Fix #12807 (dump file: provide alignas expressions) (#6485)

cherry pick b84bc8d from main branch

Author: danmar

lib/token.h

@@ -121,6 +121,15 @@ struct TokenImpl {
     };
     CppcheckAttributes* mCppcheckAttributes{};
 
+    // alignas expressions
+    std::unique_ptr<std::vector<std::string>> mAttributeAlignas;
+    void addAttributeAlignas(const std::string& a) {
+        if (!mAttributeAlignas)
+            mAttributeAlignas = std::unique_ptr<std::vector<std::string>>(new std::vector<std::string>());
+        if (std::find(mAttributeAlignas->cbegin(), mAttributeAlignas->cend(), a) == mAttributeAlignas->cend())
+            mAttributeAlignas->push_back(a);
+    }
+
     // For memoization, to speed up parsing of huge arrays #8897
     enum class Cpp11init { UNKNOWN, CPP11INIT, NOINIT } mCpp11init = Cpp11init::UNKNOWN;
 
@@ -533,6 +542,15 @@ class CPPCHECKLIB Token {
     void isAttributeMaybeUnused(const bool value) {
         setFlag(fIsAttributeMaybeUnused, value);
     }
+    std::vector<std::string> getAttributeAlignas() const {
+        return mImpl->mAttributeAlignas ? *mImpl->mAttributeAlignas : std::vector<std::string>();
+    }
+    bool hasAttributeAlignas() const {
+        return !!mImpl->mAttributeAlignas;
+    }
+    void addAttributeAlignas(const std::string& a) {
+        mImpl->addAttributeAlignas(a);
+    }
     void setCppcheckAttribute(TokenImpl::CppcheckAttributes::Type type, MathLib::bigint value) {
         mImpl->setCppcheckAttribute(type, value);
     }

lib/tokenize.cpp

@@ -6026,6 +6026,13 @@ void Tokenizer::dump(std::ostream &out) const
             outs += " isAttributeMaybeUnused=\"true\"";
         if (tok->isAttributeUnused())
             outs += " isAttributeUnused=\"true\"";
+        if (tok->hasAttributeAlignas()) {
+            const std::vector<std::string>& a = tok->getAttributeAlignas();
+            outs += " alignas=\"" + ErrorLogger::toxml(a[0]) + "\"";
+            if (a.size() > 1)
+                // we could write all alignas expressions but currently we only need 2
+                outs += " alignas2=\"" + ErrorLogger::toxml(a[1]) + "\"";
+        }
         if (tok->link()) {
             outs += " link=\"";
             outs += id_string(tok->link());
@@ -9277,6 +9284,21 @@ 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
             }
         }

test/testtokenize.cpp

@@ -438,6 +438,7 @@ class TestTokenizer : public TestFixture {
 
         TEST_CASE(removeAlignas1);
         TEST_CASE(removeAlignas2); // Do not remove alignof in the same way
+        TEST_CASE(dumpAlignas);
 
         TEST_CASE(simplifyCoroutines);
 
@@ -7764,6 +7765,17 @@ class TestTokenizer : public TestFixture {
         ASSERT_EQUALS(expected, tokenizeAndStringify(code));
     }
 
+    void dumpAlignas() {
+        Settings settings;
+        SimpleTokenizer tokenizer(settings, *this);
+        tokenizer.tokenize("int alignas(8) alignas(16) x;", false);
+        ASSERT(Token::simpleMatch(tokenizer.tokens(), "int x ;"));
+        std::ostringstream ostr;
+        tokenizer.dump(ostr);
+        const std::string dump = ostr.str();
+        ASSERT(dump.find(" alignas=\"8\" alignas2=\"16\"") != std::string::npos);
+    }
+
     void simplifyCoroutines() {
         const Settings settings = settingsBuilder().cpp(Standards::CPP20).build();