use short for bit count, print error on larger values

Author: ludviggunne

lib/token.h

@@ -82,7 +82,7 @@ struct TokenImpl {
     nonneg int mIndex{};
 
     /** Bitfield bit count. */
-    MathLib::bigint mBits = -1;
+    short mBits = -1;
 
     // AST..
     Token* mAstOperand1{};
@@ -753,7 +753,7 @@ class CPPCHECKLIB Token {
     bool isBitfield() const {
         return mImpl->mBits >= 0;
     }
-    MathLib::bigint bits() const {
+    short bits() const {
         return mImpl->mBits;
     }
     const std::set<TemplateSimplifier::TokenAndName*>* templateSimplifierPointers() const {
@@ -767,8 +767,14 @@ class CPPCHECKLIB Token {
             mImpl->mTemplateSimplifierPointers = new std::set<TemplateSimplifier::TokenAndName*>;
         mImpl->mTemplateSimplifierPointers->insert(tokenAndName);
     }
-    void setBits(const MathLib::bigint b) {
-        mImpl->mBits = b;
+    bool setBits(const MathLib::bigint b) {
+        const MathLib::bigint max = std::numeric_limits<short>::max();
+        if (b > max) {
+            mImpl->mBits = max;
+            return false;
+        }
+        mImpl->mBits = b < 0 ? -1 : b;
+        return true;
     }
 
     bool isUtf8() const {

lib/tokenize.cpp

@@ -10007,6 +10007,14 @@ void Tokenizer::simplifyBitfields()
             }
         }
 
+        const auto tooLargeError = [this](const Token *tok) {
+            const MathLib::bigint max = std::numeric_limits<short>::max();
+            reportError(tok,
+                        Severity::warning,
+                        "tooLargeBitField",
+                        "Bit-field size exceeds max number of bits " + std::to_string(max));
+        };
+
         Token* typeTok = tok->next();
         while (Token::Match(typeTok, "const|volatile"))
             typeTok = typeTok->next();
@@ -10015,7 +10023,8 @@ void Tokenizer::simplifyBitfields()
             !Token::simpleMatch(tok->tokAt(2), "default :")) {
             Token *tok1 = typeTok->next();
             if (Token::Match(tok1, "%name% : %num% [;=]"))
-                tok1->setBits(MathLib::toBigNumber(tok1->tokAt(2)));
+                if (!tok1->setBits(MathLib::toBigNumber(tok1->tokAt(2))))
+                    tooLargeError(tok1->tokAt(2));
             if (tok1 && tok1->tokAt(2) &&
                 (Token::Match(tok1->tokAt(2), "%bool%|%num%") ||
                  !Token::Match(tok1->tokAt(2), "public|protected|private| %type% ::|<|,|{|;"))) {
@@ -10040,10 +10049,13 @@ void Tokenizer::simplifyBitfields()
             const std::string name = "anonymous@" + std::to_string(id);
             Token *newTok = typeTok->insertToken(name);
             newTok->isAnonymous(true);
+            bool failed;
             if (newTok->tokAt(2)->isBoolean())
-                newTok->setBits(newTok->strAt(2) == "true");
+                failed = !newTok->setBits(newTok->strAt(2) == "true");
             else
-                newTok->setBits(MathLib::toBigNumber(newTok->tokAt(2)));
+                failed = !newTok->setBits(MathLib::toBigNumber(newTok->tokAt(2)));
+            if (failed)
+                tooLargeError(newTok->tokAt(2));
             newTok->deleteNext(2);
         }