GNU bug report logs - #42147
28.0.50; pure vs side-effect-free, missing optimizations?

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Package: emacs;

Reported by: Andrea Corallo <andrea_corallo <at> yahoo.it>

Date: Tue, 30 Jun 2020 22:28:02 UTC

Severity: normal

Found in version 28.0.50

Done: Mattias Engdegård <mattiase <at> acm.org>

Bug is archived. No further changes may be made.

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Message #265 received at 42147 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Mattias Engdegård <mattiase <at> acm.org>
Cc: Philipp Stephani <p.stephani2 <at> gmail.com>, Paul Eggert <eggert <at> cs.ucla.edu>,
 Andrea Corallo <andrea_corallo <at> yahoo.it>, 42147 <at> debbugs.gnu.org
Subject: Re: bug#42147: 28.0.50; pure vs side-effect-free, missing
 optimizations?
Date: Sat, 25 Jul 2020 18:30:10 -0400

>>> There are also some functions declared 'pure' that appear to have side
>>> effects: kbd, package-get-version
>> Which side-effects are you thinking of?
> They both clobber the match data.

It's not a problem w.r.t optimizing pure functions, tho: those functions
don't promise to modify the match data, so it's OK to replace calls to
them with their return value.

But yes, it's a problem because `C-h o kbd RET` says explicitly that it
doesn't change the match data :-(


        Stefan
This bug report was last modified 4 years and 281 days ago.

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