lib/closeout.c

   1 /* Close standard output and standard error, exiting with a diagnostic on error.
   2
   3    Copyright (C) 1998-2002, 2004, 2006, 2008-2024 Free Software Foundation,
   4    Inc.
   5
   6    This program is free software: you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation, either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  18
  19 #include <config.h>
  20
  21 #include "closeout.h"
  22
  23 #include <errno.h>
  24 #include <stdio.h>
  25 #include <unistd.h>
  26
  27 #include "gettext.h"
  28 #define _(msgid) gettext (msgid)
  29
  30 #include "close-stream.h"
  31 #include <error.h>
  32 #include "exitfail.h"
  33 #include "quotearg.h"
  34
  35 #ifndef __has_feature
  36 # define __has_feature(a) false
  37 #endif
  38
  39 #if defined __SANITIZE_ADDRESS__ || __has_feature (address_sanitizer)
  40 enum { SANITIZE_ADDRESS = true };
  41 #else
  42 enum { SANITIZE_ADDRESS = false };
  43 #endif
  44
  45 static const char *file_name;
  46
  47 /* Set the file name to be reported in the event an error is detected
  48    by close_stdout.  */
  49 void
  50 close_stdout_set_file_name (const char *file)
  51 {
  52   file_name = file;
  53 }
  54
  55 static bool ignore_EPIPE /* = false */;
  56
  57 /* Specify the reaction to an EPIPE error during the closing of stdout:
  58      - If ignore = true, it shall be ignored.
  59      - If ignore = false, it shall evoke a diagnostic, along with a nonzero
  60        exit status.
  61    The default is ignore = false.
  62
  63    This setting matters only if the SIGPIPE signal is ignored (i.e. its
  64    handler set to SIG_IGN) or blocked.  Only particular programs need to
  65    temporarily ignore SIGPIPE.  If SIGPIPE is ignored or blocked because
  66    it was ignored or blocked in the parent process when it created the
  67    child process, it usually is a bug in the parent process: It is bad
  68    practice to have SIGPIPE ignored or blocked while creating a child
  69    process.
  70
  71    EPIPE occurs when writing to a pipe or socket that has no readers now,
  72    when SIGPIPE is ignored or blocked.
  73
  74    The ignore = false setting is suitable for a scenario where it is normally
  75    guaranteed that the pipe writer terminates before the pipe reader.  In
  76    this case, an EPIPE is an indication of a premature termination of the
  77    pipe reader and should lead to a diagnostic and a nonzero exit status.
  78
  79    The ignore = true setting is suitable for a scenario where you don't know
  80    ahead of time whether the pipe writer or the pipe reader will terminate
  81    first.  In this case, an EPIPE is an indication that the pipe writer can
  82    stop doing useless write() calls; this is what close_stdout does anyway.
  83    EPIPE is part of the normal pipe/socket shutdown protocol in this case,
  84    and should not lead to a diagnostic message.  */
  85
  86 void
  87 close_stdout_set_ignore_EPIPE (bool ignore)
  88 {
  89   ignore_EPIPE = ignore;
  90 }
  91
  92 /* Close standard output.  On error, issue a diagnostic and _exit
  93    with status 'exit_failure'.
  94
  95    Also close standard error.  On error, _exit with status 'exit_failure'.
  96
  97    Since close_stdout is commonly registered via 'atexit', POSIX
  98    and the C standard both say that it should not call 'exit',
  99    because the behavior is undefined if 'exit' is called more than
 100    once.  So it calls '_exit' instead of 'exit'.  If close_stdout
 101    is registered via atexit before other functions are registered,
 102    the other functions can act before this _exit is invoked.
 103
 104    Applications that use close_stdout should flush any streams
 105    other than stdout and stderr before exiting, since the call to
 106    _exit will bypass other buffer flushing.  Applications should
 107    be flushing and closing other streams anyway, to check for I/O
 108    errors.  Also, applications should not use tmpfile, since _exit
 109    can bypass the removal of these files.
 110
 111    It's important to detect such failures and exit nonzero because many
 112    tools (most notably 'make' and other build-management systems) depend
 113    on being able to detect failure in other tools via their exit status.  */
 114
 115 void
 116 close_stdout (void)
 117 {
 118   if (close_stream (stdout) != 0
 119       && !(ignore_EPIPE && errno == EPIPE))
 120     {
 121       char const *write_error = _("write error");
 122       if (file_name)
 123         error (0, errno, "%s: %s", quotearg_colon (file_name),
 124                write_error);
 125       else
 126         error (0, errno, "%s", write_error);
 127
 128       _exit (exit_failure);
 129     }
 130
 131   /* Close stderr only if not sanitizing, as sanitizers may report to
 132      stderr after this function returns.  */
 133   if (!SANITIZE_ADDRESS && close_stream (stderr) != 0)
 134     _exit (exit_failure);
 135 }