Runtime polymorphism in C

Question

Can someone please give me a simple explanation of how to achieve or emulate run-time polymorphism in C.

Also, is this a valid example of runtime-polymorphism:

void fred(){
  printf("Fred here!\n"); 
}

void john(){
  printf("John here\n");
}

void barbara ( void (*function_ptr)() ){
  (*function_ptr)();
}

int main(){
  barbara (fred);
  barbara (john);
  return 0;
}

The function barbara dynamically calls either john() or fred(). Is this what runtime polymorphism exactly is?

What is runtime? You alredy know compile time what it is calling :D — Digital_Reality, Jan 02 '14 at 04:55
Please [don't use signatures or taglines in your posts](http://stackoverflow.com/faq#signatures). — user229044, Jan 02 '14 at 05:01

score 1 · Answer 1 · answered Jan 02 '14 at 05:17

The function barbara dynamically calls either john() or fred().

No, it doesn't. barbara() calls whichever function you pass it as a parameter. barbara() does exactly the same thing no matter what you pass it -- namely, it executes the function that you pass as a parameter.

Is this what runtime polymorphism exactly is?

No. If barbara() looked at the parameter and changed its behavior based on some features (especially the type) of the parameter, then you'd be closer to polymorphism.

Runtime polymorphism in C

1 Answers1