converting an IPv4 address to string would become x7.6 faster if the format string of sprintf was parsed at compile-time

gistfile1.c

$ cat ipv4addr.c 
#include <stdio.h>

struct ct_printf_t {
  char *str;
  size_t off;
};

struct ct_printf_t ct_printf_init(char *str)
{
  struct ct_printf_t ret;
  ret.str = str;
  ret.off = 0;
  return ret;
}

struct ct_printf_t ct_printf_c(struct ct_printf_t ctx, const char c)
{
  ctx.str[ctx.off++] = c;
  return ctx;
}

struct ct_printf_t ct_printf_u(struct ct_printf_t ctx, unsigned v)
{
  char tmp[10];
  int i = sizeof(tmp);

  if (v == 0) {
    ctx.str[ctx.off++] = '0';
    return ctx;
  }

  do {
    tmp[--i] = '0' + v % 10;
  } while ((v /= 10) != 0);
  do {
    ctx.str[ctx.off++] = tmp[i++];
  } while (i != sizeof(tmp));

  return ctx;
}

int main(int argc, char **argv)
{
  char buf[sizeof("255.255.255.255")];
  int i;
  unsigned addr;

  if (sscanf(argv[1], "%u", &addr) != 1) {
    fprintf(stderr, "usage: %s <addr-as-number>\n", argv[0]);
    return 1;
  }

  for (i = 0; i != 10000000; ++i) {
#ifdef USE_SPRINTF
    sprintf(buf, "%d.%d.%d.%d", (addr >> 24) & 0xff, (addr >> 16) & 0xff, (addr >> 8) & 0xff, addr & 0xff);
#else
    ct_printf_u(ct_printf_c(ct_printf_u(ct_printf_c(ct_printf_u(ct_printf_c(ct_printf_u(
      ct_printf_init(buf),
      (addr >> 24) & 0xff),
      '.'),
      (addr >> 16) & 0xff),
      '.'),
      (addr >> 8) & 0xff),
      '.'),
      addr & 0xff).off;
#endif
  }

  printf("result: %s\n", buf);

  return 0;
}
$ gcc -DUSE_SPRINTF -O2 ipv4addr.c && time ./a.out 1234567890
result: 73.150.2.210

real	0m2.110s
user	0m2.112s
sys	0m0.000s
$ gcc -O2 ipv4addr.c && time ./a.out 1234567890
result: 73.150.2.210

real	0m0.275s
user	0m0.274s
sys	0m0.002s