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Fix #14125: false positive: unusedVariable with trailing [[maybe_unused]] attribute #8029

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Fix #14125: false positive: unusedVariable with trailing [[maybe_unused]] attribute #8029

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110ba00
Add tests
ludviggunne Dec 12, 2025
fb80be8
Fix #14125
ludviggunne Dec 12, 2025
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36 changes: 25 additions & 11 deletions lib/tokenize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9593,19 +9593,33 @@ void Tokenizer::simplifyCPPAttribute()
if (!head)
syntaxError(tok);

while (Token::Match(head->next(), "%name%|*|&|&&|const|static|inline|volatile"))
head = head->next();
if (Token::Match(head, "%name%") && !Token::Match(head, "auto ["))
head->isAttributeMaybeUnused(true);
else if (Token::Match(tok->previous(), "%name%") && Token::Match(tok->link(), "] [;={]")) {
tok->previous()->isAttributeMaybeUnused(true);
if (Token::simpleMatch(head, ";")) {
Token *backTok = tok;
while (backTok && !Token::Match(backTok, "%name%")) {
if (Token::Match(backTok, "]|)"))
backTok = backTok->link();
backTok = backTok->previous();
if (Token::Match(backTok, "[;{}]"))
backTok = nullptr;
}
if (backTok) {
backTok->isAttributeMaybeUnused(true);
}
} else {
if (Token::simpleMatch(head->next(), "[")) {
while (Token::Match(head->next(), "%name%|::|*|&|&&|const|static|inline|volatile"))
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@danmar danmar Dec 19, 2025

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As far as I understand, this expression

                    while (Token::Match(head->next(), "%name%|::|*|&|&&|const|static|inline|volatile"))

works the same as this expression?

                    while (Token::Match(head->next(), "%name%|::|*|&|&&"))

or am I wrong?

head = head->next();
const Token *end = head->link();
for (head = head->next(); end && head != end; head = head->next()) {
if (Token::Match(head, "%name%")) {
head->isAttributeMaybeUnused(true);
if (Token::Match(head, "%name%") && !Token::Match(head, "auto ["))
head->isAttributeMaybeUnused(true);
else if (Token::Match(tok->previous(), "%name%") && Token::Match(tok->link(), "] [;={]")) {
tok->previous()->isAttributeMaybeUnused(true);
} else {
if (Token::simpleMatch(head->next(), "[")) {
head = head->next();
const Token *end = head->link();
for (head = head->next(); end && head != end; head = head->next()) {
if (Token::Match(head, "%name%")) {
head->isAttributeMaybeUnused(true);
}
}
}
}
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18 changes: 16 additions & 2 deletions test/testtokenize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -276,7 +276,8 @@ class TestTokenizer : public TestFixture {
TEST_CASE(functionAttributeListAfter);
TEST_CASE(functionAttributeListAfter2);
TEST_CASE(cppMaybeUnusedBefore);
TEST_CASE(cppMaybeUnusedAfter);
TEST_CASE(cppMaybeUnusedAfter1);
TEST_CASE(cppMaybeUnusedAfter2);
TEST_CASE(cppMaybeUnusedStructuredBinding);

TEST_CASE(splitTemplateRightAngleBrackets);
Expand Down Expand Up @@ -4258,7 +4259,7 @@ class TestTokenizer : public TestFixture {
ASSERT(var && var->isAttributeMaybeUnused());
}

void cppMaybeUnusedAfter() {
void cppMaybeUnusedAfter1() {
const char code[] = "int var [[maybe_unused]] {};";
const char expected[] = "int var { } ;";

Expand All @@ -4271,6 +4272,19 @@ class TestTokenizer : public TestFixture {
ASSERT(var && var->isAttributeMaybeUnused());
}

void cppMaybeUnusedAfter2() {
const char code[] = "std::string var [[maybe_unused]];";
const char expected[] = "std :: string var ;";

SimpleTokenizer tokenizer(settings0, *this);
ASSERT(tokenizer.tokenize(code));

ASSERT_EQUALS(expected, tokenizer.tokens()->stringifyList(nullptr, false));

const Token *var = Token::findsimplematch(tokenizer.tokens(), "var");
ASSERT(var && var->isAttributeMaybeUnused());
}

void cppMaybeUnusedStructuredBinding() {
const char code[] = "[[maybe_unused]] auto [var1, var2] = f();";
const char expected[] = "auto [ var1 , var2 ] = f ( ) ;";
Expand Down
6 changes: 6 additions & 0 deletions test/testunusedvar.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6531,6 +6531,12 @@ class TestUnusedVar : public TestFixture {
" [[maybe_unused]] char b[1][2];\n"
"}");
ASSERT_EQUALS("", errout_str());

functionVariableUsage("int main() {\n"
" std::string a [[maybe_unused]];\n"
" f();\n"
"}");
ASSERT_EQUALS("", errout_str());
}

void localvarrvalue() { // ticket #13977
Expand Down
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