/* Close a stream, with nicer error checking than fclose's.

   Copyright (C) 1998-2002, 2004, 2006-2017 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include <config.h>

#include "close-stream.h"

#include <errno.h>

#include <stdbool.h>

#include "fpending.h"

#if USE_UNLOCKED_IO

# include "unlocked-io.h"

#endif

/* Close STREAM.  Return 0 if successful, EOF (setting errno)

   otherwise.  A failure might set errno to 0 if the error number

   cannot be determined.

   A failure with errno set to EPIPE may or may not indicate an error

   situation worth signaling to the user.  See the documentation of the

   close_stdout_set_ignore_EPIPE function for details.

   If a program writes *anything* to STREAM, that program should close

   STREAM and make sure that it succeeds before exiting.  Otherwise,

   suppose that you go to the extreme of checking the return status

   of every function that does an explicit write to STREAM.  The last

   printf can succeed in writing to the internal stream buffer, and yet

   the fclose(STREAM) could still fail (due e.g., to a disk full error)

   when it tries to write out that buffered data.  Thus, you would be

   left with an incomplete output file and the offending program would

   exit successfully.  Even calling fflush is not always sufficient,

   since some file systems (NFS and CODA) buffer written/flushed data

   until an actual close call.

   Besides, it's wasteful to check the return value from every call

   that writes to STREAM -- just let the internal stream state record

   the failure.  That's what the ferror test is checking below.  */

int

close_stream (FILE *stream)

{

  const bool some_pending = (__fpending (stream) != 0);

  const bool prev_fail = (ferror (stream) != 0);

  const bool fclose_fail = (fclose (stream) != 0);

  /* Return an error indication if there was a previous failure or if

     fclose failed, with one exception: ignore an fclose failure if

     there was no previous error, no data remains to be flushed, and

     fclose failed with EBADF.  That can happen when a program like cp

     is invoked like this 'cp a b >&-' (i.e., with standard output

     closed) and doesn't generate any output (hence no previous error

     and nothing to be flushed).  */

  if (prev_fail || (fclose_fail && (some_pending || errno != EBADF)))

    {

      if (! fclose_fail)

        errno = 0;

      return EOF;

    }

  return 0;

}