Fixed #1792 (false positive: Variable 'test' is assigned a value that is never used)

lib/checkother.cpp

@@ -1378,6 +1378,9 @@ void CheckOther::functionVariableUsage()
             const Variables::VariableUsage &usage = it->second;
             const std::string &varname = usage._name->str();
 
+            if (usage._name->isUnused())
+                continue;
+
             if (usage.unused() && !usage._modified)
                 unusedVariableError(usage._name, varname);
 

lib/token.cpp

@@ -35,6 +35,7 @@ Token::Token(Token **t) :
     _isUnsigned(false),
     _isSigned(false),
     _isLong(false),
+    _isUnused(false),
     _varId(0),
     _next(0),
     _previous(0),

lib/token.h

@@ -172,6 +172,14 @@ public:
     {
         _isLong = size;
     }
+    bool isUnused() const
+    {
+        return _isUnused;
+    }
+    void isUnused(bool used)
+    {
+        _isUnused = used;
+    }
     bool isStandardType() const;
     bool isIntegerType() const;
 
@@ -368,6 +376,7 @@ private:
     bool _isUnsigned;
     bool _isSigned;
     bool _isLong;
+    bool _isUnused;
     unsigned int _varId;
     Token *_next;
     Token *_previous;

lib/tokenize.cpp

@@ -172,6 +172,7 @@ void Tokenizer::addtoken(const Token * tok, const unsigned int lineno, const uns
     _tokensBack->isUnsigned(tok->isUnsigned());
     _tokensBack->isSigned(tok->isSigned());
     _tokensBack->isLong(tok->isLong());
+    _tokensBack->isUnused(tok->isUnused());
 }
 //---------------------------------------------------------------------------
 
@@ -7678,6 +7679,16 @@ void Tokenizer::simplifyAttribute()
     {
         if (Token::simpleMatch(tok, "__attribute__ (") && tok->next()->link() && tok->next()->link()->next())
         {
+            if (Token::simpleMatch(tok->tokAt(2), "( unused )"))
+            {
+                // check if after variable name
+                if (Token::Match(tok->next()->link()->next(), ";|="))
+                {
+                    if (Token::Match(tok->previous(), "%type%"))
+                        tok->previous()->isUnused(true);
+                }
+            }
+
             Token::eraseTokens(tok, tok->next()->link()->next());
             tok->deleteThis();
         }

test/testunusedvar.cpp

@@ -105,6 +105,7 @@ private:
         TEST_CASE(localvarShift);       // 1 >> var
         TEST_CASE(localvarCast);
         TEST_CASE(localvarClass);
+        TEST_CASE(localvarUnused);
     }
 
     void structmember1()
@@ -1893,6 +1894,21 @@ private:
                               "}\n");
         ASSERT_EQUALS(std::string(""), errout.str());
     }
+
+    void localvarUnused()
+    {
+        functionVariableUsage("int foo()\n"
+                              "{\n"
+                              "    bool test __attribute__((unused));\n"
+                              "}\n");
+        ASSERT_EQUALS(std::string(""), errout.str());
+
+        functionVariableUsage("int foo()\n"
+                              "{\n"
+                              "    bool test __attribute__((unused)) = true;\n"
+                              "}\n");
+        ASSERT_EQUALS(std::string(""), errout.str());
+    }
 };
 
 REGISTER_TEST(TestUnusedVar)