debug/vasprintf_chk.c

   1 /* Copyright (C) 1995,1997,1999-2002,2004,2006,2008,2009
   2    Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.
  18
  19    As a special exception, if you link the code in this file with
  20    files compiled with a GNU compiler to produce an executable,
  21    that does not cause the resulting executable to be covered by
  22    the GNU Lesser General Public License.  This exception does not
  23    however invalidate any other reasons why the executable file
  24    might be covered by the GNU Lesser General Public License.
  25    This exception applies to code released by its copyright holders
  26    in files containing the exception.  */
  27
  28 #include <malloc.h>
  29 #include <string.h>
  30 #include <stdio.h>
  31 #include <stdio_ext.h>
  32 #include "../libio/libioP.h"
  33 #include "../libio/strfile.h"
  34
  35 int
  36 __vasprintf_chk (char **result_ptr, int flags, const char *format,
  37                  va_list args)
  38 {
  39   /* Initial size of the buffer to be used.  Will be doubled each time an
  40      overflow occurs.  */
  41   const _IO_size_t init_string_size = 100;
  42   char *string;
  43   _IO_strfile sf;
  44   int ret;
  45   _IO_size_t needed;
  46   _IO_size_t allocated;
  47   /* No need to clear the memory here (unlike for open_memstream) since
  48      we know we will never seek on the stream.  */
  49   string = (char *) malloc (init_string_size);
  50   if (string == NULL)
  51     return -1;
  52 #ifdef _IO_MTSAFE_IO
  53   sf._sbf._f._lock = NULL;
  54 #endif
  55   _IO_no_init (&sf._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
  56   _IO_JUMPS (&sf._sbf) = &_IO_str_jumps;
  57   _IO_str_init_static_internal (&sf, string, init_string_size, string);
  58   sf._sbf._f._flags &= ~_IO_USER_BUF;
  59   sf._s._allocate_buffer = (_IO_alloc_type) malloc;
  60   sf._s._free_buffer = (_IO_free_type) free;
  61
  62   /* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
  63      can only come from read-only format strings.  */
  64   if (flags > 0)
  65     sf._sbf._f._flags2 |= _IO_FLAGS2_FORTIFY;
  66
  67   ret = INTUSE(_IO_vfprintf) (&sf._sbf._f, format, args);
  68   if (ret < 0)
  69     {
  70       free (sf._sbf._f._IO_buf_base);
  71       return ret;
  72     }
  73   /* Only use realloc if the size we need is of the same (binary)
  74      order of magnitude then the memory we allocated.  */
  75   needed = sf._sbf._f._IO_write_ptr - sf._sbf._f._IO_write_base + 1;
  76   allocated = sf._sbf._f._IO_write_end - sf._sbf._f._IO_write_base;
  77   if ((allocated >> 1) <= needed)
  78     *result_ptr = (char *) realloc (sf._sbf._f._IO_buf_base, needed);
  79   else
  80     {
  81       *result_ptr = (char *) malloc (needed);
  82       if (*result_ptr != NULL)
  83         {
  84           memcpy (*result_ptr, sf._sbf._f._IO_buf_base, needed - 1);
  85           free (sf._sbf._f._IO_buf_base);
  86         }
  87       else
  88         /* We have no choice, use the buffer we already have.  */
  89         *result_ptr = (char *) realloc (sf._sbf._f._IO_buf_base, needed);
  90     }
  91   if (*result_ptr == NULL)
  92     *result_ptr = sf._sbf._f._IO_buf_base;
  93   (*result_ptr)[needed - 1] = '\0';
  94   return ret;
  95 }
  96 libc_hidden_def (__vasprintf_chk)