Question

Trying to understand what the pointer to function actually represent? Is it the address in the code segment where the function resides?

For ex: this piece of code:

#include <stdio.h>

void foo(void)
{
}

int main(void)
{
    int a = 10;
    printf("a's address: %p\n", &a);
    printf("foo's address: %p\n", foo);
    return 0;
}

… prints this:

[sh/prog-exercises/adam]:./a.out 
a's address: 0xbfffb414 
foo's address: 0x8048430

I guess I am a little confused with how exactly stack/heap of a process relates with the ELF data-segment/code-segment. Any helpful pointers would be really welcome. Also, my first question, so please be gentle, am really trying to learn. Thanks!

Answer 1

That’s the address of the function entry point – start of its code. The a variable is located on stack, so no surprise its address differs significantly – stack and code are assigned different code regions taht can be quite far apart.