Re: [PATCH v3 08/19] write_or_die: raise SIGPIPE when we get EPIPE

From: Jeff King <peff@peff.net>
Date: Feb 20, 2013, 22:12 UTC
Message-ID: <20130220221248.GC817@sigill.intra.peff.net>
In-Reply-To: <20130220220637.GC24236@google.com>

On Wed, Feb 20, 2013 at 02:06:37PM -0800, Jonathan Nieder wrote:

Show 8 quoted lines

> > I don't mind adding a "BUG: " message like you described, but we should
> > still try to exit(141) as the backup, since that is the shell-equivalent
> > code to the SIGPIPE signal death.
> 
> If you want. :)
> 
> I think caring about graceful degradation of behavior in the case of
> an assertion failure is overengineering, but it's mostly harmless.

I am more concerned that the assertion is not "oops, another thread is doing something crazy, and it is a bug", but rather that there is some weird platform where SIG_DFL does not kill the program under SIGPIPE. That seems pretty crazy, though. I think I'd squash in something like this:

diff --git a/write_or_die.c b/write_or_die.c
index b50f99a..abb64db 100644
--- a/write_or_die.c
+++ b/write_or_die.c
@@ -5,7 +5,9 @@ static void check_pipe(int err)
 	if (err == EPIPE) {
 		signal(SIGPIPE, SIG_DFL);
 		raise(SIGPIPE);
+
 		/* Should never happen, but just in case... */
+		error("BUG: SIGPIPE on SIG_DFL handler did not kill us.");
 		exit(141);
 	}
 }

which more directly reports the assertion that failed, and degrades
reasonably gracefully. Yeah, it's probably overengineering, but it's
easy enough to do.

-Peff