Address review comments

Author: knewbury01

change_notes/2026-03-27-update-compatible-objects-DCL40-C.md

@@ -1,2 +1,2 @@
  - `DCL40-C` - `IncompatibleObjectDeclarations.ql`:
-   - Enhanced the query's ability to compare objects with array type, which will reduce false positives.
+   - The rule now is capable to detect equivalence based on compatible types instead of exact types (which was what it was previously checking on objects). This will eliminate false positives for some array types and types using equivalent typedefs.

cpp/common/src/codingstandards/cpp/rules/incompatibleobjectdeclaration/IncompatibleObjectDeclaration.qll

@@ -15,8 +15,12 @@ signature module IncompatibleObjectDeclarationConfigSig {
   Query getQuery();
 }
 
+class VariableDeclarationEntryExternal extends VariableDeclarationEntry {
+  VariableDeclarationEntryExternal() { this.getDeclaration() instanceof ExternalIdentifiers }
+}
+
 predicate relevantTypes(Type a, Type b) {
-  exists(VariableDeclarationEntry varA, VariableDeclarationEntry varB |
+  exists(VariableDeclarationEntryExternal varA, VariableDeclarationEntryExternal varB |
     not varA = varB and
     varA.getVariable().getName() = varB.getVariable().getName() and
     a = varA.getType() and
@@ -26,16 +30,14 @@ predicate relevantTypes(Type a, Type b) {
 
 module IncompatibleObjectDeclaration<IncompatibleObjectDeclarationConfigSig Config> {
   query predicate problems(
-    VariableDeclarationEntry decl1, string message, VariableDeclarationEntry decl2,
+    VariableDeclarationEntryExternal decl1, string message, VariableDeclarationEntryExternal decl2,
     string secondMessage
   ) {
     not isExcluded(decl1, Config::getQuery()) and
     not isExcluded(decl2, Config::getQuery()) and
     not TypeEquivalence<TypesCompatibleConfig, relevantTypes/2>::equalTypes(decl1.getType(),
       decl2.getType()) and
     not decl1 = decl2 and
-    decl1.getDeclaration() instanceof ExternalIdentifiers and
-    decl2.getDeclaration() instanceof ExternalIdentifiers and
     decl1.getLocation().getStartLine() >= decl2.getLocation().getStartLine() and
     decl1.getVariable().getName() = decl2.getVariable().getName() and
     secondMessage = decl2.getName() and

cpp/common/test/rules/incompatibleobjectdeclaration/IncompatibleObjectDeclaration.expected

@@ -1,4 +1,6 @@
 | test1.cpp:1:12:1:12 | declaration of i | The object is not compatible with a re-declaration $@. | test.cpp:1:7:1:7 | definition of i | i |
 | test1.cpp:2:13:2:13 | declaration of a | The object is not compatible with a re-declaration $@. | test.cpp:2:5:2:5 | definition of a | a |
+| test1.cpp:9:18:9:18 | declaration of x | The object is not compatible with a re-declaration $@. | test.cpp:8:17:8:17 | declaration of x | x |
+| test1.cpp:11:10:11:11 | declaration of a1 | The object is not compatible with a re-declaration $@. | test.cpp:10:10:10:11 | declaration of a1 | a1 |
 | test.cpp:1:7:1:7 | definition of i | The object is not compatible with a re-declaration $@. | test1.cpp:1:12:1:12 | declaration of i | i |
 | test.cpp:2:5:2:5 | definition of a | The object is not compatible with a re-declaration $@. | test1.cpp:2:13:2:13 | declaration of a | a |

cpp/common/test/rules/incompatibleobjectdeclaration/test.cpp

@@ -2,4 +2,9 @@ short i;                // NON_COMPLIANT
 int a[] = {1, 2, 3, 4}; // NON_COMPLIANT
 long b; // NON_COMPLIANT[FALSE_NEGATIVE] -- compiler does not extract c linkage
 extern int c[]; // COMPLIANT
-extern int d;   // COMPLIANT
+extern int d;   // COMPLIANT
+
+#include "test.h"
+extern C<int[]> x; // NON_COMPLIANT
+
+extern B a1; // NON_COMPLIANT

cpp/common/test/rules/incompatibleobjectdeclaration/test.h

@@ -0,0 +1,5 @@
+
+template <typename T> class C {};
+
+class A {};
+class B {};

cpp/common/test/rules/incompatibleobjectdeclaration/test1.cpp

@@ -3,4 +3,9 @@ extern int *a; // NON_COMPLIANT
 extern "C" long
     b; // NON_COMPLIANT[FALSE_NEGATIVE] -- compiler does not extract c linkage
 extern int c[1]; // COMPLIANT
-extern int d{1}; // COMPLIANT
+extern int d{1}; // COMPLIANT
+
+#include "test.h"
+extern C<int[4]> x; // NON_COMPLIANT
+
+extern A a1; // NON_COMPLIANT