Merge pull request #9971 from jketema/attribute-arg

C++: Handle all forms of constant attribute arguments

cpp/downgrades/34549c3b0937002f11037d01822ebe99442c1402/attribute_args.ql

@@ -0,0 +1,17 @@
+class AttributeArgument extends @attribute_arg {
+  string toString() { none() }
+}
+
+class Attribute extends @attribute {
+  string toString() { none() }
+}
+
+class LocationDefault extends @location_default {
+  string toString() { none() }
+}
+
+from AttributeArgument arg, int kind, Attribute attr, int index, LocationDefault location
+where
+  attribute_args(arg, kind, attr, index, location) and
+  not arg instanceof @attribute_arg_constant_expr
+select arg, kind, attr, index, location

cpp/downgrades/34549c3b0937002f11037d01822ebe99442c1402/upgrade.properties

@@ -0,0 +1,4 @@
+description: Support all constant attribute arguments
+compatibility: backwards
+attribute_arg_constant.rel: delete
+attribute_args.rel: run attribute_args.qlo

cpp/ql/lib/change-notes/2022-08-10-constant-attribute-argument-support.md

@@ -0,0 +1,4 @@
+---
+category: feature
+---
+* Added a predicate `getValueConstant` to `AttributeArgument` that yields the argument value as an `Expr` when the value is a constant expression.

cpp/ql/lib/semmle/code/cpp/Specifier.qll

@@ -12,7 +12,7 @@ private import semmle.code.cpp.internal.ResolveClass
 class Specifier extends Element, @specifier {
   /** Gets a dummy location for the specifier. */
   override Location getLocation() {
-    suppressUnusedThis(this) and
+    exists(this) and
     result instanceof UnknownDefaultLocation
   }
 
@@ -256,9 +256,13 @@ class AttributeArgument extends Element, @attribute_arg {
 
   /**
    * Gets the text for the value of this argument, if its value is
-   * a string or a number.
+   * a constant or token.
    */
-  string getValueText() { attribute_arg_value(underlyingElement(this), result) }
+  string getValueText() {
+    if underlyingElement(this) instanceof @attribute_arg_constant_expr
+    then result = this.getValueConstant().getValue()
+    else attribute_arg_value(underlyingElement(this), result)
+  }
 
   /**
    * Gets the value of this argument, if its value is integral.
@@ -270,6 +274,13 @@ class AttributeArgument extends Element, @attribute_arg {
    */
   Type getValueType() { attribute_arg_type(underlyingElement(this), unresolveElement(result)) }
 
+  /**
+   * Gets the value of this argument, if its value is a constant.
+   */
+  Expr getValueConstant() {
+    attribute_arg_constant(underlyingElement(this), unresolveElement(result))
+  }
+
   /**
    * Gets the attribute to which this is an argument.
    */
@@ -294,11 +305,12 @@ class AttributeArgument extends Element, @attribute_arg {
         (
           if underlyingElement(this) instanceof @attribute_arg_type
           then tail = this.getValueType().getName()
-          else tail = this.getValueText()
+          else
+            if underlyingElement(this) instanceof @attribute_arg_constant_expr
+            then tail = this.getValueConstant().toString()
+            else tail = this.getValueText()
         ) and
         result = prefix + tail
       )
   }
 }
-
-private predicate suppressUnusedThis(Specifier s) { any() }

cpp/ql/lib/semmlecode.cpp.dbscheme

@@ -899,6 +899,7 @@ case @attribute_arg.kind of
 | 1 = @attribute_arg_token
 | 2 = @attribute_arg_constant
 | 3 = @attribute_arg_type
+| 4 = @attribute_arg_constant_expr
 ;
 
 attribute_arg_value(
@@ -909,6 +910,10 @@ attribute_arg_type(
     unique int arg: @attribute_arg ref,
     int type_id: @type ref
 );
+attribute_arg_constant(
+    unique int arg: @attribute_arg ref,
+    int constant: @expr ref
+)
 attribute_arg_name(
     unique int arg: @attribute_arg ref,
     string name: string ref

cpp/ql/lib/upgrades/23f7cbb88a4eb29f30c3490363dc201bc054c5ff/upgrade.properties

@@ -0,0 +1,2 @@
+description: Support all constant attribute arguments
+compatibility: partial

cpp/ql/test/library-tests/constants/strlen/expr.expected

@@ -1,3 +1,4 @@
+| strlen.cpp:7:49:7:49 | 1 |
 | strlen.cpp:11:39:11:48 | array to pointer conversion |
 | strlen.cpp:11:39:11:48 | file.ext |
 | strlen.cpp:12:35:12:40 | call to strlen |