef() and
       (
@@ -312,7 +326,7 @@ class Instruction extends Construction::TInstruction {
   }
 
   private string getResultPrefix() {
-    if getResultType() instanceof Language::VoidType
+    if getResultIRType() instanceof IRVoidType
     then result = "v"
     else
       if hasMemoryResult()
@@ -344,23 +358,6 @@ class Instruction extends Construction::TInstruction {
     )
   }
 
-  bindingset[type]
-  private string getValueCategoryString(string type) {
-    if isGLValue() then result = "glval<" + type + ">" else result = type
-  }
-
-  string getResultTypeString() {
-    exists(string valcat |
-      valcat = getValueCategoryString(getResultType().toString()) and
-      if
-        getResultType() instanceof Language::UnknownType and
-        not isGLValue() and
-        exists(getResultSize())
-      then result = valcat + "[" + getResultSize().toString() + "]"
-      else result = valcat
-    )
-  }
-
   /**
    * Gets a human-readable string that uniquely identifies this instruction
    * within the function. This string is used to refer to this instruction when
@@ -380,7 +377,9 @@ class Instruction extends Construction::TInstruction {
    *
    * Example: `r1_1(int*)`
    */
-  final string getResultString() { result = getResultId() + "(" + getResultTypeString() + ")" }
+  final string getResultString() {
+    result = getResultId() + "(" + getResultLanguageType().getDumpString() + ")"
+  }
 
   /**
    * Gets a string describing the operands of this instruction, suitable for
@@ -448,6 +447,16 @@ class Instruction extends Construction::TInstruction {
     result = Construction::getInstructionUnconvertedResultExpression(this)
   }
 
+  final Language::LanguageType getResultLanguageType() {
+    result = Construction::getInstructionResultType(this)
+  }
+
+  /**
+   * Gets the type of the result produced by this instruction. If the instruction does not produce
+   * a result, its result type will be `IRVoidType`.
+   */
+  final IRType getResultIRType() { result = getResultLanguageType().getIRType() }
+
   /**
    * Gets the type of the result produced by this instruction. If the
    * instruction does not produce a result, its result type will be `VoidType`.
@@ -455,7 +464,16 @@ class Instruction extends Construction::TInstruction {
    * If `isGLValue()` holds, then the result type of this instruction should be
    * thought of as "pointer to `getResultType()`".
    */
-  final Language::Type getResultType() { Construction::instructionHasType(this, result, _) }
+  final Language::Type getResultType() {
+    exists(Language::LanguageType resultType |
+      resultType = getResultLanguageType() and
+      (
+        resultType.hasUnspecifiedType(result, _)
+        or
+        not resultType.hasUnspecifiedType(_, _) and result instanceof Language::UnknownType
+      )
+    )
+  }
 
   /**
    * Holds if the result produced by this instruction is a glvalue. If this
@@ -475,7 +493,7 @@ class Instruction extends Construction::TInstruction {
    * result of the `Load` instruction is a prvalue of type `int`, representing
    * the integer value loaded from variable `x`.
    */
-  final predicate isGLValue() { Construction::instructionHasType(this, _, true) }
+  final predicate isGLValue() { Construction::getInstructionResultType(this).hasType(_, true) }
 
   /**
    * Gets the size of the result produced by this instruction, in bytes. If the
@@ -484,16 +502,7 @@ class Instruction extends Construction::TInstruction {
    * If `this.isGLValue()` holds for this instruction, the value of
    * `getResultSize()` will always be the size of a pointer.
    */
-  final int getResultSize() {
-    if isGLValue()
-    then
-      // a glvalue is always pointer-sized.
-      result = Language::getPointerSize()
-    else
-      if getResultType() instanceof Language::UnknownType
-      then result = Construction::getInstructionResultSize(this)
-      else result = Language::getTypeSize(getResultType())
-  }
+  final int getResultSize() { result = Construction::getInstructionResultType(this).getByteSize() }
 
   /**
    * Gets the opcode that specifies the operation performed by this instruction.
@@ -611,7 +620,12 @@ class VariableInstruction extends Instruction {
 
   override string getImmediateString() { result = var.toString() }
 
-  final IRVariable getVariable() { result = var }
+  final IRVariable getIRVariable() { result = var }
+
+  /**
+   * Gets the AST variable that this instruction's IR variable refers to, if one exists.
+   */
+  final Language::Variable getASTVariable() { result = var.(IRUserVariable).getVariable() }
 }
 
 class FieldInstruction extends Instruction {
@@ -1370,7 +1384,7 @@ class CatchInstruction extends Instruction {
  * An instruction that catches an exception of a specific type.
  */
 class CatchByTypeInstruction extends CatchInstruction {
-  Language::Type exceptionType;
+  Language::LanguageType exceptionType;
 
   CatchByTypeInstruction() {
     getOpcode() instanceof Opcode::CatchByType and
@@ -1382,7 +1396,7 @@ class CatchByTypeInstruction extends CatchInstruction {
   /**
    * Gets the type of exception to be caught.
    */
-  final Language::Type getExceptionType() { result = exceptionType }
+  final Language::LanguageType getExceptionType() { result = exceptionType }
 }
 
 /**
@@ -1409,6 +1423,13 @@ class AliasedDefinitionInstruction extends Instruction {
   final override MemoryAccessKind getResultMemoryAccess() { result instanceof EscapedMemoryAccess }
 }
 
+/**
+ * An instruction that consumes all escaped memory on exit from the function.
+ */
+class AliasedUseInstruction extends Instruction {
+  AliasedUseInstruction() { getOpcode() instanceof Opcode::AliasedUse }
+}
+
 class UnmodeledUseInstruction extends Instruction {
   UnmodeledUseInstruction() { getOpcode() instanceof Opcode::UnmodeledUse }
 

