Implement support for __attribute__((used)) (#3408)

lib/checkunusedvar.cpp

@@ -1093,7 +1093,7 @@ void CheckUnusedVar::checkFunctionVariableUsage()
             const Variable* var = symbolDatabase->getVariableFromVarId(it->first);
 
             // variable has been marked as unused so ignore it
-            if (usage._var->nameToken()->isAttributeUnused())
+            if (usage._var->nameToken()->isAttributeUnused() || usage._var->nameToken()->isAttributeUsed())
                 continue;
 
             // skip things that are only partially implemented to prevent false positives

lib/token.h

@@ -331,6 +331,12 @@ public:
     void isAttributeUnused(bool unused) {
         setFlag(fIsAttributeUnused, unused);
     }
+    bool isAttributeUsed() const {
+        return getFlag(fIsAttributeUsed);
+    }
+    void isAttributeUsed(bool unused) {
+        setFlag(fIsAttributeUsed, unused);
+    }
     bool isAttributePure() const {
         return getFlag(fIsAttributePure);
     }
@@ -743,7 +749,8 @@ private:
         fIsAttributePure        = (1 << 9),  // __attribute__((pure))
         fIsAttributeConst       = (1 << 10), // __attribute__((const))
         fIsAttributeNothrow     = (1 << 11), // __attribute__((nothrow))
-        fIsDeclspecNothrow      = (1 << 12)  // __declspec(nothrow)
+        fIsDeclspecNothrow      = (1 << 12), // __declspec(nothrow)
+        fIsAttributeUsed        = (1 << 13)  // __attribute__((used))
     };
 
     unsigned int _flags;

lib/tokenize.cpp

@@ -111,18 +111,7 @@ Token *Tokenizer::copyTokens(Token *dest, const Token *first, const Token *last,
         tok2->fileIndex(commonFileIndex);
         tok2->linenr(linenrs);
         tok2->type(tok->type());
-        tok2->isUnsigned(tok->isUnsigned());
+        tok2->flags(tok2->flags());
-        tok2->isSigned(tok->isSigned());
-        tok2->isPointerCompare(tok->isPointerCompare());
-        tok2->isLong(tok->isLong());
-        tok2->isExpandedMacro(tok->isExpandedMacro());
-        tok2->isAttributeConstructor(tok->isAttributeConstructor());
-        tok2->isAttributeDestructor(tok->isAttributeDestructor());
-        tok2->isAttributeUnused(tok->isAttributeUnused());
-        tok2->isAttributePure(tok->isAttributePure());
-        tok2->isAttributeConst(tok->isAttributeConst());
-        tok2->isAttributeNothrow(tok->isAttributeNothrow());
-        tok2->isDeclspecNothrow(tok->isDeclspecNothrow());
         tok2->varId(tok->varId());
 
         // Check for links and fix them up
@@ -9248,6 +9237,18 @@ void Tokenizer::simplifyAttribute()
                     tok->next()->link()->next()->isAttributeUnused(true);
             }
 
+            else if (Token::Match(tok->tokAt(2), "( used|__used__ )")) {
+                // check if after variable name
+                if (Token::Match(tok->next()->link()->next(), ";|=")) {
+                    if (Token::Match(tok->previous(), "%type%"))
+                        tok->previous()->isAttributeUsed(true);
+                }
+
+                // check if before variable name
+                else if (Token::Match(tok->next()->link()->next(), "%type%"))
+                    tok->next()->link()->next()->isAttributeUsed(true);
+            }
+
             else if (Token::Match(tok->tokAt(2), "( pure|__pure__ )")) {
                 // type func(...) __attribute__((pure));
                 if (tok->previous() && tok->previous()->link() && Token::Match(tok->previous()->link()->previous(), "%var% ("))

test/testunusedvar.cpp

@@ -3240,6 +3240,18 @@ private:
                               "    bool __attribute__((unused)) test = true;\n"
                               "}");
         ASSERT_EQUALS("", errout.str());
+
+        functionVariableUsage("int foo()\n"
+                              "{\n"
+                              "    bool test __attribute__((used));\n"
+                              "}");
+        ASSERT_EQUALS("", errout.str());
+
+        functionVariableUsage("int foo()\n"
+                              "{\n"
+                              "    bool __attribute__((used)) test;\n"
+                              "}");
+        ASSERT_EQUALS("", errout.str());
     }
 
     void localvarFunction() {