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From: Dmitry Gutov <dgutov@yandex.ru>
To: Alan Mackenzie <acm@muc.de>
Cc: 22983@debbugs.gnu.org
Subject: bug#22983: syntax-ppss returns wrong result.
Date: Sat, 12 Mar 2016 00:38:49 +0200	[thread overview]
Message-ID: <2c301ec9-041d-9172-d628-479062314b23@yandex.ru> (raw)
In-Reply-To: <20160311221540.GH2888@acm.fritz.box>

On 03/12/2016 12:15 AM, Alan Mackenzie wrote:

>> That part of specification can be rephrased.
>
> It's more than the specification which needs redoing.  The implementation
> (sometimes) returns the equivalent of (parse-partial-sexp (point-min)
> pos)), when point-min is not in a "safe place".

Sure. I just meant that we shouldn't get hung up on that element of the 
specification.

>>>> Changing syntax-ppss to be independent of narrowing will break it, and
>>>> we'll need to provide some alternative first.
>
>>> syntax-ppss is broken, and can't be fixed.
>
>> It's used ubiquitously, so it must be working.
>
> It might well be ubiquitous, but it's broken.

And yet, it can be fixed.

> Consider this: syntax-ppss
> will return the result of a parse based at point-min.  In general, the
> caller does not know whether point-min is in a string or not.  Therefore
> the result is of little value, UNLESS the caller takes special action,
> such as widening the buffer before every call to syntax-ppss.

You can say that.

>> Not entirely different, no. AFAIK, these are the semantics the vast
>> majority of its usages expect.
>
> But it's not the semantics these .el files get.  What's probably keeping
> them functional is the rarity with which buffers are narrowed to an
> "awkward" point-min.

Another thing that keeps it together, is that narrowing, as a user-level 
operator, is not that popular.

Personally, I consider it an anti-feature.

>> Except the multiple-major-mode case, which we'd ideally try to
>> accommodate, too.
>
> How does this code handle the changeover of syntax tables at a mode
> boundary?

The "inner" regions start with an "empty", top-level state. This is 
actually fine, because these are usually small enough not to benefit 
from the syntax-ppss cache too much (and syntax-ppss-last still helps).

The parts of the outer region following a subregion with different 
syntax table... rely on a few hacks, and a manual application of a 
`syntax-table' property when necessary. We need a better solution there, 
but it's probably out of scope for this discussion.

>> syntax-ppss-dont-widen would be nil by default, it would be an escape
>> hatch toward the current semantics, for when the caller knows how to
>> manage narrowings, etc.
>
> Ah, OK.  I think I see that now.  Maybe.  Surely the trouble is that
> either ALL calls or NONE must have s-p-dont-widen set.

Hmm, you're right. This variable still seems essential, but to be safe, 
mmm-mode and friends should probably also advise syntax-ppss, to always 
perform narrowing as appropriate.

> When that flag is
> toggled, all the caches have to be cleared.  Maybe there should be some
> initialisation flag in some initialisation function.  Or something like
> that.  (It's getting late!).

Is the syntax-ppss-dont-widen really relevant for your comment cache? It 
would be used only by certain major modes, and worst comes to worst, you 
could disable the cache in those buffers.

> It strikes me that the multiple major mode stuff could do with a
> substantially enhanced version of syntax-ppss which would smoothly handle
> going over a mode boundary.  But I don't know how you're implementing
> that.

So far, we're just wrapping the font-lock and indentation code, and 
otherwise hope for the best.





  reply	other threads:[~2016-03-11 22:38 UTC|newest]

