libs-base/config/config.vasprintf.c

/* Exit with status 0 if vasprintf returns the length of the string printed.
   Some systems return a pointer to the string instead. */ 
#include <stdio.h>
#include <stdarg.h>

static int func(const char *fmt, ...)
{
  va_list ap;
  char *buf;
  int result;

  va_start(ap, fmt);
  result = vasprintf(&buf, fmt, ap);
  va_end(ap);
  return result;
}

int main()
{
  if (func("1234", 0) == 4)
    exit (0);
  exit (-1);
}