Add an option for ignoring EPIPE during close_stdout.

diff --git a/ChangeLog b/ChangeLog
index b5de6d88668b08abf75fe4bc541276c7eeb64d8b..e7db9850979cd13b712e62d1b49808a1f5a7fa1f 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+2008-10-05  Bruno Haible  <bruno@clisp.org>
+            Jim Meyering  <jim@meyering.net>
+
+       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.
+
 2008-10-05  Bruno Haible  <bruno@clisp.org>
 
        * modules/accept: New file.

diff --git a/lib/close-stream.c b/lib/close-stream.c
index e2c3ac0cc4493dfec9710fe68c8a8cc6eeacf6fb..59ab616b1ea43eb3ccef77aed89d13175bec4607 100644 (file)
--- a/lib/close-stream.c
+++ b/lib/close-stream.c
@@ -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

diff --git a/lib/closeout.c b/lib/closeout.c
index 69ddb8b239d80b203c8ce0aaac1983cff27e9ee2..6a0b82ffafd8c4ac7f6192e698227dde11da3296 100644 (file)
--- a/lib/closeout.c
+++ b/lib/closeout.c
@@ -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 +43,43 @@ close_stdout_set_file_name (const char *file)
   file_name = file;
 }
 
+static bool ignore_EPIPE /* = false */;
+
+/* Specify the reaction to an EPIPE error during the closing of stdout:
+     - If ignore = true, it shall be ignored.
+     - If ignore = false, it shall evoke a diagnostic, along with a nonzero
+       exit status.
+   The default is 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 lead to a diagnostic and a nonzero exit status.
+
+   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 lead to a diagnostic message.  */
+
+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 +106,8 @@ close_stdout_set_file_name (const char *file)
 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)

diff --git a/lib/closeout.h b/lib/closeout.h
index fa7adc3113573231a54df3fd879a2141efbc9902..34e61effbfd7c729ebc1f25edb01162d525e9034 100644 (file)
--- a/lib/closeout.h
+++ b/lib/closeout.h
@@ -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

diff --git a/modules/closeout b/modules/closeout
index 4480c7f3ad7ebadad0758e1eed32ac34e56c181c..6a77cef62949833be02b6a0ec36789229ad0ff7d 100644 (file)
--- a/modules/closeout
+++ b/modules/closeout
@@ -12,6 +12,7 @@ gettext-h
 error
 quotearg
 exitfail
+stdbool
 
 configure.ac:
 gl_CLOSEOUT