compat_vasprintf.c

   1 /* $Id: compat_vasprintf.c,v 1.4 2020/06/15 01:37:15 schwarze Exp $ */
   2 /*
   3  * Copyright (c) 2015 Ingo Schwarze <schwarze@openbsd.org>
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  *
  17  * This fallback implementation is not efficient:
  18  * It does the formatting twice.
  19  * Short of fiddling with the unknown internals of the system's
  20  * printf(3) or completely reimplementing printf(3), i can't think
  21  * of another portable solution.
  22  */
  23 #include "config.h"
  24
  25 #include <stdarg.h>
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28
  29 int
  30 vasprintf(char **ret, const char *format, va_list ap)
  31 {
  32         char     buf[2];
  33         va_list  ap2;
  34         int      sz;
  35
  36         va_copy(ap2, ap);
  37         sz = vsnprintf(buf, sizeof(buf), format, ap2);
  38         va_end(ap2);
  39
  40         if (sz != -1 && (*ret = malloc(sz + 1)) != NULL) {
  41                 if (vsnprintf(*ret, sz + 1, format, ap) == sz)
  42                         return sz;
  43                 free(*ret);
  44         }
  45         *ret = NULL;
  46         return -1;
  47 }