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Operand.qll

@@ -1,9 +1,10 @@
 private import internal.IRInternal
-import Instruction
-import IRBlock
+private import Instruction
+private import IRBlock
 private import internal.OperandImports as Imports
-import Imports::MemoryAccessKind
-import Imports::Overlap
+private import Imports::MemoryAccessKind
+private import Imports::IRType
+private import Imports::Overlap
 private import Imports::OperandTag
 
 cached
@@ -143,22 +144,40 @@ class Operand extends TOperand {
    * the definition type, such as in the case of a partial read or a read from a pointer that
    * has been cast to a different type.
    */
-  Language::Type getType() { result = getAnyDef().getResultType() }
+  Language::LanguageType getLanguageType() { result = getAnyDef().getResultLanguageType() }
+
+  /**
+   * Gets the language-neutral type of the value consumed by this operand. This is usually the same
+   * as the result type of the definition instruction consumed by this operand. For register
+   * operands, this is always the case. For some memory operands, the operand type may be different
+   * from the definition type, such as in the case of a partial read or a read from a pointer that
+   * has been cast to a different type.
+   */
+  final IRType getIRType() { result = getLanguageType().getIRType() }
+
+  /**
+   * Gets the type of the value consumed by this operand. This is usually the same as the
+   * result type of the definition instruction consumed by this operand. For register operands,
+   * this is always the case. For some memory operands, the operand type may be different from
+   * the definition type, such as in the case of a partial read or a read from a pointer that
+   * has been cast to a different type.
+   */
+  final Language::Type getType() { getLanguageType().hasType(result, _) }
 
   /**
    * Holds if the value consumed by this operand is a glvalue. If this
    * holds, the value of the operand represents the address of a location,
    * and the type of the location is given by `getType()`. If this does
    * not hold, the value of the operand represents a value whose type is
-   * given by `getResultType()`.
+   * given by `getType()`.
    */
-  predicate isGLValue() { getAnyDef().isGLValue() }
+  final predicate isGLValue() { getLanguageType().hasType(_, true) }
 
   /**
    * Gets the size of the value consumed by this operand, in bytes. If the operand does not have
    * a known constant size, this predicate does not hold.
    */
-  int getSize() { result = Language::getTypeSize(getType()) }
+  final int getSize() { result = getLanguageType().getByteSize() }
 }
 
 /**
@@ -170,11 +189,6 @@ class MemoryOperand extends Operand {
     this = TPhiOperand(_, _, _, _)
   }
 
-  override predicate isGLValue() {
-    // A `MemoryOperand` can never be a glvalue
-    none()
-  }
-
   /**
    * Gets the kind of memory access performed by the operand.
    */
@@ -239,7 +253,7 @@ class NonPhiMemoryOperand extends NonPhiOperand, MemoryOperand, TNonPhiMemoryOpe
 class TypedOperand extends NonPhiMemoryOperand {
   override TypedOperandTag tag;
 
-  final override Language::Type getType() {
+  final override Language::LanguageType getLanguageType() {
     result = Construction::getInstructionOperandType(useInstr, tag)
   }
 }
@@ -381,13 +395,10 @@ class PositionalArgumentOperand extends ArgumentOperand {
 class SideEffectOperand extends TypedOperand {
   override SideEffectOperandTag tag;
 
-  final override int getSize() {
-    if getType() instanceof Language::UnknownType
-    then result = Construction::getInstructionOperandSize(useInstr, tag)
-    else result = Language::getTypeSize(getType())
-  }
-
   override MemoryAccessKind getMemoryAccess() {
+    useInstr instanceof AliasedUseInstruction and
+    result instanceof NonLocalMayMemoryAccess
+    or
     useInstr instanceof CallSideEffectInstruction and
     result instanceof EscapedMayMemoryAccess
     or

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/gvn/ValueNumbering.qll

@@ -1,5 +1,5 @@
 private import internal.ValueNumberingInternal
-private import cpp
+private import internal.ValueNumberingImports
 private import IR
 
 /**
@@ -23,31 +23,32 @@ newtype TValueNumber =
     initializeParameterValueNumber(_, irFunc, var)
   } or
   TInitializeThisValueNumber(IRFunction irFunc) { initializeThisValueNumber(_, irFunc) } or
-  TConstantValueNumber(IRFunction irFunc, Type type, string value) {
+  TConstantValueNumber(IRFunction irFunc, IRType type, string value) {
     constantValueNumber(_, irFunc, type, value)
   } or
-  TStringConstantValueNumber(IRFunction irFunc, Type type, string value) {
+  TStringConstantValueNumber(IRFunction irFunc, IRType type, string value) {
     stringConstantValueNumber(_, irFunc, type, value)
   } or
-  TFieldAddressValueNumber(IRFunction irFunc, Field field, ValueNumber objectAddress) {
+  TFieldAddressValueNumber(IRFunction irFunc, Language::Field field, ValueNumber objectAddress) {
     fieldAddressValueNumber(_, irFunc, field, objectAddress)
   } or
   TBinaryValueNumber(
-    IRFunction irFunc, Opcode opcode, Type type, ValueNumber leftOperand, ValueNumber rightOperand
+    IRFunction irFunc, Opcode opcode, IRType type, ValueNumber leftOperand, ValueNumber rightOperand
   ) {
     binaryValueNumber(_, irFunc, opcode, type, leftOperand, rightOperand)
   } or
   TPointerArithmeticValueNumber(
-    IRFunction irFunc, Opcode opcode, Type type, int elementSize, ValueNumber leftOperand,
+    IRFunction irFunc, Opcode opcode, IRType type, int elementSize, ValueNumber leftOperand,
     ValueNumber rightOperand
   ) {
     pointerArithmeticValueNumber(_, irFunc, opcode, type, elementSize, leftOperand, rightOperand)
   } or
-  TUnaryValueNumber(IRFunction irFunc, Opcode opcode, Type type, ValueNumber operand) {
+  TUnaryValueNumber(IRFunction irFunc, Opcode opcode, IRType type, ValueNumber operand) {
     unaryValueNumber(_, irFunc, opcode, type, operand)
   } or
   TInheritanceConversionValueNumber(
-    IRFunction irFunc, Opcode opcode, Class baseClass, Class derivedClass, ValueNumber operand
+    IRFunction irFunc, Opcode opcode, Language::Class baseClass, Language::Class derivedClass,
+    ValueNumber operand
   ) {
     inheritanceConversionValueNumber(_, irFunc, opcode, baseClass, derivedClass, operand)
   } or
@@ -59,7 +60,7 @@ newtype TValueNumber =
 class ValueNumber extends TValueNumber {
   final string toString() { result = getExampleInstruction().getResultId() }
 
