lib/unistdio/u-vsprintf.h

   1 /* Formatted output to strings.
   2    Copyright (C) 1999, 2002, 2006-2020 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify it
   5    under the terms of the GNU Lesser General Public License as published
   6    by the Free Software Foundation; either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program 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 GNU
  12    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 #ifndef SIZE_MAX
  18 # define SIZE_MAX ((size_t) -1)
  19 #endif
  20
  21 int
  22 VSPRINTF (DCHAR_T *buf, const FCHAR_T *format, va_list args)
  23 {
  24   /* Pass an infinite length.  But note that *vasnprintf may fail if the buffer
  25      argument is larger than INT_MAX (if that fits into a 'size_t' at all).
  26      Also note that glibc's iconv fails with E2BIG when we pass a length that
  27      is so large that buf + length wraps around, i.e.
  28      (uintptr_t) (buf + length) < (uintptr_t) buf.  */
  29   size_t length;
  30   DCHAR_T *result;
  31
  32   /* Set length = min (SIZE_MAX, INT_MAX, - (uintptr_t) buf - 1).  */
  33   length = (SIZE_MAX < INT_MAX ? SIZE_MAX : INT_MAX);
  34   if (length > (~ (uintptr_t) buf) / sizeof (DCHAR_T))
  35     length = (~ (uintptr_t) buf) / sizeof (DCHAR_T);
  36
  37   result = VASNPRINTF (buf, &length, format, args);
  38   if (result == NULL)
  39     return -1;
  40
  41   /* The infinite buffer size guarantees that the result is not malloc()ed.  */
  42   if (result != buf)
  43     {
  44       /* length is near SIZE_MAX.  */
  45       free (result);
  46       errno = EOVERFLOW;
  47       return -1;
  48     }
  49
  50   if (length > INT_MAX)
  51     {
  52       errno = EOVERFLOW;
  53       return -1;
  54     }
  55
  56   /* Return the number of resulting units, excluding the trailing NUL.  */
  57   return length;
  58 }