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

Author: ludviggunne

lib/tokenize.cpp

@@ -9607,17 +9607,27 @@ 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 (Token::Match(backTok, "]|[|)")) {
+                        if (Token::Match(backTok, "]|)"))
+                            backTok = backTok->link();
+                        backTok = backTok->previous();
+                    }
+                    if (Token::Match(backTok, "%name%")) {
+                        backTok->isAttributeMaybeUnused(true);
+                    }
                 } else {
-                    if (Token::simpleMatch(head->next(), "[")) {
+                    while (Token::Match(head->next(), "%name%|::|*|&|&&"))
+                        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);
+                    } else if (Token::simpleMatch(head->next(), "[")) {
                         head = head->next();
                         const Token *end = head->link();
-                        for (head = head->next(); end && head != end; head = head->next()) {
+                        for (head = head->next(); head != end; head = head->next()) {
                             if (Token::Match(head, "%name%")) {
                                 head->isAttributeMaybeUnused(true);
                             }

test/testtokenize.cpp

@@ -278,7 +278,8 @@ 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);
@@ -4260,7 +4261,7 @@ class TestTokenizer : public TestFixture {
         ASSERT(var && var->isAttributeMaybeUnused());
     }
 
-    void cppMaybeUnusedAfter() {
+    void cppMaybeUnusedAfter1() {
         const char code[] = "int var [[maybe_unused]] {};";
         const char expected[] = "int var { } ;";
 
@@ -4273,6 +4274,19 @@ 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 ( ) ;";

test/testunusedvar.cpp

@@ -6534,6 +6534,12 @@ 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