Thread overview: 155+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-11 15:15 bug#22983: syntax-ppss returns wrong result Alan Mackenzie
2016-03-11 20:31 ` Dmitry Gutov
2016-03-11 21:24   ` Alan Mackenzie
2016-03-11 21:35     ` Dmitry Gutov
2016-03-11 22:15       ` Alan Mackenzie
2016-03-11 22:38         ` Dmitry Gutov [this message]
2016-03-13 17:37           ` Stefan Monnier
2016-03-13 18:57             ` Alan Mackenzie
2016-03-14  0:47               ` Dmitry Gutov
2016-03-14  1:04                 ` Drew Adams
2016-04-03 22:55                   ` John Wiegley
2016-03-14  1:49               ` Stefan Monnier
2016-03-14 15:16           ` Syntax tables for multiple modes [was: bug#22983: syntax-ppss returns wrong result.] Alan Mackenzie
2016-03-14 17:34             ` Andreas Röhler
2016-03-14 20:06             ` Dmitry Gutov
2016-03-19 22:51               ` Vitalie Spinu
2016-03-20  2:19                 ` Dmitry Gutov
2016-03-20 12:15                   ` Vitalie Spinu
2016-03-20 15:58                     ` Dmitry Gutov
2016-03-21  1:05                       ` Vitalie Spinu
2016-03-21  3:11                         ` Stefan Monnier
2016-03-21  5:05                           ` Vitalie Spinu
2016-03-21  7:13                             ` Andreas Röhler
2016-03-21 12:26                             ` Stefan Monnier
2016-03-21 14:13                               ` Vitalie Spinu
2016-03-21 14:43                                 ` Stefan Monnier
2016-03-21 16:42                                   ` Vitalie Spinu
2016-03-21 18:31                                     ` Stefan Monnier
2016-03-21 19:16                                       ` Vitalie Spinu
2016-03-21 20:47                                         ` Stefan Monnier
2016-03-21 20:33                                     ` Alan Mackenzie
2016-03-21 20:49                                       ` Stefan Monnier
2016-03-21 21:03                                       ` Drew Adams
2016-03-21 21:12                                       ` Dmitry Gutov
2016-03-21 16:45                                   ` Vitalie Spinu
2016-03-21 22:55                                     ` Dmitry Gutov
2016-03-22 14:51                                     ` Stefan Monnier
2016-03-22 18:17                                       ` Vitalie Spinu
2016-03-23  1:18                                         ` Dmitry Gutov
2016-03-23 13:18                                         ` Stefan Monnier
2016-03-22 18:26                                       ` Vitalie Spinu
2016-03-23  2:07                                         ` Stefan Monnier
2016-03-23 10:56                                           ` Vitalie Spinu
2016-03-23 11:41                                             ` Stefan Monnier
2016-03-23 12:39                                               ` Vitalie Spinu
2016-03-23 13:23                                                 ` Stefan Monnier
2016-03-23 15:28                                                   ` Dmitry Gutov
2016-03-23 21:51                                                     ` Vitalie Spinu
2016-03-24  7:30                                               ` Andreas Röhler
2016-03-21 11:56                           ` Dmitry Gutov
2016-03-21  5:08                         ` [Patch] hard-widen-limits [was Re: Syntax tables for multiple modes [was: bug#22983: syntax-ppss returns wrong result.]] Vitalie Spinu
2016-03-21 12:39                           ` Stefan Monnier
2016-03-21 12:54                             ` Vitalie Spinu
2016-03-21 14:07                               ` Stefan Monnier
2016-03-21 14:14                                 ` Vitalie Spinu
2016-03-21 14:04                             ` Stefan Monnier
2016-03-21 14:33                               ` Vitalie Spinu
2016-03-21 14:54                                 ` Stefan Monnier
2016-03-21 17:16                                   ` Vitalie Spinu
2016-03-21 18:36                                     ` Stefan Monnier
2016-03-21 19:18                                       ` Vitalie Spinu
2016-03-22  3:17                                         ` Vitalie Spinu
2016-03-22  9:57                                           ` Vitalie Spinu
2016-03-22 10:05                                             ` Vitalie Spinu
2016-03-22 11:57                                               ` Stefan Monnier
2016-03-22 16:28                                                 ` Vitalie Spinu
2016-03-22 16:44                                                   ` Stefan Monnier
2016-03-22 19:36                                                     ` Vitalie Spinu
2016-03-23  2:22                                                       ` Stefan Monnier
2016-03-23 11:41                                                         ` Vitalie Spinu
2016-03-23 12:34                                                           ` Stefan Monnier
2016-03-23 12:41                                                             ` Vitalie Spinu
2016-03-29 21:43                                                               ` Vitalie Spinu
2016-04-22 14:34                                                                 ` Dmitry Gutov
2016-04-24  7:22                                                                   ` Vitalie Spinu
2016-04-24  7:28                                                                     ` Achim Gratz