-  final Location getLocation() { result = getExampleInstruction().getLocation() }
+  final Language::Location getLocation() { result = getExampleInstruction().getLocation() }
 
   /**
    * Gets the instructions that have been assigned this value number. This will always produce at
@@ -135,14 +136,14 @@ private predicate variableAddressValueNumber(
   VariableAddressInstruction instr, IRFunction irFunc, IRVariable var
 ) {
   instr.getEnclosingIRFunction() = irFunc and
-  instr.getVariable() = var
+  instr.getIRVariable() = var
 }
 
 private predicate initializeParameterValueNumber(
   InitializeParameterInstruction instr, IRFunction irFunc, IRVariable var
 ) {
   instr.getEnclosingIRFunction() = irFunc and
-  instr.getVariable() = var
+  instr.getIRVariable() = var
 }
 
 private predicate initializeThisValueNumber(InitializeThisInstruction instr, IRFunction irFunc) {
@@ -150,23 +151,23 @@ private predicate initializeThisValueNumber(InitializeThisInstruction instr, IRF
 }
 
 private predicate constantValueNumber(
-  ConstantInstruction instr, IRFunction irFunc, Type type, string value
+  ConstantInstruction instr, IRFunction irFunc, IRType type, string value
 ) {
   instr.getEnclosingIRFunction() = irFunc and
-  instr.getResultType() = type and
+  instr.getResultIRType() = type and
   instr.getValue() = value
 }
 
 private predicate stringConstantValueNumber(
-  StringConstantInstruction instr, IRFunction irFunc, Type type, string value
+  StringConstantInstruction instr, IRFunction irFunc, IRType type, string value
 ) {
   instr.getEnclosingIRFunction() = irFunc and
-  instr.getResultType() = type and
+  instr.getResultIRType() = type and
   instr.getValue().getValue() = value
 }
 
 private predicate fieldAddressValueNumber(
-  FieldAddressInstruction instr, IRFunction irFunc, Field field, ValueNumber objectAddress
+  FieldAddressInstruction instr, IRFunction irFunc, Language::Field field, ValueNumber objectAddress
 ) {
   instr.getEnclosingIRFunction() = irFunc and
   instr.getField() = field and
@@ -174,43 +175,43 @@ private predicate fieldAddressValueNumber(
 }
 
 private predicate binaryValueNumber(
-  BinaryInstruction instr, IRFunction irFunc, Opcode opcode, Type type, ValueNumber leftOperand,
+  BinaryInstruction instr, IRFunction irFunc, Opcode opcode, IRType type, ValueNumber leftOperand,
   ValueNumber rightOperand
 ) {
   instr.getEnclosingIRFunction() = irFunc and
   not instr instanceof PointerArithmeticInstruction and
   instr.getOpcode() = opcode and
-  instr.getResultType() = type and
+  instr.getResultIRType() = type and
   valueNumber(instr.getLeft()) = leftOperand and
   valueNumber(instr.getRight()) = rightOperand
 }
 
 private predicate pointerArithmeticValueNumber(
-  PointerArithmeticInstruction instr, IRFunction irFunc, Opcode opcode, Type type, int elementSize,
-  ValueNumber leftOperand, ValueNumber rightOperand
+  PointerArithmeticInstruction instr, IRFunction irFunc, Opcode opcode, IRType type,
+  int elementSize, ValueNumber leftOperand, ValueNumber rightOperand
 ) {
   instr.getEnclosingIRFunction() = irFunc and
   instr.getOpcode() = opcode and
-  instr.getResultType() = type and
+  instr.getResultIRType() = type and
   instr.getElementSize() = elementSize and
   valueNumber(instr.getLeft()) = leftOperand and
   valueNumber(instr.getRight()) = rightOperand
 }
 
 private predicate unaryValueNumber(
-  UnaryInstruction instr, IRFunction irFunc, Opcode opcode, Type type, ValueNumber operand
+  UnaryInstruction instr, IRFunction irFunc, Opcode opcode, IRType type, ValueNumber operand
 ) {
   instr.getEnclosingIRFunction() = irFunc and
   not instr instanceof InheritanceConversionInstruction and
   not instr instanceof CopyInstruction and
   instr.getOpcode() = opcode and
-  instr.getResultType() = type and
+  instr.getResultIRType() = type and
   valueNumber(instr.getUnary()) = operand
 }
 
 private predicate inheritanceConversionValueNumber(
-  InheritanceConversionInstruction instr, IRFunction irFunc, Opcode opcode, Class baseClass,
-  Class derivedClass, ValueNumber operand
+  InheritanceConversionInstruction instr, IRFunction irFunc, Opcode opcode,
+  Language::Class baseClass, Language::Class derivedClass, ValueNumber operand
 ) {
   instr.getEnclosingIRFunction() = irFunc and
   instr.getOpcode() = opcode and
@@ -225,7 +226,7 @@ private predicate inheritanceConversionValueNumber(
  */
 private predicate uniqueValueNumber(Instruction instr, IRFunction irFunc) {
   instr.getEnclosingIRFunction() = irFunc and
-  not instr.getResultType() instanceof VoidType and
+  not instr.getResultIRType() instanceof IRVoidType and
   not numberableInstruction(instr)
 }
 
