virtual-inheritance

Consider classic virtual inheritance diamond hierarchy. I wonder to know what is the right implementation of copy and swap idiom in such hierarchy. The example is a little artificial - and it is not very smart - as it would play good with default copy semantic for A,B,D classes. But just to illustrate the problem - please forget about the example weaknesses and provide the solution. So I have class D derived from 2 base classes (B<1>,B<2>) - each of B classes inherits virtually from A class. Each class has non trivial copy semantics with using of copy and swap idiom. The most derived D class

Is there a way to downcast from a virtual base class to a derived class when there are no virtual functions involved? Here's some code to demonstrate what I'm talking about: struct Base1 { int data; }; struct Base2 { char odd_size[9]; }; struct ViBase { double value; }; struct MostDerived : Base1, Base2, virtual ViBase { bool ok; }; void foo(ViBase &v) { MostDerived &md = somehow_cast<MostDerived&>(v); //but HOW? md.ok = true; } int main() { MostDerived md; foo(md); } Please note that the code is for demonstration only. My real scenario is fairly complex and involves template parameters and

I have three classes structured like this: #include <iostream> using namespace std; class Keyword { public: virtual float GetValue() = 0; }; class CharacterKeyword : public Keyword { public: virtual float GetValue(){return _value;} private: float _value; }; class MeasurementKeyword : public Keyword { public: virtual float GetValue(){return _value;} private: float _value; }; class AddressType : public CharacterKeyword, public MeasurementKeyword { private: float address; float addresExt; }; int main() { AddressType *a = new AddressType(); a->GetValue(); return 0; } I am getting the following: In

Consider the below code: #include<iostream> using namespace std; class A { public: A() {cout << "1";} A(const A &obj) {cout << "2";} }; class B: virtual A { public: B() {cout << "3";} B(const B & obj) {cout<< "4";} }; class C: virtual A { public: C() {cout << "5";} C(const C & obj) {cout << "6";} }; class D:B,C { public: D() {cout << "7";} D(const D & obj) {cout << "8";} }; int main() { D d1; cout << "\n"; D d(d1); } The output of the program is below: 1357 1358 So, for line D d(d1) the copy constructor of D class is bein called. During inheritance we need to explicitly call copy constructor

Consider the following code: #include <iostream> #include <typeinfo> #include <type_traits> using namespace std; struct A { int data; }; struct B1 : A {}; struct B2 : virtual A {}; struct Base1 : virtual A {}; struct Base2 : virtual A {}; struct Derived : Base1, Base2 {}; int main() { cout << sizeof(B1) << endl; cout << sizeof(B2) << endl; cout << sizeof(Derived) << endl; cout << std::is_polymorphic<B1>::value << endl; cout << std::is_polymorphic<B2>::value << endl; cout << std::is_polymorphic<Derived>::value << endl; return 0; } On my system it prints 4 8 12 0 0 0 Which means that none of