Zig heading toward a self-hosting compiler

#include <assert.h>
#include <errno.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

intptr_t arg_to_size(const char *arg) {
  assert(sizeof(intptr_t) == sizeof(long));

  errno = 0;
  char *endp;
  long result = strtol(arg, &endp, 0);
  if (errno) {
    perror("strtol");
    exit(EXIT_FAILURE);
  }
  if (*endp != '\0') {
    switch (*endp) {
    default:
      exit(EXIT_FAILURE);
      break;
    case 'k':
      result *= 1024;
      break;
    case 'm':
      result *= 1024 * 1024;
      break;
    case 'g':
      result *= 1024 * 1024 * 1024;
      break;
    }
  }
  return result;
}

int main(int argc, char *argv[]) {
  if (argc < 2)
    exit(EXIT_FAILURE);
  intptr_t inc = arg_to_size(argv[1]);
  if (inc < 0)
    exit(EXIT_FAILURE);

  printf("allocating 0x%lx bytes\n", (long)inc);
  void *prev = sbrk(inc);
  if (prev == (void *)(-1)) {
    perror("sbrk");
    exit(EXIT_FAILURE);
  }

  return EXIT_SUCCESS;
}

$ ./sbrk-large 24g
allocating 0x600000000 bytes

$ ./sbrk-large 28g
allocating 0x700000000 bytes
sbrk: Cannot allocate memory

brk(NULL)                               = 0x1d71000
brk(0x801d71000)                        = 0x1d71000

./sbrk-large 64g
allocating 0x1000000000 bytes