GNU bug report logs - #22983
syntax-ppss returns wrong result.

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Message #144 received at 22983 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: Alan Mackenzie <acm <at> muc.de>, Philipp Stephani <p.stephani2 <at> gmail.com>,
 22983 <at> debbugs.gnu.org, John Wiegley <jwiegley <at> gmail.com>
Subject: Re: bug#22983: [ Patch ] Re: bug#22983: syntax-ppss returns wrong
 result.
Date: Mon, 11 Sep 2017 07:10:50 -0400

>> I think that (parse-partial-sexp 1 x) is more often what the caller
>> wants than (parse-partial-sexp (point-min) x), but if you're happy with
>> the behavior described by the docstring, then that's fine.
> And yet, I struggle to find such callers.  But those that do, can
> (save-restriction (widen) (syntax-ppss)) anyway.

Good point.

>>> +;; The implementation which follows uses three caches, the current one
>>> +;; (in `syntax-ppss-cache' and `syntax-ppss-last') and two inactive
>>> +;; ones (in `syntax-ppss-{cache,last}-{wide,narrow}'), which store the
>>> +;; former state of the active cache as it was used in widened and
>>> +;; narrowed buffers respectively.
>> Earlier in the thread, I suggested to use a single cache indexed by the
>> position of point-min
> That would lead to clobbering the global cache when we use syntax-ppss for
> some local parsing.

My suggestion is to have a list of N caches, instead of having exactly
2 caches.  I can't see how that could lead to more clobbering.

> I'm considering the idea now that syntax-ppss should stay a caching wrapper
> around parse-partial-sexp, and the responsibility to widen should always be
> the caller's.  This way, it can be used for different purposes that we've
> discussed before many times.

It does have the advantage of circumventing the discussion of
"up-to-where should we widen" ;-)


        Stefan

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