Fixed #1856 (false positive: "pData" nulled but not freed upon failure)

lib/checkmemoryleak.cpp

@@ -2186,11 +2186,32 @@ void CheckMemoryLeakInFunction::checkScope(const Token *Tok1, const std::string
 void CheckMemoryLeakInFunction::checkReallocUsage()
 {
     const Token *tok = _tokenizer->tokens();
-    for (; tok; tok = tok->next())
+    while ((tok = Token::findmatch(tok, ") const| {")))
     {
-        if (Token::Match(tok, "%var% = realloc|g_try_realloc ( %var% ,"))
+        // Record the varid's of the function parameters
+        std::set<unsigned int> parameterVarIds;
+        for (tok = tok->link(); tok && tok->str() != "{"; tok = tok->next())
         {
-            if (tok->varId() == tok->tokAt(4)->varId())
+            if (tok->varId() != 0)
+                parameterVarIds.insert(tok->varId());
+        }
+
+        // Search for the "var = realloc(var, 100);" pattern within this function
+        unsigned int indentlevel = 0;
+        for (tok = tok->next(); tok; tok = tok->next())
+        {
+            if (tok->str() == "{")
+                ++indentlevel;
+            else if (tok->str() == "}")
+            {
+                if (indentlevel == 0)
+                    break;
+                --indentlevel;
+            }
+
+            if (Token::Match(tok, "%var% = realloc|g_try_realloc ( %var% ,") &&
+                tok->varId() == tok->tokAt(4)->varId() &&
+                parameterVarIds.find(tok->varId()) == parameterVarIds.end())
             {
                 memleakUponReallocFailureError(tok, tok->str());
             }

test/testmemleak.cpp

@@ -329,6 +329,7 @@ private:
         TEST_CASE(realloc4);
         TEST_CASE(realloc5);
         TEST_CASE(realloc6);
+        TEST_CASE(realloc7);
 
         TEST_CASE(assign);
 
@@ -2012,6 +2013,21 @@ private:
         ASSERT_EQUALS(";;alloc;", getcode("char *buf; buf=realloc(0,100);", "buf"));
     }
 
+    void realloc7()
+    {
+        check("bool foo(size_t nLen, char* pData)\n"
+              "{\n"
+              "    pData = (char*) realloc(pData, sizeof(char) + (nLen + 1)*sizeof(char));\n"
+              "    if ( pData == NULL )\n"
+              "    {\n"
+              "        return false;\n"
+              "    }\n"
+              "    free(pData);\n"
+              "    return true;\n"
+              "}\n", false);
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void assign()
     {
         check("void foo()\n"