com.asm

        auto bar2 = &bar;
00007FF6163D6647  lea         rax,[bar]  
00007FF6163D664B  mov         qword ptr [rbp+28h],rax  
        auto n = bar.func1();
00007FF6163D664F  lea         rcx,[bar]  
00007FF6163D6653  call        Bar::func1 (07FF6163D11F4h)  
00007FF6163D6658  mov         dword ptr [rbp+44h],eax  
        auto foo = bar.func2();
00007FF6163D665B  lea         rdx,[rbp+68h]  
00007FF6163D665F  lea         rcx,[bar]  
00007FF6163D6663  call        Bar::func2 (07FF6163D137Fh)  

        auto bar2 = reinterpret_cast<WrongBarCOM*>(&bar);
00007FF6163D66CD  lea         rax,[bar]  
00007FF6163D66D1  mov         qword ptr [rbp+88h],rax  
        auto n = bar2->vtbl->func1(&bar);
00007FF6163D66D8  mov         rax,qword ptr [rbp+88h]  
00007FF6163D66DF  mov         rax,qword ptr [rax]  
00007FF6163D66E2  lea         rcx,[bar]  
00007FF6163D66E6  call        qword ptr [rax]  
00007FF6163D66E8  mov         dword ptr [rbp+0A4h],eax  
        auto foo = bar2->vtbl->func2(&bar);
00007FF6163D66EE  mov         rax,qword ptr [rbp+88h]  
00007FF6163D66F5  mov         rax,qword ptr [rax]  
00007FF6163D66F8  lea         rcx,[bar]  
00007FF6163D66FC  call        qword ptr [rax+8]  
00007FF6163D66FF  mov         qword ptr [rbp+204h],rax  
00007FF6163D6706  mov         rax,qword ptr [rbp+204h]  
00007FF6163D670D  mov         qword ptr [rbp+0C8h],rax  

        auto bar2 = reinterpret_cast<CorrectBarCOM*>(&bar);
00007FF6163D6782  lea         rax,[bar]  
00007FF6163D6786  mov         qword ptr [rbp+0E8h],rax  
        auto n = bar2->vtbl->func1(&bar);
00007FF6163D678D  mov         rax,qword ptr [rbp+0E8h]  
00007FF6163D6794  mov         rax,qword ptr [rax]  
00007FF6163D6797  lea         rcx,[bar]  
00007FF6163D679B  call        qword ptr [rax]  
00007FF6163D679D  mov         dword ptr [rbp+104h],eax  
        Foo foo;
        bar2->vtbl->func2(&bar, &foo);
00007FF6163D67A3  mov         rax,qword ptr [rbp+0E8h]  
00007FF6163D67AA  mov         rax,qword ptr [rax]  
00007FF6163D67AD  lea         rdx,[rbp+128h]  
00007FF6163D67B4  lea         rcx,[bar]  
00007FF6163D67B8  call        qword ptr [rax+8]  

com.cpp

#include <iostream>
using namespace std;
struct Foo {
    int a;
    int b;
};
struct Bar {
    virtual int __stdcall func1() {
        return 273;
    }
    virtual Foo __stdcall func2() {
        return { 100, 200 };
    }
};
struct WrongBarVtbl {
    int(*__stdcall func1)(Bar *);
    Foo(*__stdcall func2)(Bar *);
};
struct WrongBarCOM {
    WrongBarVtbl * vtbl;
};
struct CorrectBarVtbl {
    int(*__stdcall func1)(Bar *);
    Foo*(*__stdcall func2)(Bar *, Foo *);
};
struct CorrectBarCOM {
    CorrectBarVtbl * vtbl;
};
int main() {
    Bar bar{};
    {
        auto bar2 = &bar;
        auto n = bar.func1();
        auto foo = bar.func2();
        cout << "C++: " << n << ", " << foo.a << ", " << foo.b << endl;
    }
    {
        auto bar2 = reinterpret_cast<WrongBarCOM*>(&bar);
        auto n = bar2->vtbl->func1(&bar);
        auto foo = bar2->vtbl->func2(&bar);
        cout << "Wrong: " << n << ", " << foo.a << ", " << foo.b << endl;
    }
    {
        auto bar2 = reinterpret_cast<CorrectBarCOM*>(&bar);
        auto n = bar2->vtbl->func1(&bar);
        Foo foo;
        bar2->vtbl->func2(&bar, &foo);
        cout << "Correct: " << n << ", " << foo.a << ", " << foo.b << endl;
    }
}