Add an option for ignoring EPIPE during close_stdout.

1 files changed, 41 insertions, 2 deletions

diff --git a/lib/closeout.c b/lib/closeout.c
index 69ddb8b239..6a0b82ffaf 100644
--- 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)