Check isAttributeUnused()

Author: chrchr-github

Diff for: lib/checkunusedfunctions.cpp

@@ -98,7 +98,7 @@ void CheckUnusedFunctions::parseTokens(const Tokenizer &tokenizer, const Setting
 
             FunctionUsage &usage = mFunctions[stripTemplateParameters(func->name())];
 
-            if (func->retDef && func->retDef->isAttributeMaybeUnused()) {
+            if (func->retDef && (func->retDef->isAttributeUnused() || func->retDef->isAttributeMaybeUnused())) {
                 usage.usedOtherFile = true;
             }
 

Diff for: test/testunusedfunctions.cpp

@@ -502,7 +502,8 @@ class TestUnusedFunctions : public TestFixture {
         check("extern \"C\" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t dataSize) { return 0; }\n");
         ASSERT_EQUALS("", errout_str());
 
-        check("[[maybe_unused]] void f() {}"); // #13268
+        check("[[maybe_unused]] void f() {}\n"); // #13268
+              "__attribute__((unused)) void g() {}\n";
         ASSERT_EQUALS("", errout_str());
     }