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fix #13272: false positive: unusedFunction (function attributes) #7176

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merged 5 commits into from
Jan 7, 2025
Merged

fix #13272: false positive: unusedFunction (function attributes) #7176

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163ae86
add test
ludviggunne Jan 4, 2025
34a2277
fix #13272
ludviggunne Jan 4, 2025
14b4416
fix warning
ludviggunne Jan 4, 2025
8256294
properly check language standard
ludviggunne Jan 5, 2025
ecaae07
use short circuit, remove redundant match
ludviggunne Jan 5, 2025
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3 changes: 3 additions & 0 deletions lib/checkunusedfunctions.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,9 @@ void CheckUnusedFunctions::parseTokens(const Tokenizer &tokenizer, const Setting
if (func->isAttributeConstructor() || func->isAttributeDestructor() || func->type != Function::eFunction || func->isOperator())
continue;

if (func->isAttributeUnused() || func->isAttributeMaybeUnused())
continue;

if (func->isExtern())
continue;

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6 changes: 6 additions & 0 deletions lib/symboldatabase.h
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Expand Up @@ -819,6 +819,12 @@ class CPPCHECKLIB Function {
bool isAttributeNodiscard() const {
return tokenDef->isAttributeNodiscard();
}
bool isAttributeUnused() const {
return tokenDef->isAttributeUnused();
}
bool isAttributeMaybeUnused() const {
return tokenDef->isAttributeMaybeUnused();
}

bool hasBody() const {
return getFlag(fHasBody);
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10 changes: 9 additions & 1 deletion lib/tokenize.cpp
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Expand Up @@ -9382,6 +9382,8 @@ void Tokenizer::simplifyCPPAttribute()
// According to cppreference alignas is a c21 feature however the macro is often available when compiling c11
const bool hasAlignas = ((isCPP() && mSettings.standards.cpp >= Standards::CPP11) || (isC() && mSettings.standards.c >= Standards::C11));
const bool hasCppAttribute = ((isCPP() && mSettings.standards.cpp >= Standards::CPP11) || (isC() && mSettings.standards.c >= Standards::C23));
const bool hasMaybeUnused =((isCPP() && mSettings.standards.cpp >= Standards::CPP17) || (isC() && mSettings.standards.c >= Standards::C23));
const bool hasMaybeUnusedUnderscores = (isC() && mSettings.standards.c >= Standards::C23);

if (!hasAlignas && !hasCppAttribute)
return;
Expand Down Expand Up @@ -9414,11 +9416,17 @@ void Tokenizer::simplifyCPPAttribute()
if (head && head->str() == "(" && isFunctionHead(head, "{|;")) {
head->previous()->isAttributeNodiscard(true);
}
} else if (Token::findsimplematch(tok->tokAt(2), "maybe_unused", tok->link())) {
} else if ((hasMaybeUnusedUnderscores && Token::findsimplematch(tok->tokAt(2), "__maybe_unused__", tok->link()))
|| (hasMaybeUnused && Token::findsimplematch(tok->tokAt(2), "maybe_unused", tok->link()))) {
Token* head = skipCPPOrAlignAttribute(tok)->next();
while (isCPPAttribute(head) || isAlignAttribute(head))
head = skipCPPOrAlignAttribute(head)->next();
head->isAttributeMaybeUnused(true);
} else if (Token::findsimplematch(tok->tokAt(2), "unused", tok->link())) {
Token* head = skipCPPOrAlignAttribute(tok)->next();
while (isCPPAttribute(head) || isAlignAttribute(head))
head = skipCPPOrAlignAttribute(head)->next();
head->isAttributeUnused(true);
} else if (Token::Match(tok->previous(), ") [ [ expects|ensures|assert default|audit|axiom| : %name% <|<=|>|>= %num% ] ]")) {
const Token *vartok = tok->tokAt(4);
if (vartok->str() == ":")
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30 changes: 28 additions & 2 deletions test/testunusedfunctions.cpp
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Expand Up @@ -86,16 +86,18 @@ class TestUnusedFunctions : public TestFixture {
TEST_CASE(parensInit);
TEST_CASE(typeInCast);
TEST_CASE(attributeCleanup);
TEST_CASE(attributeUnused);
TEST_CASE(attributeMaybeUnused);
}

#define check(...) check_(__FILE__, __LINE__, __VA_ARGS__)
template<size_t size>
void check_(const char* file, int line, const char (&code)[size], Platform::Type platform = Platform::Type::Native, const Settings *s = nullptr) {
void check_(const char* file, int line, const char (&code)[size], Platform::Type platform = Platform::Type::Native, const Settings *s = nullptr, bool cpp = true) {
const Settings settings1 = settingsBuilder(s ? *s : settings).platform(platform).build();

// Tokenize..
SimpleTokenizer tokenizer(settings1, *this);
ASSERT_LOC(tokenizer.tokenize(code), file, line);
ASSERT_LOC(tokenizer.tokenize(code, cpp), file, line);

// Check for unused functions..
CheckUnusedFunctions checkUnusedFunctions;
Expand Down Expand Up @@ -794,6 +796,30 @@ class TestUnusedFunctions : public TestFixture {
"}\n");
ASSERT_EQUALS("", errout_str());
}

void attributeUnused()
{
check("[[unused]] void f() {}\n");
ASSERT_EQUALS("", errout_str());

check("[[gnu::unused]] void f() {}\n");
ASSERT_EQUALS("", errout_str());

check("__attribute__((unused)) void f() {}\n");
ASSERT_EQUALS("", errout_str());
}

void attributeMaybeUnused()
{
check("[[__maybe_unused__]] void f() {}\n", Platform::Type::Native, nullptr, false);
ASSERT_EQUALS("", errout_str());

check("[[maybe_unused]] void f() {}\n", Platform::Type::Native, nullptr, false);
ASSERT_EQUALS("", errout_str());

check("[[maybe_unused]] void f() {}\n");
ASSERT_EQUALS("", errout_str());
}
};

REGISTER_TEST(TestUnusedFunctions)
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