@@ -269,38 +270,41 @@ private ValueNumber nonUniqueValueNumber(Instruction instr) {
       initializeThisValueNumber(instr, irFunc) and
       result = TInitializeThisValueNumber(irFunc)
       or
-      exists(Type type, string value |
+      exists(IRType type, string value |
         constantValueNumber(instr, irFunc, type, value) and
         result = TConstantValueNumber(irFunc, type, value)
       )
       or
-      exists(Type type, string value |
+      exists(IRType type, string value |
         stringConstantValueNumber(instr, irFunc, type, value) and
         result = TStringConstantValueNumber(irFunc, type, value)
       )
       or
-      exists(Field field, ValueNumber objectAddress |
+      exists(Language::Field field, ValueNumber objectAddress |
         fieldAddressValueNumber(instr, irFunc, field, objectAddress) and
         result = TFieldAddressValueNumber(irFunc, field, objectAddress)
       )
       or
-      exists(Opcode opcode, Type type, ValueNumber leftOperand, ValueNumber rightOperand |
+      exists(Opcode opcode, IRType type, ValueNumber leftOperand, ValueNumber rightOperand |
         binaryValueNumber(instr, irFunc, opcode, type, leftOperand, rightOperand) and
         result = TBinaryValueNumber(irFunc, opcode, type, leftOperand, rightOperand)
       )
       or
-      exists(Opcode opcode, Type type, ValueNumber operand |
+      exists(Opcode opcode, IRType type, ValueNumber operand |
         unaryValueNumber(instr, irFunc, opcode, type, operand) and
         result = TUnaryValueNumber(irFunc, opcode, type, operand)
       )
       or
-      exists(Opcode opcode, Class baseClass, Class derivedClass, ValueNumber operand |
+      exists(
+        Opcode opcode, Language::Class baseClass, Language::Class derivedClass, ValueNumber operand
+      |
         inheritanceConversionValueNumber(instr, irFunc, opcode, baseClass, derivedClass, operand) and
         result = TInheritanceConversionValueNumber(irFunc, opcode, baseClass, derivedClass, operand)
       )
       or
       exists(
-        Opcode opcode, Type type, int elementSize, ValueNumber leftOperand, ValueNumber rightOperand
+        Opcode opcode, IRType type, int elementSize, ValueNumber leftOperand,
+        ValueNumber rightOperand
       |
         pointerArithmeticValueNumber(instr, irFunc, opcode, type, elementSize, leftOperand,
           rightOperand) and

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/gvn/internal/ValueNumberingImports.qll

@@ -0,0 +1,2 @@
+import semmle.code.cpp.ir.internal.Overlap
+import semmle.code.cpp.ir.internal.IRCppLanguage as Language

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasAnalysis.qll

@@ -282,7 +282,7 @@ private predicate automaticVariableAddressEscapes(IRAutomaticVariable var) {
   // The variable's address escapes if the result of any
   // VariableAddressInstruction that computes the variable's address escapes.
   exists(VariableAddressInstruction instr |
-    instr.getVariable() = var and
+    instr.getIRVariable() = var and
     resultEscapesNonReturn(instr)
   )
 }
@@ -305,7 +305,7 @@ predicate variableAddressEscapes(IRVariable var) {
  */
 predicate resultPointsTo(Instruction instr, IRVariable var, IntValue bitOffset) {
   // The address of a variable points to that variable, at offset 0.
-  instr.(VariableAddressInstruction).getVariable() = var and
+  instr.(VariableAddressInstruction).getIRVariable() = var and
   bitOffset = 0
   or
   exists(Operand operand, IntValue originalBitOffset, IntValue propagatedBitOffset |

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasedSSA.qll

@@ -1,6 +1,6 @@
-private import cpp
 import AliasAnalysis
 import semmle.code.cpp.ir.internal.Overlap
+private import semmle.code.cpp.ir.internal.IRCppLanguage as Language
 private import semmle.code.cpp.Print
 private import semmle.code.cpp.ir.implementation.unaliased_ssa.IR
 private import semmle.code.cpp.ir.internal.IntegerConstant as Ints
@@ -10,31 +10,42 @@ private import semmle.code.cpp.ir.implementation.internal.OperandTag
 private class IntValue = Ints::IntValue;
 
 private predicate hasResultMemoryAccess(
-  Instruction instr, IRVariable var, Type type, IntValue startBitOffset, IntValue endBitOffset
+  Instruction instr, IRVariable var, IRType type, Language::LanguageType languageType,
+  IntValue startBitOffset, IntValue endBitOffset
 ) {
   resultPointsTo(instr.getResultAddress(), var, startBitOffset) and
-  type = instr.getResultType() and
-  if exists(instr.getResultSize())
-  then endBitOffset = Ints::add(startBitOffset, Ints::mul(instr.getResultSize(), 8))
+  languageType = instr.getResultLanguageType() and
+  type = languageType.getIRType() and
+  if exists(type.getByteSize())
+  then endBitOffset = Ints::add(startBitOffset, Ints::mul(type.getByteSize(), 8))
   else endBitOffset = Ints::unknown()
 }
 
 private predicate hasOperandMemoryAccess(
-  MemoryOperand operand, IRVariable var, Type type, IntValue startBitOffset, IntValue endBitOffset
+  MemoryOperand operand, IRVariable var, IRType type, Language::LanguageType languageType,
+  IntValue startBitOffset, IntValue endBitOffset
 ) {
   resultPointsTo(operand.getAddressOperand().getAnyDef(), var, startBitOffset) and
-  type = operand.getType() and
-  if exists(operand.getSize())
-  then endBitOffset = Ints::add(startBitOffset, Ints::mul(operand.getSize(), 8))
+  languageType = operand.getLanguageType() and
+  type = languageType.getIRType() and
+  if exists(type.getByteSize())
+  then endBitOffset = Ints::add(startBitOffset, Ints::mul(type.getByteSize(), 8))
   else endBitOffset = Ints::unknown()
 }
 
 private newtype TMemoryLocation =
-  TVariableMemoryLocation(IRVariable var, Type type, IntValue startBitOffset, IntValue endBitOffset) {
-    hasResultMemoryAccess(_, var, type, startBitOffset, endBitOffset) or
-    hasOperandMemoryAccess(_, var, type, startBitOffset, endBitOffset)
+  TVariableMemoryLocation(
+    IRVariable var, IRType type, Language::LanguageType languageType, IntValue startBitOffset,
+    IntValue endBitOffset
+  ) {
+    (
+      hasResultMemoryAccess(_, var, type, _, startBitOffset, endBitOffset) or
+      hasOperandMemoryAccess(_, var, type, _, startBitOffset, endBitOffset)
+    ) and
+    languageType = type.getCanonicalLanguageType()
   } or
   TUnknownMemoryLocation(IRFunction irFunc) or
+  TUnknownNonLocalMemoryLocation(IRFunction irFunc) or
   TUnknownVirtualVariable(IRFunction irFunc)
 
