Refactorized CheckAutoVariables::assignFunctionArg():

- Splitted message into style message (assigning non-pointers) and warning message (assigning pointers)
- Support operator++/-- (#4793)

lib/checkautovariables.cpp

@@ -119,17 +119,23 @@ static bool variableIsUsedInScope(const Token* start, unsigned int varId, const
 
 void CheckAutoVariables::assignFunctionArg()
 {
-    if (!_settings->isEnabled("warning"))
+    bool style = _settings->isEnabled("style");
+    bool warning = _settings->isEnabled("warning");
+    if (!style && !warning)
         return;
+
     const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
     const std::size_t functions = symbolDatabase->functionScopes.size();
     for (std::size_t i = 0; i < functions; ++i) {
         const Scope * scope = symbolDatabase->functionScopes[i];
         for (const Token *tok = scope->classStart; tok && tok != scope->classEnd; tok = tok->next()) {
-            if (Token::Match(tok, "[;{}] %var% =") &&
+            if (Token::Match(tok, "[;{}] %var% =|++|--") &&
                 isNonReferenceArg(tok->next()) &&
                 !variableIsUsedInScope(Token::findsimplematch(tok->tokAt(2), ";"), tok->next()->varId(), scope)) {
-                errorUselessAssignmentPtrArg(tok->next());
+                if (tok->next()->variable()->isPointer() && warning)
+                    errorUselessAssignmentPtrArg(tok->next());
+                else if (style)
+                    errorUselessAssignmentArg(tok->next());
             }
         }
     }
@@ -274,12 +280,20 @@ void CheckAutoVariables::errorReturnAddressOfFunctionParameter(const Token *tok,
                 "value is invalid.");
 }
 
+void CheckAutoVariables::errorUselessAssignmentArg(const Token *tok)
+{
+    reportError(tok,
+                Severity::style,
+                "uselessAssignmentArg",
+                "Assignment of function parameter has no effect outside the function.");
+}
+
 void CheckAutoVariables::errorUselessAssignmentPtrArg(const Token *tok)
 {
     reportError(tok,
                 Severity::warning,
                 "uselessAssignmentPtrArg",
-                "Assignment of function parameter has no effect outside the function.");
+                "Assignment of function parameter has no effect outside the function. Did you forget dereferencing it?");
 }
 
 //---------------------------------------------------------------------------

lib/checkautovariables.h

@@ -87,6 +87,7 @@ private:
     void errorReturnTempReference(const Token *tok);
     void errorInvalidDeallocation(const Token *tok);
     void errorReturnAddressOfFunctionParameter(const Token *tok, const std::string &varname);
+    void errorUselessAssignmentArg(const Token *tok);
     void errorUselessAssignmentPtrArg(const Token *tok);
 
     void getErrorMessages(ErrorLogger *errorLogger, const Settings *settings) const {
@@ -98,6 +99,7 @@ private:
         c.errorReturnTempReference(0);
         c.errorInvalidDeallocation(0);
         c.errorReturnAddressOfFunctionParameter(0, "parameter");
+        c.errorUselessAssignmentArg(0);
         c.errorUselessAssignmentPtrArg(0);
     }
 
@@ -112,7 +114,8 @@ private:
                "* assigning address of an variable to an effective parameter of a function\n"
                "* returning reference to local/temporary variable\n"
                "* returning address of function parameter\n"
-               "* useless assignment of pointer parameter\n";
+               "* suspicious assignment of pointer argument\n"
+               "* useless assignment of function argument\n";
     }
 };
 /// @}

test/testautovariables.cpp

@@ -41,6 +41,7 @@ private:
         Settings settings;
         settings.inconclusive = inconclusive;
         settings.addEnabled("warning");
+        settings.addEnabled("style");
 
         // Tokenize..
         Tokenizer tokenizer(&settings, this);
@@ -132,7 +133,7 @@ private:
               "    int num = 2;\n"
               "    res = #\n"
               "}");
-        ASSERT_EQUALS("[test.cpp:4]: (warning) Assignment of function parameter has no effect outside the function.\n", errout.str());
+        ASSERT_EQUALS("[test.cpp:4]: (warning) Assignment of function parameter has no effect outside the function. Did you forget dereferencing it?\n", errout.str());
 
         check("void func1(int **res)\n"
               "{\n"
@@ -161,7 +162,7 @@ private:
               "    int num = 2;\n"
               "    res = #\n"
               "}");
-        ASSERT_EQUALS("[test.cpp:7]: (warning) Assignment of function parameter has no effect outside the function.\n", errout.str());
+        ASSERT_EQUALS("[test.cpp:7]: (warning) Assignment of function parameter has no effect outside the function. Did you forget dereferencing it?\n", errout.str());
 
         check("class Fred {\n"
               "    void func1(int **res);\n"
@@ -264,12 +265,12 @@ private:
         check("void foo(char* p) {\n"
               "    p = 0;\n"
               "}");
-        ASSERT_EQUALS("[test.cpp:2]: (warning) Assignment of function parameter has no effect outside the function.\n", errout.str());
+        ASSERT_EQUALS("[test.cpp:2]: (warning) Assignment of function parameter has no effect outside the function. Did you forget dereferencing it?\n", errout.str());
 
         check("void foo(int b) {\n"
               "    b = foo(b);\n"
               "}");
-        ASSERT_EQUALS("[test.cpp:2]: (warning) Assignment of function parameter has no effect outside the function.\n", errout.str());
+        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"
               "    if (!p) p = buf;\n"
@@ -297,13 +298,13 @@ private:
         check("void foo(Foo* p) {\n"
               "    p = 0;\n"
               "}");
-        ASSERT_EQUALS("[test.cpp:2]: (warning) Assignment of function parameter has no effect outside the function.\n", errout.str());
+        ASSERT_EQUALS("[test.cpp:2]: (warning) Assignment of function parameter has no effect outside the function. Did you forget dereferencing it?\n", errout.str());
 
         check("class Foo {};\n"
               "void foo(Foo p) {\n"
               "    p = 0;\n"
               "}");
-        ASSERT_EQUALS("[test.cpp:3]: (warning) Assignment of function parameter has no effect outside the function.\n", errout.str());
+        ASSERT_EQUALS("[test.cpp:3]: (style) Assignment of function parameter has no effect outside the function.\n", errout.str());
 
         check("void foo(Foo p) {\n"
               "    p = 0;\n"
@@ -321,6 +322,11 @@ private:
               "    return d;"
               "}",false,false);
         ASSERT_EQUALS("", errout.str());
+
+        check("void foo(int* ptr) {\n" // #4793
+              "    ptr++;\n"
+              "}");
+        ASSERT_EQUALS("[test.cpp:2]: (warning) Assignment of function parameter has no effect outside the function. Did you forget dereferencing it?\n", errout.str());
     }
 
     void testautovar11() { // #4641 - fp, assign local struct member address to function parameter