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Merge pull request #2434 from felicitymay/1.23/SD-4095-finalize-change-notes-cpp

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1.23: SD-4095 finalize change notes for C/C++
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Jonas Jensen
2019-11-26 18:56:22 +01:00
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change-notes/1.23/analysis-cpp.md
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The following changes in version 1.23 affect C/C++ analysis in all applications.
## General improvements
## New queries
| **Query** | **Tags** | **Purpose** |
|-----------------------------|-----------|--------------------------------------------------------------------|
| Hard-coded Japanese era start date (`cpp/japanese-era/exact-era-date`) | reliability, japanese-era | This query is a combination of two old queries that were identical in purpose but separate as an implementation detail. This new query replaces Hard-coded Japanese era start date in call (`cpp/japanese-era/constructor-or-method-with-exact-era-date`) and Hard-coded Japanese era start date in struct (`cpp/japanese-era/struct-with-exact-era-date`). |
| Signed overflow check (`cpp/signed-overflow-check`) | correctness, security | Finds overflow checks that rely on signed integer addition to overflow, which has undefined behavior. Example: `a + b < a`. |
| Pointer overflow check (`cpp/pointer-overflow-check`) | correctness, security | Finds overflow checks that rely on pointer addition to overflow, which has undefined behavior. Example: `ptr + a < ptr`. |
| Hard-coded Japanese era start date (`cpp/japanese-era/exact-era-date`) | reliability, japanese-era | This query is a combination of two old queries that were identical in purpose but separate as an implementation detail. This new query replaces Hard-coded Japanese era start date in call (`cpp/japanese-era/constructor-or-method-with-exact-era-date`) and Hard-coded Japanese era start date in struct (`cpp/japanese-era/struct-with-exact-era-date`). Results are not shown on LGTM by default. |
| Pointer overflow check (`cpp/pointer-overflow-check`) | correctness, security | Finds overflow checks that rely on pointer addition to overflow, which has undefined behavior. Example: `ptr + a < ptr`. Results are shown on LGTM by default. |
| Signed overflow check (`cpp/signed-overflow-check`) | correctness, security | Finds overflow checks that rely on signed integer addition to overflow, which has undefined behavior. Example: `a + b < a`. Results are shown on LGTM by default. |
## Changes to existing queries
| **Query** | **Expected impact** | **Change** |
|----------------------------|------------------------|------------------------------------------------------------------|
| Query name (`query id`) | Expected impact | Message. |
| 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. |
| 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). |
| Non-constant format string (`cpp/non-constant-format`) | Fewer false positive results | Fixed false positive results triggrered by mismatching declarations of a formatting function. |
| 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. |
| Non-constant format string (`cpp/non-constant-format`) | Fewer false positive results | Fixed false positives resulting from mistmatching declarations of a formatting function. |
| Wrong type of arguments to formatting function (`cpp/wrong-type-format-argument`) | More correct results and fewer false positive results | This query now understands explicitly specified argument numbers in format strings, such as the `1$` in `%1$s`. |
| Too few arguments to formatting function (`cpp/wrong-number-format-arguments`) | Fewer false positive results | Fixed false positive results triggered by mismatching declarations of a formatting function. |
| Too many arguments to formatting function (`cpp/too-many-format-arguments`) | Fewer false positive results | Fixed false positive results triggered by mismatching declarations of a formatting function. |
| Unclear comparison precedence (`cpp/comparison-precedence`) | Fewer false positive results | False positive results involving template classes and functions have been fixed. |
| Wrong type of arguments to formatting function (`cpp/wrong-type-format-argument`) | More correct results and fewer false positive results | This query now understands explicitly-specified argument numbers in format strings, such as the `1$` in `%1$s`. |
## Changes to libraries
* The data-flow library in `semmle.code.cpp.dataflow.DataFlow` and
`semmle.code.cpp.dataflow.TaintTracking` have had extensive changes:
* Data flow through fields is now more complete and reliable.
* To debug a lack of flow, instead of specifying `isSink(Node n) { any() }`
on a configuration to
explore the possible flow from a source, it is recommended to use the new
`Configuration::hasPartialFlow` predicate as this gives a more complete
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 has been extended with a new feature to aid debugging.
Previously, to explore the possible flow from all sources you could specify `isSink(Node n) { any() }` on a configuration.
Now you can use the new `Configuration::hasPartialFlow` predicate,
which gives a more complete picture of the partial flow paths from a given source, including flow that doesn't reach any sink.
The feature is disabled by default and can be enabled for individual configurations by overriding `int explorationLimit()`.
* There is now flow out of C++ reference parameters.
* There is now flow through the address-of operator (`&`).
* The `DataFlow::DefinitionByReferenceNode` class now considers `f(x)` to be a
@@ -54,17 +50,17 @@ The following changes in version 1.23 affect C/C++ analysis in all applications.
`TaintTracking::localExprTaint` predicate to make it easy to use the most
common case of local data flow and taint: from one `Expr` to another.
* The member predicates of the `FunctionInput` and `FunctionOutput` classes have been renamed for
clarity (e.g. `isOutReturnPointer()` to `isReturnValueDeref()`). The existing member predicates
clarity (for example, `isOutReturnPointer()` to `isReturnValueDeref()`). The existing member predicates
have been deprecated, and will be removed in a future release. Code that uses the old member
predicates should be updated to use the corresponding new member predicate.
* The predicate `Declaration.hasGlobalOrStdName` has been added, making it
easier to recognize C library functions called from C++.
* 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
lead to changes 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.
`Declaration::getATemplateArgument` have changed to `Locatable`. For details, see the
CodeQL library documentation for `Declaration::getTemplateArgument()` and
`Declaration::getTemplateArgumentKind()`.