Fix #12813 (Tokenizer: handle alignas in C11 code) (#6487)

Author: danmar

lib/tokenize.cpp

@@ -9299,7 +9299,11 @@ void Tokenizer::simplifyCppcheckAttribute()
 
 void Tokenizer::simplifyCPPAttribute()
 {
-    if ((isCPP() && mSettings.standards.cpp < Standards::CPP11) || (isC() && mSettings.standards.c < Standards::C23))
+    // 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));
+
+    if (!hasAlignas && !hasCppAttribute)
         return;
 
     for (Token *tok = list.front(); tok;) {
@@ -9308,6 +9312,10 @@ void Tokenizer::simplifyCPPAttribute()
             continue;
         }
         if (isCPPAttribute(tok)) {
+            if (!hasCppAttribute) {
+                tok = skipCPPOrAlignAttribute(tok)->next();
+                continue;
+            }
             if (Token::findsimplematch(tok->tokAt(2), "noreturn", tok->link())) {
                 Token * head = skipCPPOrAlignAttribute(tok)->next();
                 while (isCPPAttribute(head) || isAlignAttribute(head))
@@ -9359,23 +9367,29 @@ void Tokenizer::simplifyCPPAttribute()
                 }
             }
         } else {
-            if (Token::simpleMatch(tok, "alignas (")) {
-                Token* atok = nullptr;
-                if (Token::Match(tok->previous(), "%name%"))
-                    atok = tok->previous();
-                else {
-                    atok = tok;
-                    while (isCPPAttribute(atok) || isAlignAttribute(atok))
-                        atok = skipCPPOrAlignAttribute(atok)->next();
-                }
-                if (atok) {
-                    std::string a;
-                    for (const Token* t = tok->tokAt(2); t && t->str() != ")"; t = t->next())
-                        a += " " + t->str();
-                    if (a.size() > 1)
-                        atok->addAttributeAlignas(a.substr(1));
-                }
-                // alignment requirements could be checked here
+            // alignas(expr)
+
+            if (!hasAlignas) {
+                tok = skipCPPOrAlignAttribute(tok)->next();
+                continue;
+            }
+
+            // alignment requirements could be checked here
+
+            Token* atok = nullptr;
+            if (Token::Match(tok->previous(), "%name%"))
+                atok = tok->previous();
+            else {
+                atok = tok;
+                while (isCPPAttribute(atok) || isAlignAttribute(atok))
+                    atok = skipCPPOrAlignAttribute(atok)->next();
+            }
+            if (atok) {
+                std::string a;
+                for (const Token* t = tok->tokAt(2); t && t->str() != ")"; t = t->next())
+                    a += " " + t->str();
+                if (a.size() > 1)
+                    atok->addAttributeAlignas(a.substr(1));
             }
         }
         Token::eraseTokens(tok, skipCPPOrAlignAttribute(tok)->next());

test/testtokenize.cpp

@@ -439,6 +439,7 @@ class TestTokenizer : public TestFixture {
 
         TEST_CASE(removeAlignas1);
         TEST_CASE(removeAlignas2); // Do not remove alignof in the same way
+        TEST_CASE(removeAlignas3); // remove alignas in C11 code
         TEST_CASE(dumpAlignas);
 
         TEST_CASE(simplifyCoroutines);
@@ -7851,6 +7852,16 @@ class TestTokenizer : public TestFixture {
         ASSERT_EQUALS(expected, tokenizeAndStringify(code));
     }
 
+    void removeAlignas3() {
+        const char code[] = "alignas(16) int x;";
+        const char expected[] = "int x ;";
+        // According to cppreference alignas() is a C23 macro; but it is often available when compiling C11.
+        // Misra C has C11 examples with alignas.
+        // Microsoft provides alignas in C11.
+        ASSERT_EQUALS(expected, tokenizeAndStringify(code, true, Platform::Type::Native, false, Standards::CPP11, Standards::C11));
+        ASSERT_EQUALS(expected, tokenizeAndStringify(code, true, Platform::Type::Native, true, Standards::CPP11, Standards::C11));
+    }
+
     void dumpAlignas() {
         Settings settings;
         SimpleTokenizer tokenizer(settings, *this);