 /**
@@ -49,9 +60,11 @@ abstract class MemoryLocation extends TMemoryLocation {
 
   abstract VirtualVariable getVirtualVariable();
 
-  abstract Type getType();
+  abstract Language::LanguageType getType();
 
   abstract string getUniqueId();
+
+  final IRType getIRType() { result = getType().getIRType() }
 }
 
 abstract class VirtualVariable extends MemoryLocation { }
@@ -62,20 +75,34 @@ abstract class VirtualVariable extends MemoryLocation { }
  */
 class VariableMemoryLocation extends TVariableMemoryLocation, MemoryLocation {
   IRVariable var;
-  Type type;
+  IRType type;
+  Language::LanguageType languageType;
   IntValue startBitOffset;
   IntValue endBitOffset;
 
   VariableMemoryLocation() {
-    this = TVariableMemoryLocation(var, type, startBitOffset, endBitOffset)
+    this = TVariableMemoryLocation(var, type, languageType, startBitOffset, endBitOffset)
   }
 
   final override string toString() {
     result = var.toString() + Interval::getIntervalString(startBitOffset, endBitOffset) + "<" +
-        type.toString() + ">"
+        type.toString() + ", " + languageType.toString() + ">"
   }
 
-  final override Type getType() { result = type }
+  final override Language::LanguageType getType() {
+    if
+      strictcount(Language::LanguageType accessType |
+        hasResultMemoryAccess(_, var, type, accessType, startBitOffset, endBitOffset) or
+        hasOperandMemoryAccess(_, var, type, accessType, startBitOffset, endBitOffset)
+      ) = 1
+    then
+      // All of the accesses have the same `LanguageType`, so just use that.
+      hasResultMemoryAccess(_, var, type, result, startBitOffset, endBitOffset) or
+      hasOperandMemoryAccess(_, var, type, result, startBitOffset, endBitOffset)
+    else
+      // There is no single type for all accesses, so just use the canonical one for this `IRType`.
+      result = type.getCanonicalLanguageType()
+  }
 
   final IntValue getStartBitOffset() { result = startBitOffset }
 
@@ -85,13 +112,14 @@ class VariableMemoryLocation extends TVariableMemoryLocation, MemoryLocation {
 
   final override string getUniqueId() {
     result = var.getUniqueId() + Interval::getIntervalString(startBitOffset, endBitOffset) + "<" +
-        getTypeIdentityString(type) + ">"
+        type.getIdentityString() + ">"
   }
 
   final override VirtualVariable getVirtualVariable() {
     if variableAddressEscapes(var)
     then result = TUnknownVirtualVariable(var.getEnclosingIRFunction())
-    else result = TVariableMemoryLocation(var, var.getType(), 0, var.getType().getSize() * 8)
+    else
+      result = TVariableMemoryLocation(var, var.getIRType(), _, 0, var.getIRType().getByteSize() * 8)
   }
 
   /**
@@ -99,7 +127,7 @@ class VariableMemoryLocation extends TVariableMemoryLocation, MemoryLocation {
    */
   final predicate coversEntireVariable() {
     startBitOffset = 0 and
-    endBitOffset = var.getType().getSize() * 8
+    endBitOffset = var.getIRType().getByteSize() * 8
   }
 }
 
@@ -111,7 +139,7 @@ class VariableMemoryLocation extends TVariableMemoryLocation, MemoryLocation {
 class VariableVirtualVariable extends VariableMemoryLocation, VirtualVariable {
   VariableVirtualVariable() {
     not variableAddressEscapes(var) and
-    type = var.getType() and
+    type = var.getIRType() and
     coversEntireVariable()
   }
 }
@@ -128,11 +156,33 @@ class UnknownMemoryLocation extends TUnknownMemoryLocation, MemoryLocation {
 
   final override VirtualVariable getVirtualVariable() { result = TUnknownVirtualVariable(irFunc) }
 
-  final override Type getType() { result instanceof UnknownType }
+  final override Language::LanguageType getType() {
+    result = any(IRUnknownType type).getCanonicalLanguageType()
+  }
 
   final override string getUniqueId() { result = "{Unknown}" }
 }
 
+/**
+ * An access to memory that is not known to be confined to a specific `IRVariable`, but is known to
+ * not access memory on the current function's stack frame.
+ */
+class UnknownNonLocalMemoryLocation extends TUnknownNonLocalMemoryLocation, MemoryLocation {
+  IRFunction irFunc;
+
+  UnknownNonLocalMemoryLocation() { this = TUnknownNonLocalMemoryLocation(irFunc) }
+
+  final override string toString() { result = "{UnknownNonLocal}" }
+
+  final override VirtualVariable getVirtualVariable() { result = TUnknownVirtualVariable(irFunc) }
+
+  final override Language::LanguageType getType() {
+    result = any(IRUnknownType type).getCanonicalLanguageType()
+  }
+
+  final override string getUniqueId() { result = "{UnknownNonLocal}" }
+}
+
 /**
  * An access to all aliased memory.
  */
@@ -143,7 +193,9 @@ class UnknownVirtualVariable extends TUnknownVirtualVariable, VirtualVariable {
 
   final override string toString() { result = "{AllAliased}" }
 
-  final override Type getType() { result instanceof UnknownType }
+  final override Language::LanguageType getType() {
+    result = any(IRUnknownType type).getCanonicalLanguageType()
+  }
 
