Fix bad joins on function names and unnecessarily large relation on integer constant macros

Author: MichaelRFairhurst

c/cert/src/rules/DCL40-C/IncompatibleFunctionDeclarations.ql

@@ -24,28 +24,32 @@ import codingstandards.c.cert
 import codingstandards.cpp.types.Compatible
 import ExternalIdentifiers
 
-predicate interestedInFunctions(FunctionDeclarationEntry f1, FunctionDeclarationEntry f2) {
+predicate interestedInFunctions(
+  FunctionDeclarationEntry f1, FunctionDeclarationEntry f2, ExternalIdentifiers d
+) {
   not f1 = f2 and
-  f1.getDeclaration() = f2.getDeclaration() and
-  f1.getName() = f2.getName()
+  d = f1.getDeclaration() and
+  d = f2.getDeclaration()
+}
+
+predicate interestedInFunctions(FunctionDeclarationEntry f1, FunctionDeclarationEntry f2) {
+  interestedInFunctions(f1, f2, _)
 }
 
+module FuncDeclEquiv =
+  FunctionDeclarationTypeEquivalence<TypesCompatibleConfig, interestedInFunctions/2>;
+
 from ExternalIdentifiers d, FunctionDeclarationEntry f1, FunctionDeclarationEntry f2
 where
   not isExcluded(f1, Declarations2Package::incompatibleFunctionDeclarationsQuery()) and
   not isExcluded(f2, Declarations2Package::incompatibleFunctionDeclarationsQuery()) and
-  not f1 = f2 and
-  f1.getDeclaration() = d and
-  f2.getDeclaration() = d and
-  f1.getName() = f2.getName() and
+  interestedInFunctions(f1, f2, d) and
   (
     //return type check
-    not FunctionDeclarationTypeEquivalence<TypesCompatibleConfig, interestedInFunctions/2>::equalReturnTypes(f1,
-      f2)
+    not FuncDeclEquiv::equalReturnTypes(f1, f2)
     or
     //parameter type check
-    not FunctionDeclarationTypeEquivalence<TypesCompatibleConfig, interestedInFunctions/2>::equalParameterTypes(f1,
-      f2)
+    not FuncDeclEquiv::equalParameterTypes(f1, f2)
   ) and
   // Apply ordering on start line, trying to avoid the optimiser applying this join too early
   // in the pipeline

c/misra/src/rules/RULE-7-5/IncorrectlySizedIntegerConstantMacroArgument.ql

@@ -20,6 +20,7 @@ predicate matchesSign(IntegerConstantMacro macro, PossiblyNegativeLiteral litera
   literal.isNegative() implies macro.isSigned()
 }
 
+bindingset[literal]
 predicate matchesSize(IntegerConstantMacro macro, PossiblyNegativeLiteral literal) {
   literal.getRawValue() <= macro.maxValue() and
   literal.getRawValue() >= macro.minValue()

c/misra/src/rules/RULE-8-4/CompatibleDeclarationFunctionDefined.ql

@@ -23,13 +23,14 @@ predicate interestedInFunctions(FunctionDeclarationEntry f1, FunctionDeclaration
   f1.getDeclaration() instanceof ExternalIdentifiers and
   f1.isDefinition() and
   f1.getDeclaration() = f2.getDeclaration() and
-  // This condition should always hold, but removing it affects join order performance.
-  f1.getName() = f2.getName() and
   not f2.isDefinition() and
   not f1.isFromTemplateInstantiation(_) and
   not f2.isFromTemplateInstantiation(_)
 }
 
+module FunDeclEquiv =
+  FunctionDeclarationTypeEquivalence<TypesCompatibleConfig, interestedInFunctions/2>;
+
 from FunctionDeclarationEntry f1
 where
   not isExcluded(f1, Declarations4Package::compatibleDeclarationFunctionDefinedQuery()) and
@@ -44,17 +45,13 @@ where
     or
     //or one exists that is close but incompatible in some way
     exists(FunctionDeclarationEntry f2 |
-      f1.getName() = f2.getName() and
-      not f2.isDefinition() and
-      f2.getDeclaration() = f1.getDeclaration() and
+      interestedInFunctions(f1, f2) and
       (
         //return types differ
-        not FunctionDeclarationTypeEquivalence<TypesCompatibleConfig, interestedInFunctions/2>::equalReturnTypes(f1,
-          f2)
+        not FunDeclEquiv::equalReturnTypes(f1, f2)
         or
         //parameter types differ
-        not FunctionDeclarationTypeEquivalence<TypesCompatibleConfig, interestedInFunctions/2>::equalParameterTypes(f1,
-          f2)
+        not FunDeclEquiv::equalParameterTypes(f1, f2)
         or
         //parameter names differ
         parameterNamesUnmatched(f1, f2)

change_notes/2025-7-15-fix-performance-issues-in-2.20.7.md

@@ -0,0 +1,4 @@
+ - `DCL40-C`, `RULE-8-4`: `IncompatibleFunctionDeclarations.ql`, `CompatibleDeclarationFunctionDefined.ql`.
+   - Fixed performance issues introduced when upgrading to CodeQL `2.20.7` by removing unnecessary check that matching function declarations have matching names.
+ - `RULE-7-5`: `IncorrectlySizedIntegerConstantMacroArgument.ql`.
+   - Added a `bindingset` to improve performance when checking if a literal matches the size of an integer constant macro.