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glibc  2.9
gets_chk.c
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00001 /* Copyright (C) 1993, 1996, 1997, 1998, 2002, 2003, 2004
00002    Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.
00019 
00020    As a special exception, if you link the code in this file with
00021    files compiled with a GNU compiler to produce an executable,
00022    that does not cause the resulting executable to be covered by
00023    the GNU Lesser General Public License.  This exception does not
00024    however invalidate any other reasons why the executable file
00025    might be covered by the GNU Lesser General Public License.
00026    This exception applies to code released by its copyright holders
00027    in files containing the exception.  */
00028 
00029 #include "../libio/libioP.h"
00030 #include <limits.h>
00031 
00032 char *
00033 __gets_chk (char *buf, size_t size)
00034 {
00035   _IO_size_t count;
00036   int ch;
00037   char *retval;
00038 
00039   if (size == 0)
00040     __chk_fail ();
00041 
00042   _IO_acquire_lock (_IO_stdin);
00043   ch = _IO_getc_unlocked (_IO_stdin);
00044   if (ch == EOF)
00045     {
00046       retval = NULL;
00047       goto unlock_return;
00048     }
00049   if (ch == '\n')
00050     count = 0;
00051   else
00052     {
00053       /* This is very tricky since a file descriptor may be in the
00054         non-blocking mode. The error flag doesn't mean much in this
00055         case. We return an error only when there is a new error. */
00056       int old_error = _IO_stdin->_IO_file_flags & _IO_ERR_SEEN;
00057       _IO_stdin->_IO_file_flags &= ~_IO_ERR_SEEN;
00058       buf[0] = (char) ch;
00059       count = INTUSE(_IO_getline) (_IO_stdin, buf + 1, size - 1, '\n', 0) + 1;
00060       if (_IO_stdin->_IO_file_flags & _IO_ERR_SEEN)
00061        {
00062          retval = NULL;
00063          goto unlock_return;
00064        }
00065       else
00066        _IO_stdin->_IO_file_flags |= old_error;
00067     }
00068   if (count >= size)
00069     __chk_fail ();
00070   buf[count] = 0;
00071   retval = buf;
00072 unlock_return:
00073   _IO_release_lock (_IO_stdin);
00074   return retval;
00075 }
00076 
00077 link_warning (__gets_chk, "the `gets' function is dangerous and should not be used.")