variadic_macros.c

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

// Based on https://stackoverflow.com/questions/1872220/is-it-possible-to-iterate-over-arguments-in-variadic-macros
struct a
{
  int a;
  int b;
  int c;
};

#define STRINGIZE(arg)  STRINGIZE1(arg)
#define STRINGIZE1(arg) STRINGIZE2(arg)
#define STRINGIZE2(arg) #arg

#define CONCATENATE(arg1, arg2)   CONCATENATE1(arg1, arg2)
#define CONCATENATE1(arg1, arg2)  CONCATENATE2(arg1, arg2)
#define CONCATENATE2(arg1, arg2)  arg1##arg2

#define FOR_EACH_1(what, x)         \
    what(x)

#define FOR_EACH_2(what, x, ...)    \
    what(x);                        \
    FOR_EACH_1(what, __VA_ARGS__);

#define FOR_EACH_3(what, x, ...)    \
    what(x);                        \
    FOR_EACH_2(what, __VA_ARGS__);

#define FOR_EACH_4(what, x, ...)    \
    what(x);                        \
    FOR_EACH_3(what,  __VA_ARGS__);

#define FOR_EACH_5(what, x, ...)    \
    what(x);                        \
    FOR_EACH_4(what,  __VA_ARGS__);

#define FOR_EACH_6(what, x, ...)    \
  what(x);                          \
  FOR_EACH_5(what,  __VA_ARGS__);

#define FOR_EACH_7(what, x, ...)    \
    what(x);                        \
    FOR_EACH_6(what,  __VA_ARGS__);

#define FOR_EACH_8(what, x, ...)    \
    what(x);                        \
    FOR_EACH_7(what,  __VA_ARGS__);

#define FOR_EACH_NARG(...) FOR_EACH_NARG_(__VA_ARGS__, FOR_EACH_RSEQ_N())
#define FOR_EACH_NARG_(...) FOR_EACH_ARG_N(__VA_ARGS__)
#define FOR_EACH_ARG_N(_1, _2, _3, _4, _5, _6, _7, _8, N, ...) N
#define FOR_EACH_RSEQ_N() 8, 7, 6, 5, 4, 3, 2, 1, 0

#define FOR_EACH_(N, what, ...) CONCATENATE(FOR_EACH_, N)(what, __VA_ARGS__)
#define FOR_EACH(what, ...) FOR_EACH_(FOR_EACH_NARG(__VA_ARGS__), what, __VA_ARGS__)

#define PRN_STRUCT_OFFSETS_(structure, field) printf(STRINGIZE(structure) ":" STRINGIZE(field)" - offset = %d\n", offsetof(structure, field));
#define PRN_STRUCT_OFFSETS(field) PRN_STRUCT_OFFSETS_(struct a, field)

int main(int argc, char *argv[])
{
  FOR_EACH(PRN_STRUCT_OFFSETS, a);
  printf("\n");

  return 0;
}