Fix

Author: web-flow

lib/checkother.cpp

@@ -3337,8 +3337,10 @@ static bool checkVariableAssignment(const Token* tok, const Settings& settings)
     const Variable* var = tok->variable();
     if (!var || !isLargeObject(var, settings))
         return false;
-    if (isVariableChanged(var, settings))
+    if (findVariableChanged(tok->tokAt(2), tok->scope()->bodyEnd, /*indirect*/ 0, var->declarationId(), /*globalvar*/ false, settings))
         return false;
+    if (var->isLocal() || (var->isArgument() && !var->isReference()))
+        return true;
     const Scope* scope = tok->scope();
     while (scope && scope->type != ScopeType::eFunction)
         scope = scope->nestedIn;

test/testother.cpp

@@ -9910,6 +9910,19 @@ class TestOther : public TestFixture {
               "    return c.size();\n"
               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        check("struct S {\n"
+              "    std::string m;\n"
+              "    int f(std::string s);\n"
+              "};\n"
+              "int S::f(std::string s) {\n"
+              "    s += m;\n"
+              "    std::string c = s;\n"
+              "    m.clear();\n"
+              "    return c.size();\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:7:17]: (performance, inconclusive) Use const reference for 'c' to avoid unnecessary data copying. [redundantCopyLocalConst]\n",
+                      errout_str());
     }
 
     void checkNegativeShift() {