#define _GNU_SOURCE
   /* Due to conditional compilation, this is GNU source only if the C library
      is GNU.
   */
#include <stdlib.h>
#include <string.h>

#include "nstring.h"

#ifdef __GNUC__
  #define HAVE_VASPRINTF 1
#else
  #define HAVE_VASPRINTF 0
#endif

void
vasprintfN(const char ** const resultP,
           const char *  const format,
           va_list             varargs) {

    char * result;

#if HAVE_VASPRINTF
    vasprintf(&result, format, varargs);

    if (result == NULL)
        *resultP = strsol;
    else
        *resultP = result;
#else
    /* We have a big compromise here.  To do this right, without a
       huge amount of work, we need to go through the variable
       arguments twice: once to determine how much memory to allocate,
       and once to format the string.  On some machines, you can
       simply make two copies of the va_list variable in normal C
       fashion, but on others you need va_copy, which is a relatively
       recent invention.  In particular, the simple va_list copy
       failed on an AMD64 Gcc Linux system in March 2006.  

       So instead, we just allocate 4K and truncate or waste as
       necessary.
    */
    size_t const allocSize = 4096;
    result = malloc(allocSize);
    
    if (result == NULL)
        *resultP = strsol;
    else {
        size_t realLen;

        vsnprintfN(result, allocSize, format, varargs, &realLen);
        
        if (realLen >= allocSize)
            strcpy(result + allocSize - 15, "<<<TRUNCATED");

        *resultP = result;
    }
#endif
}
