lib/vsprintf.c

   1 /* Formatted output to strings.
   2    Copyright (C) 2004, 2006-2024 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation, either version 3 of the
   7    License, or (at your option) any later version.
   8
   9    This file is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #ifdef HAVE_CONFIG_H
  18 # include <config.h>
  19 #endif
  20
  21 /* Specification.  */
  22 #include <stdio.h>
  23
  24 #include <errno.h>
  25 #include <limits.h>
  26 #include <stdarg.h>
  27 #include <stdint.h>
  28 #include <stdlib.h>
  29
  30 #include "vasnprintf.h"
  31
  32 #ifndef SIZE_MAX
  33 # define SIZE_MAX ((size_t) -1)
  34 #endif
  35
  36 /* Print formatted output to string STR.
  37    Return string length of formatted string.  On error, return a negative
  38    value.  */
  39 int
  40 vsprintf (char *str, const char *format, va_list args)
  41 {
  42   char *output;
  43   size_t len;
  44   size_t lenbuf;
  45
  46   /* vasnprintf fails with EOVERFLOW when the buffer size argument is larger
  47      than INT_MAX (if that fits into a 'size_t' at all).
  48      Also note that glibc's iconv fails with E2BIG when we pass a length that
  49      is so large that str + lenbuf wraps around, i.e.
  50      (uintptr_t) (str + lenbuf) < (uintptr_t) str.
  51      Therefore set lenbuf = min (SIZE_MAX, INT_MAX, - (uintptr_t) str - 1).  */
  52   lenbuf = (SIZE_MAX < INT_MAX ? SIZE_MAX : INT_MAX);
  53   if (lenbuf > ~ (uintptr_t) str)
  54     lenbuf = ~ (uintptr_t) str;
  55
  56   output = vasnprintf (str, &lenbuf, format, args);
  57   len = lenbuf;
  58
  59   if (!output)
  60     return -1;
  61
  62   if (output != str)
  63     {
  64       /* len is near SIZE_MAX.  */
  65       free (output);
  66       errno = EOVERFLOW;
  67       return -1;
  68     }
  69
  70   if (len > INT_MAX)
  71     {
  72       errno = EOVERFLOW;
  73       return -1;
  74     }
  75
  76   return len;
  77 }