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/* Copyright (C) 1993-2026 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>.
As a special exception, if you link the code in this file with
files compiled with a GNU compiler to produce an executable,
that does not cause the resulting executable to be covered by
the GNU Lesser General Public License. This exception does not
however invalidate any other reasons why the executable file
might be covered by the GNU Lesser General Public License.
This exception applies to code released by its copyright holders
in files containing the exception. */
#include <stdio.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <libioP.h>
#include <fd_to_filename.h>
#include <shlib-compat.h>
FILE *
freopen (const char *filename, const char *mode, FILE *fp)
{
FILE *result = NULL;
struct fd_to_filename fdfilename;
CHECK_FILE (fp, NULL);
_IO_acquire_lock (fp);
/* First flush the stream (failure should be ignored). */
_IO_SYNC (fp);
if (!(fp->_flags & _IO_IS_FILEBUF))
goto end;
int fd = _IO_fileno (fp);
const char *gfilename
= filename != NULL ? filename : __fd_to_filename (fd, &fdfilename);
fp->_flags2 |= _IO_FLAGS2_NOCLOSE;
#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
if (&_IO_stdin_used == NULL)
{
/* If the shared C library is used by the application binary which
was linked against the older version of libio, we just use the
older one even for internal use to avoid trouble since a pointer
to the old libio may be passed into shared C library and wind
up here. */
_IO_old_file_close_it (fp);
_IO_JUMPS_FUNC_UPDATE (fp, &_IO_old_file_jumps);
fp->_flags2 &= ~(_IO_FLAGS2_MMAP
| _IO_FLAGS2_NOTCANCEL
| _IO_FLAGS2_CLOEXEC);
fp->_mode = 0;
result = _IO_old_file_fopen (fp, gfilename, mode);
}
else
#endif
{
/* Do not unlink the stream because it has to stay on the list.
Flushing through fflush (NULL) is prevented because the
stream is still locked. */
_IO_file_close_maybe_unlink (fp, false);
_IO_JUMPS_FILE_plus (fp) = &_IO_file_jumps;
if (_IO_vtable_offset (fp) == 0 && fp->_wide_data != NULL)
fp->_wide_data->_wide_vtable = &_IO_wfile_jumps;
fp->_flags2 &= ~(_IO_FLAGS2_MMAP
| _IO_FLAGS2_NOTCANCEL
| _IO_FLAGS2_CLOEXEC);
fp->_mode = 0;
result = _IO_file_fopen (fp, gfilename, mode, 1);
if (result != NULL)
result = __fopen_maybe_mmap (result);
}
fp->_flags2 &= ~_IO_FLAGS2_NOCLOSE;
if (result != NULL)
{
if (fd != -1 && _IO_fileno (result) != fd)
{
/* At this point we have both file descriptors already allocated,
so __dup3 will not fail with EBADF, EINVAL, or EMFILE. But
we still need to check for EINVAL and, due Linux internal
implementation, EBUSY. It is because on how it internally opens
the file by splitting the buffer allocation operation and VFS
opening (a dup operation may run when a file is still pending
'install' on VFS). */
if (__dup3 (_IO_fileno (result), fd,
(result->_flags2 & _IO_FLAGS2_CLOEXEC) != 0
? O_CLOEXEC : 0) == -1)
{
_IO_file_close_it (result);
result = NULL;
goto end;
}
__close (_IO_fileno (result));
_IO_fileno (result) = fd;
}
}
else if (fd != -1)
__close (fd);
end:
if (result == NULL)
/* After the unlock below, _IO_flush_all could run and try to
flush the partially closed stream. Setting the flag prevents that. */
fp->_flags2 |= _IO_FLAGS2_NOCLOSE;
_IO_release_lock (fp);
/* See fclose for the concurrency impact. */
if (result == NULL)
{
_IO_un_link ((struct _IO_FILE_plus *) fp);
if (fp->_flags & _IO_IS_FILEBUF)
_IO_deallocate_file (fp);
}
return result;
}
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