Is it possible to subclass a C struct in C++ and use pointers to the struct in C code?

Question

Is there a side effect in doing this:

C code:

struct foo {
      int k;
};

int ret_foo(const struct foo* f){ 
    return f.k; 
}

C++ c

Answer 1

I certainly not recommend using such weird subclassing. It would be better to change your design to use composition instead of inheritance. Just make one member

foo* m_pfoo;

in the bar class and it will do the same job.

Other thing you can do is to make one more class FooWrapper, containing the structure in itself with the corresponding getter method. Then you can subclass the wrapper. This way the problem with the virtual destructor is gone.