libio/freopen.c

   1 /* Copyright (C) 1993,95,96,97,98,2000,2001,2002,2003,2008,2011
   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 "libioP.h"
  29 #include "stdio.h"
  30 #include <fcntl.h>
  31 #include <stdlib.h>
  32 #include <unistd.h>
  33
  34 #include <shlib-compat.h>
  35 #include <fd_to_filename.h>
  36
  37 FILE*
  38 freopen (filename, mode, fp)
  39      const char* filename;
  40      const char* mode;
  41      FILE* fp;
  42 {
  43   FILE *result;
  44   CHECK_FILE (fp, NULL);
  45   if (!(fp->_flags & _IO_IS_FILEBUF))
  46     return NULL;
  47   _IO_acquire_lock (fp);
  48   int fd = _IO_fileno (fp);
  49   const char *gfilename = (filename == NULL && fd >= 0
  50                            ? fd_to_filename (fd) : filename);
  51   fp->_flags2 |= _IO_FLAGS2_NOCLOSE;
  52 #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
  53   if (&_IO_stdin_used == NULL)
  54     {
  55       /* If the shared C library is used by the application binary which
  56          was linked against the older version of libio, we just use the
  57          older one even for internal use to avoid trouble since a pointer
  58          to the old libio may be passed into shared C library and wind
  59          up here. */
  60       _IO_old_file_close_it (fp);
  61       _IO_JUMPS ((struct _IO_FILE_plus *) fp) = &_IO_old_file_jumps;
  62       result = _IO_old_file_fopen (fp, gfilename, mode);
  63     }
  64   else
  65 #endif
  66     {
  67       INTUSE(_IO_file_close_it) (fp);
  68       _IO_JUMPS ((struct _IO_FILE_plus *) fp) = &_IO_file_jumps;
  69       if (_IO_vtable_offset (fp) == 0 && fp->_wide_data != NULL)
  70         fp->_wide_data->_wide_vtable = &_IO_wfile_jumps;
  71       result = INTUSE(_IO_file_fopen) (fp, gfilename, mode, 1);
  72       if (result != NULL)
  73         result = __fopen_maybe_mmap (result);
  74     }
  75   fp->_flags2 &= ~_IO_FLAGS2_NOCLOSE;
  76   if (result != NULL)
  77     {
  78       /* unbound stream orientation */
  79       result->_mode = 0;
  80
  81       if (fd != -1)
  82         {
  83 #ifdef O_CLOEXEC
  84 # ifndef __ASSUME_DUP3
  85           int newfd;
  86           if (__have_dup3 < 0)
  87             newfd = -1;
  88           else
  89             newfd =
  90 # endif
  91               dup3 (_IO_fileno (result), fd,
  92                     (result->_flags2 & _IO_FLAGS2_CLOEXEC) != 0
  93                     ? O_CLOEXEC : 0);
  94 #else
  95 # define newfd 1
  96 #endif
  97
  98 #ifndef __ASSUME_DUP3
  99           if (newfd < 0)
 100             {
 101               if (errno == ENOSYS)
 102                 __have_dup3 = -1;
 103
 104               __dup2 (_IO_fileno (result), fd);
 105               if ((result->_flags2 & _IO_FLAGS2_CLOEXEC) != 0)
 106                 __fcntl (fd, F_SETFD, FD_CLOEXEC);
 107             }
 108 #endif
 109           __close (_IO_fileno (result));
 110           _IO_fileno (result) = fd;
 111         }
 112     }
 113   else if (fd != -1)
 114     __close (fd);
 115   if (filename == NULL)
 116     free ((char *) gfilename);
 117
 118   _IO_release_lock (fp);
 119   return result;
 120 }