1  /* closeout.c - close standard output and standard error
       2     Copyright (C) 1998-2007, 2012 Free Software Foundation, Inc.
       3  
       4     This program is free software: you can redistribute it and/or modify
       5     it under the terms of the GNU General Public License as published by
       6     the Free Software Foundation; either version 3 of the License, or
       7     (at your option) any later version.
       8  
       9     This program 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
      12     GNU General Public License for more details.
      13  
      14     You should have received a copy of the GNU General Public License
      15     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      16  
      17  #include <config.h>
      18  
      19  /* Specification.  */
      20  #include "closeout.h"
      21  
      22  #include <stdio.h>
      23  #include <stdlib.h>
      24  #include <errno.h>
      25  
      26  #include "error.h"
      27  #include "fwriteerror.h"
      28  #include "gettext.h"
      29  
      30  #define _(msgid) gettext (msgid)
      31  
      32  /* Close standard output, exiting with status STATUS on failure.
      33     If a program writes *anything* to stdout, that program should close
      34     stdout and make sure that it succeeds before exiting.  Otherwise,
      35     suppose that you go to the extreme of checking the return status
      36     of every function that does an explicit write to stdout.  The last
      37     printf can succeed in writing to the internal stream buffer, and yet
      38     the fclose(stdout) could still fail (due e.g., to a disk full error)
      39     when it tries to write out that buffered data.  Thus, you would be
      40     left with an incomplete output file and the offending program would
      41     exit successfully.  Even calling fflush is not always sufficient,
      42     since some file systems (NFS and CODA) buffer written/flushed data
      43     until an actual close call.
      44  
      45     Besides, it's wasteful to check the return value from every call
      46     that writes to stdout -- just let the internal stream state record
      47     the failure.  That's what the ferror test is checking below.
      48  
      49     If the stdout file descriptor was initially closed (such as when executing
      50     a program through "program 1>&-"), it is a failure if and only if some
      51     output was made to stdout.
      52  
      53     Likewise for standard error.
      54  
      55     It's important to detect such failures and exit nonzero because many
      56     tools (most notably 'make' and other build-management systems) depend
      57     on being able to detect failure in other tools via their exit status.  */
      58  
      59  /* Close standard output and standard error, exiting with status EXIT_FAILURE
      60     on failure.  */
      61  void
      62  close_stdout (void)
      63  {
      64    /* Close standard output.  */
      65    if (fwriteerror_no_ebadf (stdout))
      66      error (EXIT_FAILURE, errno, "%s", _("write error"));
      67  
      68    /* Close standard error.  This is simpler than fwriteerror_no_ebadf, because
      69       upon failure we don't need an errno - all we can do at this point is to
      70       set an exit status.  */
      71    errno = 0;
      72    if (ferror (stderr) || fflush (stderr))
      73      {
      74        fclose (stderr);
      75        exit (EXIT_FAILURE);
      76      }
      77    if (fclose (stderr) && errno != EBADF)
      78      exit (EXIT_FAILURE);
      79  }
      80  
      81  /* Note: When exit (...) calls the atexit-registered
      82                close_stdout (), which calls
      83                error (status, ...), which calls
      84                exit (status),
      85     we have undefined behaviour according to ISO C 99 section 7.20.4.3.(2).
      86     But in practice there is no problem: The second exit call is executed
      87     at a moment when the atexit handlers are no longer active.  */