optacro.c

/* 
 * Quicky and dirty optional arguments. Requires (ANSI) C99.
 *
 * Good:
 * 1. Allows to convert any existing function to a optarg function.
 * 2. Typed parameters.
 *
 * So so:
 * 3. Simple defaults are possible but might result in compiler
 *     warnings that can be suppressed but ...
 *
 * Bad:
 * 4. Requires (ANSI) C99.
 * 5. Doesn't support repeated parameters (like Amiga tags), 
 *    but it's easy to have helpers generate structures with
 *    repeated content
 *
 */

#include <stdio.h>

typedef struct {
  int deadline;
  int n_headers;
} ns_send_opts_t;

// if compiled with -Wno-initializer-overrides, we can cleanly implement default values here
// #define ns_send(addr, body,...) ns_send_o(addr, body, (ns_send_opts_t){ .deadline=1, __VA_ARGS__})

#define ns_send(addr, body,...) ns_send_o(addr, body, (ns_send_opts_t){__VA_ARGS__})
void ns_send_o(char* addr, char* body, ns_send_opts_t opts) {
  printf("sending %s to %s, deadline: %d, headers: %d\n", addr, body, opts.deadline, opts.n_headers);
}

int main() {
  ns_send("foo", "bar", .deadline=360);
  return 0;
}