   final override string getUniqueId() { result = " " + toString() }
 
@@ -163,6 +215,13 @@ Overlap getOverlap(MemoryLocation def, MemoryLocation use) {
     def instanceof UnknownMemoryLocation and
     result instanceof MayPartiallyOverlap
     or
+    // An UnknownNonLocalMemoryLocation may partially overlap any location within the same virtual
+    // variable, except a local variable.
+    def.getVirtualVariable() = use.getVirtualVariable() and
+    def instanceof UnknownNonLocalMemoryLocation and
+    result instanceof MayPartiallyOverlap and
+    not use.(VariableMemoryLocation).getVariable() instanceof IRAutomaticVariable
+    or
     exists(VariableMemoryLocation defVariableLocation |
       defVariableLocation = def and
       (
@@ -171,13 +230,20 @@ Overlap getOverlap(MemoryLocation def, MemoryLocation use) {
         (use instanceof UnknownMemoryLocation or use instanceof UnknownVirtualVariable) and
         result instanceof MayPartiallyOverlap
         or
+        // A VariableMemoryLocation that is not a local variable may partially overlap an unknown
+        // non-local location within the same virtual variable.
+        def.getVirtualVariable() = use.getVirtualVariable() and
+        use instanceof UnknownNonLocalMemoryLocation and
+        result instanceof MayPartiallyOverlap and
+        not defVariableLocation.getVariable() instanceof IRAutomaticVariable
+        or
         // A VariableMemoryLocation overlaps another location within the same variable based on the relationship
         // of the two offset intervals.
         exists(Overlap intervalOverlap |
           intervalOverlap = getVariableMemoryLocationOverlap(def, use) and
           if intervalOverlap instanceof MustExactlyOverlap
           then
-            if def.getType() = use.getType()
+            if def.getIRType() = use.getIRType()
             then
               // The def and use types match, so it's an exact overlap.
               result instanceof MustExactlyOverlap
@@ -282,11 +348,11 @@ MemoryLocation getResultMemoryLocation(Instruction instr) {
     (
       (
         kind.usesAddressOperand() and
-        if hasResultMemoryAccess(instr, _, _, _, _)
+        if hasResultMemoryAccess(instr, _, _, _, _, _)
         then
-          exists(IRVariable var, Type type, IntValue startBitOffset, IntValue endBitOffset |
-            hasResultMemoryAccess(instr, var, type, startBitOffset, endBitOffset) and
-            result = TVariableMemoryLocation(var, type, startBitOffset, endBitOffset)
+          exists(IRVariable var, IRType type, IntValue startBitOffset, IntValue endBitOffset |
+            hasResultMemoryAccess(instr, var, type, _, startBitOffset, endBitOffset) and
+            result = TVariableMemoryLocation(var, type, _, startBitOffset, endBitOffset)
           )
         else result = TUnknownMemoryLocation(instr.getEnclosingIRFunction())
       )
@@ -296,6 +362,9 @@ MemoryLocation getResultMemoryLocation(Instruction instr) {
       or
       kind instanceof EscapedMayMemoryAccess and
       result = TUnknownMemoryLocation(instr.getEnclosingIRFunction())
+      or
+      kind instanceof NonLocalMayMemoryAccess and
+      result = TUnknownNonLocalMemoryLocation(instr.getEnclosingIRFunction())
     )
   )
 }
@@ -306,11 +375,11 @@ MemoryLocation getOperandMemoryLocation(MemoryOperand operand) {
     (
       (
         kind.usesAddressOperand() and
-        if hasOperandMemoryAccess(operand, _, _, _, _)
+        if hasOperandMemoryAccess(operand, _, _, _, _, _)
         then
-          exists(IRVariable var, Type type, IntValue startBitOffset, IntValue endBitOffset |
-            hasOperandMemoryAccess(operand, var, type, startBitOffset, endBitOffset) and
-            result = TVariableMemoryLocation(var, type, startBitOffset, endBitOffset)
+          exists(IRVariable var, IRType type, IntValue startBitOffset, IntValue endBitOffset |
+            hasOperandMemoryAccess(operand, var, type, _, startBitOffset, endBitOffset) and
+            result = TVariableMemoryLocation(var, type, _, startBitOffset, endBitOffset)
           )
         else result = TUnknownMemoryLocation(operand.getEnclosingIRFunction())
       )
@@ -320,6 +389,9 @@ MemoryLocation getOperandMemoryLocation(MemoryOperand operand) {
       or
       kind instanceof EscapedMayMemoryAccess and
       result = TUnknownMemoryLocation(operand.getEnclosingIRFunction())
+      or
+      kind instanceof NonLocalMayMemoryAccess and
+      result = TUnknownNonLocalMemoryLocation(operand.getEnclosingIRFunction())
     )
   )
 }

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/IRImports.qll

@@ -1,2 +1,3 @@
 import semmle.code.cpp.ir.implementation.EdgeKind as EdgeKind
+import semmle.code.cpp.ir.implementation.IRType as IRType
 import semmle.code.cpp.ir.implementation.MemoryAccessKind as MemoryAccessKind

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/IRVariableImports.qll

@@ -1,3 +1,4 @@
+import semmle.code.cpp.ir.implementation.IRType as IRType
 import semmle.code.cpp.ir.implementation.TempVariableTag as TempVariableTag
 import semmle.code.cpp.ir.internal.IRUtilities as IRUtilities
 import semmle.code.cpp.ir.internal.TempVariableTag as TTempVariableTag

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/InstructionImports.qll

@@ -1,4 +1,5 @@
 import semmle.code.cpp.ir.implementation.EdgeKind as EdgeKind
+import semmle.code.cpp.ir.implementation.IRType as IRType
 import semmle.code.cpp.ir.implementation.MemoryAccessKind as MemoryAccessKind
 import semmle.code.cpp.ir.implementation.Opcode as Opcode
 import semmle.code.cpp.ir.implementation.internal.OperandTag as OperandTag

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/OperandImports.qll

@@ -1,3 +1,4 @@
 import semmle.code.cpp.ir.implementation.MemoryAccessKind as MemoryAccessKind
+import semmle.code.cpp.ir.implementation.IRType as IRType
 import semmle.code.cpp.ir.internal.Overlap as Overlap
 import semmle.code.cpp.ir.implementation.internal.OperandTag as OperandTag

