1  /* Copyright (C) 1993-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library 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
      15     License along with the GNU C Library; if not, see
      16     <https://www.gnu.org/licenses/>.
      17  
      18     As a special exception, if you link the code in this file with
      19     files compiled with a GNU compiler to produce an executable,
      20     that does not cause the resulting executable to be covered by
      21     the GNU Lesser General Public License.  This exception does not
      22     however invalidate any other reasons why the executable file
      23     might be covered by the GNU Lesser General Public License.
      24     This exception applies to code released by its copyright holders
      25     in files containing the exception.  */
      26  
      27  #include <stdio.h>
      28  #include <fcntl.h>
      29  #include <stdlib.h>
      30  #include <unistd.h>
      31  
      32  #include <libioP.h>
      33  #include <fd_to_filename.h>
      34  #include <shlib-compat.h>
      35  
      36  FILE *
      37  freopen (const char *filename, const char *mode, FILE *fp)
      38  {
      39    FILE *result = NULL;
      40    struct fd_to_filename fdfilename;
      41  
      42    CHECK_FILE (fp, NULL);
      43  
      44    _IO_acquire_lock (fp);
      45    /* First flush the stream (failure should be ignored).  */
      46    _IO_SYNC (fp);
      47  
      48    if (!(fp->_flags & _IO_IS_FILEBUF))
      49      goto end;
      50  
      51    int fd = _IO_fileno (fp);
      52    const char *gfilename
      53      = filename != NULL ? filename : __fd_to_filename (fd, &fdfilename);
      54  
      55    fp->_flags2 |= _IO_FLAGS2_NOCLOSE;
      56  #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
      57    if (&_IO_stdin_used == NULL)
      58      {
      59        /* If the shared C library is used by the application binary which
      60  	 was linked against the older version of libio, we just use the
      61  	 older one even for internal use to avoid trouble since a pointer
      62  	 to the old libio may be passed into shared C library and wind
      63  	 up here. */
      64        _IO_old_file_close_it (fp);
      65        _IO_JUMPS_FUNC_UPDATE (fp, &_IO_old_file_jumps);
      66        result = _IO_old_file_fopen (fp, gfilename, mode);
      67      }
      68    else
      69  #endif
      70      {
      71        _IO_file_close_it (fp);
      72        _IO_JUMPS_FILE_plus (fp) = &_IO_file_jumps;
      73        if (_IO_vtable_offset (fp) == 0 && fp->_wide_data != NULL)
      74  	fp->_wide_data->_wide_vtable = &_IO_wfile_jumps;
      75        result = _IO_file_fopen (fp, gfilename, mode, 1);
      76        if (result != NULL)
      77  	result = __fopen_maybe_mmap (result);
      78      }
      79    fp->_flags2 &= ~_IO_FLAGS2_NOCLOSE;
      80    if (result != NULL)
      81      {
      82        /* unbound stream orientation */
      83        result->_mode = 0;
      84  
      85        if (fd != -1 && _IO_fileno (result) != fd)
      86  	{
      87  	  /* At this point we have both file descriptors already allocated,
      88  	     so __dup3 will not fail with EBADF, EINVAL, or EMFILE.  But
      89  	     we still need to check for EINVAL and, due Linux internal
      90  	     implementation, EBUSY.  It is because on how it internally opens
      91  	     the file by splitting the buffer allocation operation and VFS
      92  	     opening (a dup operation may run when a file is still pending
      93  	     'install' on VFS).  */
      94  	  if (__dup3 (_IO_fileno (result), fd,
      95  		      (result->_flags2 & _IO_FLAGS2_CLOEXEC) != 0
      96  		      ? O_CLOEXEC : 0) == -1)
      97  	    {
      98  	      _IO_file_close_it (result);
      99  	      result = NULL;
     100  	      goto end;
     101  	    }
     102  	  __close (_IO_fileno (result));
     103  	  _IO_fileno (result) = fd;
     104  	}
     105      }
     106    else if (fd != -1)
     107      __close (fd);
     108  
     109  end:
     110    _IO_release_lock (fp);
     111    return result;
     112  }