nimecho0.c

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

void nimecho (int n, ...) {
  typedef char* cptr;
  va_list ap;
  int i;
  int len = 0;
  char *dst0;
  char *dst;
  
  va_start (ap, n);
  for (i = 0; i < n; i++) {
    va_arg (ap, cptr);        // discard 
    len += va_arg (ap, int);
  }
  va_end (ap);
  
  len += 1;
  dst = dst0 = (char*) alloca (len);
  
  va_start (ap, n);
  for (i = 0; i < n; i++) {
    char *src = va_arg (ap, cptr);
    int slen = va_arg (ap, int);
    memcpy (dst, src, slen);
    dst += slen;
  }
  va_end (ap);
  *dst = '\n';
  fwrite (dst0, len, 1, stdout); 
}

#define COUNT(s) s,((int)sizeof(s)-1) 

void usenimecho () {
  nimecho (4, COUNT("dog"), COUNT("monkey"), COUNT("bird"), COUNT("rabbits"));  
} 

void useprintf () {
  printf ("%s%s%s%s\n", "dog", "monkey", "bird", "rabbits");  
} 

int main (int argc, char **argv) {
  
  fprintf (stderr, "%d\n", argc);

  if (argc < 2) return 1;

  auto testnimecho = usenimecho;


  switch (argv [1][0]) {
    case 'p': testnimecho = useprintf; break;
    case 'n': break;
    case '1':
      fprintf (stderr, "//useprintf\n");
      useprintf ();
      fprintf (stderr, "//usenimecho\n");
      usenimecho ();
      return 0;
    case '0':
      fprintf (stderr, "//printf\n");
      printf ("%s\n", "foo\0cow");
      fprintf (stderr, "//nimecho\n");
      nimecho (1, COUNT ("foo\0cow"));
      return 0;
    default: return 2;
  }

  fprintf (stderr, "usenimecho = %p\n", usenimecho);
  fprintf (stderr, "useprintf = %p\n", useprintf);
  fprintf (stderr, "%c\n", argv [1][0]);
  fprintf (stderr, "testnimecho = %p\n", testnimecho);

  for (auto i = 0; i < 9200000; i++) {
    testnimecho ();
  }

  return 0;
}

nimecho0_output.txt

$ g++ -std=c++11 -Wall -Werror -o nimecho nimecho.c

$ ./nimecho 0
2
//printf
foo
//nimecho
foocow