easy struct inheritance & pseudo-polymorphism vs strict aliasing

Question

If anybody answers my question, please don\'t tell me to use C++.

So, I\'m making a small library in C that uses an object-oriented approach. I chose to use

Answer 1

I don't think your idea about casting via char* is valid. The rule is:

An object shall have its stored value accessed only by an lvalue expression that has one of the following types

A sub-expression of your expression is compatible but the overall expression isn't compatible.

I think the only realistic approach is composition:

struct base {
  int a;
  int b;
  char c;

  void (*virtual_method)(base*/*this*/,int, char);

};

struct derived {
    struct base;
    unsigned int d;
};

I realize that's an intellectually unappealing way to achieve inheritance.

PS: I haven't put your virtual member function pointer in my derived class. It needs to be accessible from base so needs to be declared there (assuming it's a polymorphic function that exists for both base and derived). I've also added a this parameter to flesh out the model a touch.