2016-04-24 11:33                                                                       ` Vitalie Spinu
2016-04-24 13:20                                                                         ` Andreas Schwab
2016-04-24 16:11                                                                           ` Vitalie Spinu
2016-04-24 16:19                                                                             ` Andreas Schwab
2016-04-24 16:41                                                                               ` Vitalie Spinu
2016-04-24 16:48                                                                                 ` Andreas Schwab
2016-04-24 18:01                                                                                   ` Vitalie Spinu
2016-04-24 19:05                                                                                     ` Andreas Schwab
2016-04-28 13:29                                                 ` Vitalie Spinu
2016-04-30 14:06                                                   ` Stefan Monnier
2016-03-22 20:08                                               ` Richard Stallman
2016-03-22 22:45                                                 ` Vitalie Spinu
2016-03-21 11:47                         ` Syntax tables for multiple modes [was: bug#22983: syntax-ppss returns wrong result.] Dmitry Gutov
2016-03-21 12:40                           ` Vitalie Spinu
2016-03-21 13:07                             ` Dmitry Gutov
2016-03-21 14:20                               ` Vitalie Spinu
2016-03-21 14:29                                 ` Dmitry Gutov
2016-03-21 14:42                                   ` Vitalie Spinu
2016-03-21 14:56                                     ` Dmitry Gutov
2016-03-21 16:52                                       ` Vitalie Spinu
2016-03-21 21:30                                         ` Dmitry Gutov
2016-04-03 23:34                                           ` John Wiegley
2016-03-21 14:02                             ` Stefan Monnier
2016-03-21 14:31                               ` Vitalie Spinu
2016-03-21 15:06                                 ` Stefan Monnier
2016-03-21 17:15                                   ` Andreas Röhler
2016-03-13 17:32     ` bug#22983: syntax-ppss returns wrong result Stefan Monnier
2016-03-13 18:52 ` Andreas Röhler
2016-03-13 18:56   ` Dmitry Gutov
2016-03-18  0:49 ` Dmitry Gutov
2016-03-19 12:27   ` Alan Mackenzie
2016-03-19 18:47     ` Dmitry Gutov
2016-03-27  0:51       ` John Wiegley
2016-03-27  1:14         ` Dmitry Gutov
2016-04-03 22:58           ` John Wiegley
2016-04-03 23:15             ` Dmitry Gutov
2017-09-02 13:12               ` Eli Zaretskii
2017-09-02 17:40                 ` Alan Mackenzie
2017-09-02 17:53                   ` Eli Zaretskii
2017-09-03 20:44                   ` John Wiegley
2017-09-04 23:34                   ` Dmitry Gutov
2017-09-05  6:57                     ` Andreas Röhler
2017-09-05 12:28                     ` John Wiegley
2017-09-07 20:45                       ` Alan Mackenzie
2017-09-08 16:04                         ` Andreas Röhler
2017-09-10 18:26                           ` Alan Mackenzie
2017-09-09  9:44                         ` Dmitry Gutov
2017-09-09 10:20                           ` Alan Mackenzie
2017-09-09 12:18                             ` Dmitry Gutov
2017-09-10 11:42                               ` Alan Mackenzie
2017-09-10 11:36                           ` bug#22983: [ Patch ] " Alan Mackenzie
2017-09-10 22:53                             ` Stefan Monnier
2017-09-10 23:36                               ` Dmitry Gutov
2017-09-11 11:10                                 ` Stefan Monnier
2017-09-12  0:11                                   ` Dmitry Gutov
2017-09-12 22:12                                     ` Richard Stallman
2017-09-11 19:42                               ` Alan Mackenzie
2017-09-11 20:20                                 ` Stefan Monnier
2017-09-11  0:11                             ` Dmitry Gutov
2017-09-11 20:12                               ` Alan Mackenzie
2017-09-12  0:24                                 ` Dmitry Gutov
2017-09-17 10:29                                   ` Alan Mackenzie
2017-09-17 23:43                                     ` Dmitry Gutov
2017-09-18 19:08                                       ` Alan Mackenzie
2017-09-19  0:02                                         ` Dmitry Gutov
2017-09-19 20:47                                           ` Alan Mackenzie
2017-09-22 14:09                                             ` Dmitry Gutov
2017-09-24 11:26                                               ` Alan Mackenzie
2017-09-25 23:53                                                 ` Dmitry Gutov
2017-10-01 16:36                                                   ` Alan Mackenzie
2017-10-04 20:07                                                 ` Johan Bockgård
2017-09-17 11:12                             ` Philipp Stephani
2017-09-19 20:50                               ` Alan Mackenzie
2017-09-07 17:56                     ` Alan Mackenzie
2017-09-07 20:36                       ` Dmitry Gutov
2016-03-19 23:16     ` Vitalie Spinu
2016-03-19 23:00   ` Vitalie Spinu
2016-03-19 23:20     ` Dmitry Gutov
     [not found] ` <mailman.7307.1457709188.843.bug-gnu-emacs@gnu.org>
2017-10-01 16:31   ` Alan Mackenzie

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