From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeff King <peff@peff.net>
Subject: Re: [PATCH 1/4] run-command: add new check_command helper
Date: Tue, 2 Apr 2013 01:14:07 -0400
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Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
	Johannes Sixt <j6t@kdbg.org>, Aaron Schrab <aaron@schrab.com>,
	Clemens Buchacher <drizzd@aon.at>,
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	Florian Achleitner <florian.achleitner.2.6.31@gmail.com>
To: Felipe Contreras <felipe.contreras@gmail.com>
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On Mon, Apr 01, 2013 at 11:11:20PM -0600, Felipe Contreras wrote:

> > But if we know from reading waitpid(3) that waitpid should only fail due
> > to EINTR, or due to bogus arguments (e.g., a pid that does not exist or
> > has already been reaped), then maybe something like this makes sense:
> >
> >   while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
> >           ; /* nothing */
> 
> But we don't want to wait synchronously here, we just want to ping.

Yeah, sorry, I forgot the WNOHANG there.

> > After the fix above, yes; in the original we would always have exited
> > already.
> 
> No:
> 
> +       if (waiting != cmd->pid)
> +               return 1;
> 
> If waiting < 0, waiting != cmd->pid, and therefore this return is not
> triggered, and there's only one more return at the end of the
> function.

Are my eyes not working? If waiting < 0, then waiting != cmd->pid, and
therefore this return _is_ triggered.

-Peff