Fixed #11101 (False positive: derived union members are initialized in constructor)

Author: danmar

lib/checkclass.cpp

@@ -124,6 +124,28 @@ static bool isVclTypeInit(const Type *type)
     return false;
 }
 
+// Plain old C struct?
+static bool isPodStruct(const Scope *scope) {
+    if (scope->type != Scope::ScopeType::eStruct && scope->type != Scope::ScopeType::eUnion)
+        return false;
+    if (!scope->functionList.empty())
+        return false;
+    for (const Variable& var: scope->varlist) {
+        if (!var.valueType())
+            return false;
+        if (var.valueType()->isIntegral() || var.valueType()->pointer || var.valueType()->isFloat())
+            continue;
+        if (var.valueType()->typeScope && isPodStruct(var.valueType()->typeScope))
+            continue;
+        return false;
+    }
+    for (const Scope* childScope: scope->nestedList) {
+        if (!isPodStruct(childScope))
+            return false;
+    }
+    return true;
+}
+
 //---------------------------------------------------------------------------
 
 CheckClass::CheckClass(const Tokenizer *tokenizer, const Settings *settings, ErrorLogger *errorLogger)
@@ -298,17 +320,30 @@ void CheckClass::constructors()
                     const Scope *varType = var.typeScope();
                     if (!varType || varType->type != Scope::eUnion) {
                         const bool derived = scope != var.scope();
+                        // is the derived variable declared in a plain old C struct
+                        bool varScopeIsPodStruct = false;
+                        if (derived && scope->definedType && scope->definedType->derivedFrom.size() > 0) {
+                            for (const Scope* s = var.scope(); s; s = s ? s->nestedIn : nullptr) {
+                                for (const Type::BaseInfo& baseInfo: scope->definedType->derivedFrom) {
+                                    if (s->definedType == baseInfo.type) {
+                                        varScopeIsPodStruct = isPodStruct(s);
+                                        s = nullptr;
+                                        break;
+                                    }
+                                }
+                            }
+                        }
                         if (func.type == Function::eConstructor &&
                             func.nestedIn && (func.nestedIn->numConstructors - func.nestedIn->numCopyOrMoveConstructors) > 1 &&
                             func.argCount() == 0 && func.functionScope &&
                             func.arg && func.arg->link()->next() == func.functionScope->bodyStart &&
                             func.functionScope->bodyStart->link() == func.functionScope->bodyStart->next()) {
                             // don't warn about user defined default constructor when there are other constructors
-                            if (printInconclusive)
+                            if (printInconclusive && (!derived || !varScopeIsPodStruct))
                                 uninitVarError(func.token, func.access == AccessControl::Private, func.type, var.scope()->className, var.name(), derived, true);
                         } else if (missingCopy)
                             missingMemberCopyError(func.token, func.type, var.scope()->className, var.name());
-                        else
+                        else if (!derived || !varScopeIsPodStruct)
                             uninitVarError(func.token, func.access == AccessControl::Private, func.type, var.scope()->className, var.name(), derived, false);
                     }
                 }

test/testconstructors.cpp

@@ -126,6 +126,7 @@ class TestConstructors : public TestFixture {
         TEST_CASE(initvar_delegate);       // ticket #4302
         TEST_CASE(initvar_delegate2);
         TEST_CASE(initvar_derived_class);
+        TEST_CASE(initvar_derived_pod_struct); // #11101
 
         TEST_CASE(initvar_private_constructor);     // BUG 2354171 - private constructor
         TEST_CASE(initvar_copy_constructor); // ticket #1611
@@ -1416,6 +1417,24 @@ class TestConstructors : public TestFixture {
 
     }
 
+    void initvar_derived_pod_struct() {
+        check("struct S {\n"
+              "    union {\n"
+              "        unsigned short       all;\n"
+              "        struct {\n"
+              "            unsigned char    flag1;\n"
+              "            unsigned char    flag2;\n"
+              "        };\n"
+              "    };\n"
+              "};\n"
+              "\n"
+              "class C : public S {\n"
+              "public:\n"
+              "    C() { all = 0; tick = 0; }\n"
+              "};");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void initvar_private_constructor() {
         settings.standards.cpp = Standards::CPP11;
         check("class Fred\n"