This is a demonstration showing how to print stack size of a certain function

stack_size.c

// We demonstrate how to get the stack usage of a function
// using the __builtin_frame_address function of GCC and clang.
//
// This function returns:
//    The frame is the area on the stack that holds local variables and saved registers.
//    The frame address is normally the address of the first word pushed on to
//    the stack by the function.
// 
// by saving its value and comparing it to a callee, we get the stack usage of this
// function.
//
// $ make stack_size
// cc     stack_size.c   -o stack_size
// $ ./stack_size
// stack size of big_func: 0x7ffee6b716e0-0x7ffee6b712d0 = 1040
// stack size of small_func: 0x7ffee6b716e0-0x7ffee6b716b0 = 48
#include <stdio.h>

void* last_frame_addr;

void
__attribute__ ((noinline))
_print_stack_size(const char* func_name) {
  printf("stack size of %s: %p-%p = %ld\n",
      func_name,
      last_frame_addr,
      __builtin_frame_address(0),
      last_frame_addr-__builtin_frame_address(0));
}

#define print_stack_size() _print_stack_size(__func__)

volatile int sink;

void big_func()
{
  char buf[1000];
  int i;
  last_frame_addr = __builtin_frame_address(0);
  buf[0] = 1;
  for (i=1;i<sizeof(buf);i++) {
    buf[i] = i + buf[i-1];
  }
  print_stack_size();
  for (i=0;i<sizeof(buf);i++) {
    sink = buf[i];
  }
}

void small_func()
{
  char buf[10];
  int i;
  buf[0] = 1;
  last_frame_addr = __builtin_frame_address(0);
  for (i=1;i<sizeof(buf);i++) {
    buf[i] = i + buf[i-1];
  }
  print_stack_size();
  for (i=0;i<sizeof(buf);i++) {
    sink = buf[i];
  }
}

int main() {
  big_func();
  small_func();
}