FizBuz in C - a bitwise based approach

fizbuz.c

#include <stdio.h>
#include <stdlib.h>

// calls `snprintf` with the correct fizbuz result.
//
// Note: zero modulus is questionable... but we assume it's fine.
//
// A response to Kevlin Henney's talk from 2019: https://youtu.be/SFv8Wm2HdNM
int fizzbuzz(char *dest, unsigned long dest_len, unsigned long num) {
  // construct bit based result for the 4 possible states of fizbuz
  unsigned s = !(num % 3);
  s |= (!(num % 5)) << 1;
  // convert result to string
  switch ((s & 3)) {
  case 0:
    return snprintf(dest, dest_len, "%lu", num);
  case 1:
    return snprintf(dest, dest_len, "fizz");
  case 2:
    return snprintf(dest, dest_len, "buzz");
  case 3:
    return snprintf(dest, dest_len, "fizzbuzz");
  }
}

// test...
int main(int argc, char const *argv[]) {
  const size_t test_limit = 32;
  for (size_t i = 1; i < test_limit; ++i) {
    char dest[32];
    fizzbuzz(dest, 32, i);
    fprintf(stderr, "%zu => %s\n", i, dest);
  }
  return 0;
}

This C code FizzBuzz function is a response to Kevlin Henney's talk from 2019: https://youtu.be/SFv8Wm2HdNM.

This structural function tests mod(3) and mod(5) only once before mapping the result to a return statement.