Compares the effect of delete-ing objects via base class pointer when the base class and/or child class lacks a virtual destructor

virtual_destructors.cpp

// Compares the effect of delete-ing objects via base class pointer
// when the base class and/or child class lacks a virtual destructor

#include <iostream>
#include <memory>

struct BaseMember
{
    BaseMember() { std::cout << "BaseMember()\n"; }
    ~BaseMember() { std::cout << "~BaseMember()\n"; }
};
struct ChildMember
{
    ChildMember() { std::cout << "ChildMember()\n"; }
    ~ChildMember() { std::cout << "~ChildMember()\n"; }
};

struct NonVirtual  // <-------- NON-VIRTUAL DESTRUCTOR
{
    NonVirtual() { std::cout << "NonVirtual()\n"; }
    ~NonVirtual() { std::cout << "~NonVirtual()\n"; }
    BaseMember bm;
};
struct NonVirtualWithVirtualDestructor : NonVirtual
{
    NonVirtualWithVirtualDestructor() { std::cout << "NonVirtualWithVirtualDestructor()\n"; }
    virtual ~NonVirtualWithVirtualDestructor() { std::cout << "~NonVirtualWithVirtualDestructor()\n"; }
    ChildMember cm;
};
struct NonVirtualWithNonVirtualDestructor : NonVirtual
{
    NonVirtualWithNonVirtualDestructor() { std::cout << "NonVirtualWithNonVirtualDestructor()\n"; }
    ~NonVirtualWithNonVirtualDestructor() { std::cout << "~NonVirtualWithNonVirtualDestructor()\n"; }
    ChildMember cm;
};

struct Virtual  // <-------- VIRTUAL DESTRUCTOR
{
    Virtual() { std::cout << "Virtual()\n"; }
    virtual ~Virtual() { std::cout << "~Virtual()\n"; }
    BaseMember bm;
};
struct VirtualWithVirtualDestructor : Virtual
{
    VirtualWithVirtualDestructor() { std::cout << "VirtualWithVirtualDestructor()\n"; }
    virtual ~VirtualWithVirtualDestructor() { std::cout << "~VirtualWithVirtualDestructor()\n"; }
    ChildMember cm;
};
struct VirtualWithNonVirtualDestructor : Virtual
{
    VirtualWithNonVirtualDestructor() { std::cout << "VirtualWithNonVirtualDestructor()\n"; }
    ~VirtualWithNonVirtualDestructor() { std::cout << "~VirtualWithNonVirtualDestructor()\n"; }
    ChildMember cm;
};

struct PureVirtual  // <-------- PURE VIRTUAL DESTRUCTOR
{
    PureVirtual() { std::cout << "PureVirtual()\n"; }
    virtual ~PureVirtual() = 0;
    BaseMember bm;
};
PureVirtual::~PureVirtual() { std::cout << "~PureVirtual()\n"; }

struct PureVirtualWithVirtualDestructor : PureVirtual
{
    PureVirtualWithVirtualDestructor() { std::cout << "PureVirtualWithVirtualDestructor()\n"; }
    virtual ~PureVirtualWithVirtualDestructor() { std::cout << "~PureVirtualWithVirtualDestructor()\n"; }
    ChildMember cm;
};
struct PureVirtualWithNonVirtualDestructor : PureVirtual
{
    PureVirtualWithNonVirtualDestructor() { std::cout << "PureVirtualWithNonVirtualDestructor()\n"; }
    ~PureVirtualWithNonVirtualDestructor() { std::cout << "~PureVirtualWithNonVirtualDestructor()\n"; }
    ChildMember cm;
};

struct DefaultVirtual  // <-------- DEFAULT VIRTUAL DESTRUCTOR
{
    DefaultVirtual() = default;
    virtual ~DefaultVirtual() = default;
    BaseMember bm;
};
struct DefaultVirtualWithVirtualDestructor : DefaultVirtual
{
    DefaultVirtualWithVirtualDestructor() { std::cout << "DefaultVirtualWithVirtualDestructor()\n"; }
    virtual ~DefaultVirtualWithVirtualDestructor() { std::cout << "~DefaultVirtualWithVirtualDestructor()\n"; }
    ChildMember cm;
};
struct DefaultVirtualWithNonVirtualDestructor : DefaultVirtual
{
    DefaultVirtualWithNonVirtualDestructor() { std::cout << "DefaultVirtualWithNonVirtualDestructor()\n"; }
    ~DefaultVirtualWithNonVirtualDestructor() { std::cout << "~DefaultVirtualWithNonVirtualDestructor()\n"; }
    ChildMember cm;
};

struct EmptyVirtual  // <-------- EMPTY VIRTUAL DESTRUCTOR
{
    EmptyVirtual() {}
    virtual ~EmptyVirtual() {}
    BaseMember bm;
};
struct EmptyVirtualWithVirtualDestructor : EmptyVirtual
{
    EmptyVirtualWithVirtualDestructor() { std::cout << "EmptyVirtualWithVirtualDestructor()\n"; }
    virtual ~EmptyVirtualWithVirtualDestructor() { std::cout << "~EmptyVirtualWithVirtualDestructor()\n"; }
    ChildMember cm;
};
struct EmptyVirtualWithNonVirtualDestructor : EmptyVirtual
{
    EmptyVirtualWithNonVirtualDestructor() { std::cout << "EmptyVirtualWithNonVirtualDestructor()\n"; }
    ~EmptyVirtualWithNonVirtualDestructor() { std::cout << "~EmptyVirtualWithNonVirtualDestructor()\n"; }
    ChildMember cm;
};

int main()
{
    std::cout << "-------- GOOD -----------------\n";
    {
        std::unique_ptr<Virtual> bcp(new VirtualWithVirtualDestructor());
    }
    std::cout << "-------- GOOD -----------------\n";
    {
        std::unique_ptr<Virtual> bcp(new VirtualWithNonVirtualDestructor());
    }
    std::cout << "-------- GOOD -----------------\n";
    {
        std::unique_ptr<PureVirtual> bcp(new PureVirtualWithVirtualDestructor());
    }
    std::cout << "-------- GOOD -----------------\n";
    {
        std::unique_ptr<PureVirtual> bcp(new PureVirtualWithNonVirtualDestructor());
    }
    std::cout << "-------- GOOD -----------------\n";
    {
        std::unique_ptr<DefaultVirtual> bcp(new DefaultVirtualWithVirtualDestructor());
    }
    std::cout << "-------- GOOD -----------------\n";
    {
        std::unique_ptr<DefaultVirtual> bcp(new DefaultVirtualWithNonVirtualDestructor());
    }
    std::cout << "-------- GOOD -----------------\n";
    {
        std::unique_ptr<EmptyVirtual> bcp(new EmptyVirtualWithVirtualDestructor());
    }
    std::cout << "-------- GOOD -----------------\n";
    {
        std::unique_ptr<EmptyVirtual> bcp(new EmptyVirtualWithNonVirtualDestructor());
    }
    std::cout << "-------- BAD -----------------\n";
    {
        std::unique_ptr<NonVirtual> bcp(new NonVirtualWithNonVirtualDestructor());
    }
    std::cout << "-------- CRASH -----------------\n";
    {
        std::unique_ptr<NonVirtual> bcp(new NonVirtualWithVirtualDestructor());
    }
}