From: Tomi Ollila <tomi.ollila@iki.fi>
To: Austin Clements <amdragon@MIT.EDU>,
	Mark Walters <markwalters1009@gmail.com>
Subject: Re: [PATCH 2/2] emacs: Fix "no such file or directory" error
In-Reply-To: <20130610021534.GB22196@mit.edu>
References: <1370753138-15021-1-git-send-email-amdragon@mit.edu>
	<1370753138-15021-3-git-send-email-amdragon@mit.edu>
	<87hah7od8b.fsf@qmul.ac.uk> <20130610021534.GB22196@mit.edu>
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	(x86_64-unknown-linux-gnu)
Date: Mon, 10 Jun 2013 09:21:29 +0300
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On Mon, Jun 10 2013, Austin Clements <amdragon@MIT.EDU> wrote:

> Quoth Mark Walters on Jun 09 at 10:16 am:
>> 
>> Both of these patches look good to me +1. I was able to reproduce both
>> bugs pretty reliably (the first one always unless masked by the second
>> one which occurred about half the time). With these patches I cannot
>> trigger either. Also all tests pass.
>> 
>> My only tiny concern is I couldn't find any documentation on whether the
>> return value of the filter-function matters at all. Austin's original
>> fix (via irc) returned t and this returns nil in the failing case (i.e.,
>> when results-buf is dead).
>
> Mm, interesting.  To be fair, my choice of "t" for the original fix
> was completely arbitrary.  I think you're right that the Emacs
> documentation doesn't have anything to say about the return values of
> filter functions.  Furthermore, the example filter functions they give
> don't have meaningful return values, so I'm pretty sure this is safe.
> Also the code that calls the filter discards its result.

I also looked this a bit yesterday evening. For example this page

http://www.gnu.org/software/emacs/manual/html_node/elisp/Filter-Functions.html

discusses only about catching thrown errors -- i.e. no mention about
filter function return values. From that I'd draw a conclusion that 
most probably the return value of filter function is not used for anything.

... and the patch looks good. +1 (removing needs-review)

Tomi