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/PrintSSA.qll

@@ -4,34 +4,52 @@ private import Alias
 private import SSAConstruction
 private import DebugSSA
 
+bindingset[offset]
+private string getKeySuffixForOffset(int offset) {
+  if offset % 2 = 0 then result = "" else result = "_Chi"
+}
+
+bindingset[offset]
+private int getIndexForOffset(int offset) { result = offset / 2 }
+
 /**
  * Property provide that dumps the memory access of each result. Useful for debugging SSA
  * construction.
  */
 class PropertyProvider extends IRPropertyProvider {
   override string getInstructionProperty(Instruction instruction, string key) {
-    exists(MemoryLocation location |
-      location = getResultMemoryLocation(instruction) and
-      (
-        key = "ResultMemoryLocation" and result = location.toString()
-        or
-        key = "ResultVirtualVariable" and result = location.getVirtualVariable().toString()
+    key = "ResultMemoryLocation" and
+    result = strictconcat(MemoryLocation loc |
+        loc = getResultMemoryLocation(instruction)
+      |
+        loc.toString(), ","
       )
-    )
     or
-    exists(MemoryLocation location |
-      location = getOperandMemoryLocation(instruction.getAnOperand()) and
-      (
-        key = "OperandMemoryAccess" and result = location.toString()
-        or
-        key = "OperandVirtualVariable" and result = location.getVirtualVariable().toString()
+    key = "ResultVirtualVariable" and
+    result = strictconcat(MemoryLocation loc |
+        loc = getResultMemoryLocation(instruction)
+      |
+        loc.getVirtualVariable().toString(), ","
       )
-    )
     or
-    exists(MemoryLocation useLocation, IRBlock defBlock, int defRank, int defIndex |
-      hasDefinitionAtRank(useLocation, _, defBlock, defRank, defIndex) and
-      defBlock.getInstruction(defIndex) = instruction and
-      key = "DefinitionRank[" + useLocation.toString() + "]" and
+    key = "OperandMemoryLocation" and
+    result = strictconcat(MemoryLocation loc |
+        loc = getOperandMemoryLocation(instruction.getAnOperand())
+      |
+        loc.toString(), ","
+      )
+    or
+    key = "OperandVirtualVariable" and
+    result = strictconcat(MemoryLocation loc |
+        loc = getOperandMemoryLocation(instruction.getAnOperand())
+      |
+        loc.getVirtualVariable().toString(), ","
+      )
+    or
+    exists(MemoryLocation useLocation, IRBlock defBlock, int defRank, int defOffset |
+      hasDefinitionAtRank(useLocation, _, defBlock, defRank, defOffset) and
+      defBlock.getInstruction(getIndexForOffset(defOffset)) = instruction and
+      key = "DefinitionRank" + getKeySuffixForOffset(defOffset) + "[" + useLocation.toString() + "]" and
       result = defRank.toString()
     )
     or
@@ -41,10 +59,11 @@ class PropertyProvider extends IRPropertyProvider {
       result = useRank.toString()
     )
     or
-    exists(MemoryLocation useLocation, IRBlock defBlock, int defRank, int defIndex |
-      hasDefinitionAtRank(useLocation, _, defBlock, defRank, defIndex) and
-      defBlock.getInstruction(defIndex) = instruction and
-      key = "DefinitionReachesUse[" + useLocation.toString() + "]" and
+    exists(MemoryLocation useLocation, IRBlock defBlock, int defRank, int defOffset |
+      hasDefinitionAtRank(useLocation, _, defBlock, defRank, defOffset) and
+      defBlock.getInstruction(getIndexForOffset(defOffset)) = instruction and
+      key = "DefinitionReachesUse" + getKeySuffixForOffset(defOffset) + "[" + useLocation.toString()
+          + "]" and
       result = strictconcat(IRBlock useBlock, int useRank, int useIndex |
           exists(Instruction useInstruction |
             hasUseAtRank(useLocation, useBlock, useRank, useInstruction) and

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstruction.qll

@@ -1,8 +1,5 @@
 import SSAConstructionInternal
-private import cpp
-private import semmle.code.cpp.ir.implementation.Opcode
-private import semmle.code.cpp.ir.implementation.internal.OperandTag
-private import semmle.code.cpp.ir.internal.Overlap
+private import SSAConstructionImports
 private import NewIR
 
 private class OldBlock = Reachability::ReachableBlock;
@@ -18,7 +15,7 @@ private module Cached {
   }
 
   cached
-  predicate functionHasIR(Function func) {
+  predicate functionHasIR(Language::Function func) {
     exists(OldIR::IRFunction irFunc | irFunc.getFunction() = func)
   }
 
@@ -42,7 +39,7 @@ private module Cached {
       not oldInstruction instanceof OldIR::PhiInstruction and
       hasChiNode(_, oldInstruction)
     } or
-    Unreached(Function function) {
+    Unreached(Language::Function function) {
       exists(OldInstruction oldInstruction |
         function = oldInstruction.getEnclosingFunction() and
         Reachability::isInfeasibleInstructionSuccessor(oldInstruction, _)
@@ -50,12 +47,14 @@ private module Cached {
     }
 
   cached
-  predicate hasTempVariable(Function func, Locatable ast, TempVariableTag tag, Type type) {
+  predicate hasTempVariable(
+    Language::Function func, Language::AST ast, TempVariableTag tag, Language::LanguageType type
+  ) {
     exists(OldIR::IRTempVariable var |
       var.getEnclosingFunction() = func and
       var.getAST() = ast and
       var.getTag() = tag and
-      var.getType() = type
+      var.getLanguageType() = type
     )
   }
 
