Fixed #2860, False positive: Returning value of strncat() reported as memory leak

http://sourceforge.net/apps/trac/cppcheck/ticket/2860

lib/tokenize.cpp

@@ -286,6 +286,7 @@ Token *Tokenizer::copyTokens(Token *dest, const Token *first, const Token *last)
         tok2->isSigned(tok->isSigned());
         tok2->isLong(tok->isLong());
         tok2->isUnused(tok->isUnused());
+        tok2->varId(tok->varId());
 
         // Check for links and fix them up
         if (tok2->str() == "(" || tok2->str() == "[" || tok2->str() == "{")
@@ -4655,6 +4656,8 @@ bool Tokenizer::simplifyTokenList()
         }
     }
 
+    simplifyReturn();
+
     removeRedundantAssignment();
 
     simplifyComma();
@@ -8401,7 +8404,6 @@ void Tokenizer::simplifyEnum()
     }
 }
 
-
 void Tokenizer::simplifyStd()
 {
     std::set<std::string> f;
@@ -9889,3 +9891,21 @@ void Tokenizer::removeUnnecessaryQualification()
     }
 }
 
+void Tokenizer::simplifyReturn()
+{
+    for (Token *tok = _tokens; tok; tok = tok->next())
+    {
+        if (Token::Match(tok, "return strncat ( %any% , %any% , %any% ) ;"))
+        {
+            // Change to: strncat ( %any% , %any% , %any% ) ;
+            tok->deleteNext();
+            tok->str("strncat");
+
+            // Change to: strncat ( %any% , %any% , %any% ) ; return %any% ;
+            tok->tokAt(8)->insertToken("return");
+            copyTokens(tok->tokAt(9), tok->tokAt(2), tok->tokAt(2));
+            tok->tokAt(10)->insertToken(";");
+        }
+    }
+}
+

lib/tokenize.h

@@ -666,6 +666,12 @@ public:
         return _varId;
     }
 
+    /**
+     * Simplify e.g. 'return(strncat(temp,"a",1));' into
+     * strncat(temp,"a",1); return temp;
+     */
+    void simplifyReturn();
+
 private:
     /** Disable copy constructor, no implementation */
     Tokenizer(const Tokenizer &);

test/testsimplifytokens.cpp

@@ -358,6 +358,7 @@ private:
         TEST_CASE(simplifyIfNotNull);
         TEST_CASE(simplifyVarDecl1); // ticket # 2682 segmentation fault
         TEST_CASE(simplifyVarDecl2); // ticket # 2834 segmentation fault
+        TEST_CASE(return_strncat); // ticket # 2860 Returning value of strncat() reported as memory leak
     }
 
     std::string tok(const char code[], bool simplify = true)
@@ -7080,6 +7081,23 @@ private:
         tok(code, false);
         ASSERT_EQUALS("", errout.str());
     }
+
+    void return_strncat()
+    {
+        const char code[] = "char *f()\n"
+                            "{\n"
+                            "    char *temp=malloc(2);\n"
+                            "    strcpy(temp,\"\");\n"
+                            "    return (strncat(temp,\"a\",1));\n"
+                            "}";
+        ASSERT_EQUALS("char * f ( ) { "
+                      "char * temp ; "
+                      "temp = malloc ( 2 ) ; "
+                      "strcpy ( temp , \"\" ) ; "
+                      "strncat ( temp , \"a\" , 1 ) ; "
+                      "return temp ; "
+                      "}", tok(code, true));
+    }
 };
 
 REGISTER_TEST(TestSimplifyTokens)