assignFunctionArg: don't warn when there is self assignment. There is a separate warning for self assignments.

lib/checkautovariables.cpp

@@ -130,6 +130,7 @@ void CheckAutoVariables::assignFunctionArg()
         for (const Token *tok = scope->classStart; tok && tok != scope->classEnd; tok = tok->next()) {
             if (Token::Match(tok, "[;{}] %var% =|++|--") &&
                 isNonReferenceArg(tok->next()) &&
+                !Token::Match(tok->tokAt(2), "= %varid% ;", tok->next()->varId()) &&
                 !variableIsUsedInScope(Token::findsimplematch(tok->tokAt(2), ";"), tok->next()->varId(), scope) &&
                 !Token::findsimplematch(tok, "goto", scope->classEnd)) {
                 if (tok->next()->variable()->isPointer() && printWarning)

test/testautovariables.cpp

@@ -263,6 +263,11 @@ private:
               "}");
         ASSERT_EQUALS("[test.cpp:2]: (style) Assignment of function parameter has no effect outside the function.\n", errout.str());
 
+        check("void foo(char* p) {\n" // don't warn for self assignment, there is another warning for this
+              "  p = p;\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
+
         check("void foo(char* p) {\n"
               "    if (!p) p = buf;\n"
               "    *p = 0;\n"