Casting a function pointer to another type

Question

Let\'s say I have a function that accepts a void (*)(void*) function pointer for use as a callback:

void do_stuff(void (*callback_fp)(void*), vo         


        

Answer 1

As C code compiles to instruction which do not care at all about pointer types, it's quite fine to use the code you mention. You'd run into problems when you'd run do_stuff with your callback function and pointer to something else then my_struct structure as argument.

I hope I can make it clearer by showing what would not work:

int my_number = 14;
do_stuff((void (*)(void*)) &my_callback_function, &my_number);
// my_callback_function will try to access int as struct my_struct
// and go nuts

or...

void another_callback_function(struct my_struct* arg, int arg2) { something }
do_stuff((void (*)(void*)) &another_callback_function, NULL);
// another_callback_function will look for non-existing second argument
// on the stack and go nuts

Basically, you can cast pointers to whatever you like, as long as the data continue to make sense at run-time.