@@ -135,24 +134,12 @@ private module Cached {
   }
 
   cached
-  Type getInstructionOperandType(Instruction instr, TypedOperandTag tag) {
+  Language::LanguageType getInstructionOperandType(Instruction instr, TypedOperandTag tag) {
     exists(OldInstruction oldInstruction, OldIR::TypedOperand oldOperand |
       oldInstruction = getOldInstruction(instr) and
       oldOperand = oldInstruction.getAnOperand() and
       tag = oldOperand.getOperandTag() and
-      result = oldOperand.getType()
-    )
-  }
-
-  cached
-  int getInstructionOperandSize(Instruction instr, SideEffectOperandTag tag) {
-    exists(OldInstruction oldInstruction, OldIR::SideEffectOperand oldOperand |
-      oldInstruction = getOldInstruction(instr) and
-      oldOperand = oldInstruction.getAnOperand() and
-      tag = oldOperand.getOperandTag() and
-      // Only return a result for operands that need an explicit result size.
-      oldOperand.getType() instanceof UnknownType and
-      result = oldOperand.getSize()
+      result = oldOperand.getLanguageType()
     )
   }
 
@@ -196,20 +183,21 @@ private module Cached {
   }
 
   cached
-  Expr getInstructionConvertedResultExpression(Instruction instruction) {
+  Language::Expr getInstructionConvertedResultExpression(Instruction instruction) {
     result = getOldInstruction(instruction).getConvertedResultExpression()
   }
 
   cached
-  Expr getInstructionUnconvertedResultExpression(Instruction instruction) {
+  Language::Expr getInstructionUnconvertedResultExpression(Instruction instruction) {
     result = getOldInstruction(instruction).getUnconvertedResultExpression()
   }
 
-  /**
+  /*
    * This adds Chi nodes to the instruction successor relation; if an instruction has a Chi node,
    * that node is its successor in the new successor relation, and the Chi node's successors are
    * the new instructions generated from the successors of the old instruction
    */
+
   cached
   Instruction getInstructionSuccessor(Instruction instruction, EdgeKind kind) {
     if hasChiNode(_, getOldInstruction(instruction))
@@ -252,7 +240,7 @@ private module Cached {
   }
 
   cached
-  Locatable getInstructionAST(Instruction instruction) {
+  Language::AST getInstructionAST(Instruction instruction) {
     exists(OldInstruction oldInstruction |
       instruction = WrappedInstruction(oldInstruction)
       or
@@ -270,29 +258,25 @@ private module Cached {
   }
 
   cached
-  predicate instructionHasType(Instruction instruction, Type type, boolean isGLValue) {
+  Language::LanguageType getInstructionResultType(Instruction instruction) {
     exists(OldInstruction oldInstruction |
       instruction = WrappedInstruction(oldInstruction) and
-      type = oldInstruction.getResultType() and
-      if oldInstruction.isGLValue() then isGLValue = true else isGLValue = false
+      result = oldInstruction.getResultLanguageType()
     )
     or
     exists(OldInstruction oldInstruction, Alias::VirtualVariable vvar |
       instruction = Chi(oldInstruction) and
       hasChiNode(vvar, oldInstruction) and
-      type = vvar.getType() and
-      isGLValue = false
+      result = vvar.getType()
     )
     or
     exists(Alias::MemoryLocation location |
       instruction = Phi(_, location) and
-      type = location.getType() and
-      isGLValue = false
+      result = location.getType()
     )
     or
     instruction = Unreached(_) and
-    type instanceof VoidType and
-    isGLValue = false
+    result = Language::getVoidType()
   }
 
   cached
@@ -334,11 +318,11 @@ private module Cached {
   IRVariable getInstructionVariable(Instruction instruction) {
     result = getNewIRVariable(getOldInstruction(instruction)
             .(OldIR::VariableInstruction)
-            .getVariable())
+            .getIRVariable())
   }
 
   cached
-  Field getInstructionField(Instruction instruction) {
+  Language::Field getInstructionField(Instruction instruction) {
     result = getOldInstruction(instruction).(OldIR::FieldInstruction).getField()
   }
 
@@ -348,7 +332,7 @@ private module Cached {
   }
 
   cached
-  Function getInstructionFunction(Instruction instruction) {
+  Language::Function getInstructionFunction(Instruction instruction) {
     result = getOldInstruction(instruction).(OldIR::FunctionInstruction).getFunctionSymbol()
   }
 
@@ -358,19 +342,19 @@ private module Cached {
   }
 
   cached
-  StringLiteral getInstructionStringLiteral(Instruction instruction) {
+  Language::StringLiteral getInstructionStringLiteral(Instruction instruction) {
     result = getOldInstruction(instruction).(OldIR::StringConstantInstruction).getValue()
   }
 
   cached
-  BuiltInOperation getInstructionBuiltInOperation(Instruction instruction) {
+  Language::BuiltInOperation getInstructionBuiltInOperation(Instruction instruction) {
     result = getOldInstruction(instruction)
           .(OldIR::BuiltInOperationInstruction)
           .getBuiltInOperation()
   }
 
   cached
-  Type getInstructionExceptionType(Instruction instruction) {
+  Language::LanguageType getInstructionExceptionType(Instruction instruction) {
     result = getOldInstruction(instruction).(OldIR::CatchByTypeInstruction).getExceptionType()
   }
 
@@ -380,14 +364,9 @@ private module Cached {
   }
 
   cached
-  int getInstructionResultSize(Instruction instruction) {
-    // Only return a result for instructions that needed an explicit result size.
-    instruction.getResultType() instanceof UnknownType and
-    result = getOldInstruction(instruction).getResultSize()
-  }
-
-  cached
-  predicate getInstructionInheritance(Instruction instruction, Class baseClass, Class derivedClass) {
+  predicate getInstructionInheritance(
+    Instruction instruction, Language::Class baseClass, Language::Class derivedClass
+  ) {
     exists(OldIR::InheritanceConversionInstruction oldInstr |
       oldInstr = getOldInstruction(instruction) and
       baseClass = oldInstr.getBaseClass() and

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstructionImports.qll

@@ -0,0 +1,3 @@
+import semmle.code.cpp.ir.implementation.Opcode
+import semmle.code.cpp.ir.implementation.internal.OperandTag
+import semmle.code.cpp.ir.internal.Overlap