pointer-arithmetics-challenge-using-offsetof

pointer-arithmetics-challenge-using-offsetof.c

#include <stdio.h>
#include <stddef.h>

/**
 * An example structure that holds members of different
 * types and sizes that we will be using in our example.
 */
typedef struct {
  float f;
  int member;
  char c;
} t_struct;

/**
 * A function returning a pointer to a structure of type `t_struct`
 * given a pointer to one of its member.
 */
t_struct* get_struct_ptr(void* member_ptr) {
  return (t_struct*)((char*) member_ptr - offsetof(t_struct, member));
}

int main(void)
{
  t_struct test;
  t_struct* ptr;
 
  ptr = get_struct_ptr(&test.member);
  if (ptr == &test) {
    printf("It works !\n");
  }
  return (0);
}