Jim Meyering wrote:
> > You can distinguish close_stream and close_stdout. close_stream is library
> > code,
> > close_stdout is not. What about a 'bool ignore_epipe' that influences the
> > behaviour of close_stdout? Whereas the library code that called close_stream
> > has to check against EOF/EPIPE itself if it wants to.
>
> Indeed. This sounds workable, perhaps using a new
> close_stdout_ignore_epipe function.
Here's a proposed patch. The function name 'close_stdout_set_ignore_EPIPE'
was chosen for consistency with the already existing function
'close_stdout_set_file_name'.
2008-10-04 Bruno Haible <[EMAIL PROTECTED]>
Jim Meyering <[EMAIL PROTECTED]>
Add an option for ignoring EPIPE during close_stdout.
* lib/closeout.h: Include <stdbool.h>.
(close_stdout_set_ignore_EPIPE): New declaration.
* lib/closeout.c: Include <stdbool.h>.
(ignore_EPIPE): New variable.
(close_stdout_set_ignore_EPIPE): New function.
(close_stdout): Ignore EPIPE error if ignore_EPIPE is set.
* lib/close-stream.c (close_stream): Mention the possible EPIPE
failure.
* modules/closeout (Depends-on): Add stdbool.
--- lib/closeout.h.orig 2008-10-04 15:01:05.000000000 +0200
+++ lib/closeout.h 2008-10-04 15:00:29.000000000 +0200
@@ -1,6 +1,7 @@
/* Close standard output and standard error.
- Copyright (C) 1998, 2000, 2003, 2004, 2006 Free Software Foundation, Inc.
+ Copyright (C) 1998, 2000, 2003, 2004, 2006, 2008 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
@@ -18,11 +19,14 @@
#ifndef CLOSEOUT_H
# define CLOSEOUT_H 1
+# include <stdbool.h>
+
# ifdef __cplusplus
extern "C" {
# endif
void close_stdout_set_file_name (const char *file);
+void close_stdout_set_ignore_EPIPE (bool ignore);
void close_stdout (void);
# ifdef __cplusplus
--- lib/closeout.c.orig 2008-10-04 15:01:05.000000000 +0200
+++ lib/closeout.c 2008-10-04 14:54:01.000000000 +0200
@@ -1,6 +1,6 @@
/* Close standard output and standard error, exiting with a diagnostic on
error.
- Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004, 2006 Free
+ Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004, 2006, 2008 Free
Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
@@ -21,6 +21,7 @@
#include "closeout.h"
#include <errno.h>
+#include <stdbool.h>
#include <stdio.h>
#include <unistd.h>
@@ -42,6 +43,41 @@
file_name = file;
}
+static bool ignore_EPIPE /* = false */;
+
+/* Specify whether an EPIPE error during the closing of stdout should be
+ ignored (ignore = true) or signaled to the user through an error message
+ (ignore = false).
+
+ This setting matters only if the SIGPIPE signal is ignored (i.e. its
+ handler set to SIG_IGN) or blocked. Only particular programs need to
+ temporarily ignore SIGPIPE. If SIGPIPE is ignored or blocked because
+ it was ignored or blocked in the parent process when it created the
+ child process, it usually is a bug in the parent process: It is bad
+ practice to have SIGPIPE ignored or blocked while creating a child
+ process.
+
+ EPIPE occurs when writing to a pipe or socket that has no readers now,
+ when SIGPIPE is ignored or blocked.
+
+ The ignore = false setting is suitable for a scenario where it is normally
+ guaranteed that the pipe writer terminates before the pipe reader. In
+ this case, an EPIPE is an indication of a premature termination of the
+ pipe reader and should be signaled.
+
+ The ignore = true setting is suitable for a scenario where you don't know
+ ahead of time whether the pipe writer or the pipe reader will terminate
+ first. In this case, an EPIPE is an indication that the pipe writer can
+ stop doing useless write() calls; this is what close_stdout does anyway.
+ EPIPE is part of the normal pipe/socket shutdown protocol in this case,
+ and should not be signaled. */
+
+void
+close_stdout_set_ignore_EPIPE (bool ignore)
+{
+ ignore_EPIPE = ignore;
+}
+
/* Close standard output. On error, issue a diagnostic and _exit
with status 'exit_failure'.
@@ -68,7 +104,8 @@
void
close_stdout (void)
{
- if (close_stream (stdout) != 0)
+ if (close_stream (stdout) != 0
+ && !(ignore_EPIPE && errno == EPIPE))
{
char const *write_error = _("write error");
if (file_name)
--- lib/close-stream.c.orig 2008-10-04 15:01:05.000000000 +0200
+++ lib/close-stream.c 2008-10-04 14:58:09.000000000 +0200
@@ -1,6 +1,6 @@
/* Close a stream, with nicer error checking than fclose's.
- Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004, 2006, 2007 Free
+ Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004, 2006, 2007, 2008 Free
Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
@@ -33,6 +33,10 @@
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
--- modules/closeout.orig 2008-10-04 15:01:05.000000000 +0200
+++ modules/closeout 2008-10-04 14:18:32.000000000 +0200
@@ -12,6 +12,7 @@
error
quotearg
exitfail
+stdbool
configure.ac:
gl_CLOSEOUT
