Just an example of how to get the size of a function in bytes using the GCC compiler

get-function-size.c

// See how it's works using: gcc -S get-function-size.c -o get-function-size.s
// To manually check function size: objdump -d get-function-size
#include <stdio.h>

#define DECLARE_FUNCSIZE(funcname)         \
  extern unsigned int funcname##_funcsize; \
  asm(#funcname "_funcsize: .long . - " #funcname "\n\t")

#define FUNCSIZE(funcname) \
  funcname##_funcsize

int add(int x, int y)
{
  return x + y;
}
DECLARE_FUNCSIZE(add); // Need to be declared immediately after the function declaration!

int main(void)
{
  printf("Size: %d\n", FUNCSIZE(add));
  return 0;
}