GNU bug report logs - #11216
23.4; parenthesis matching breaks on certain complex expressions

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Nathan Trapuzzano <nbtrap <at> nbtrap.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 23.4; parenthesis matching breaks on certain complex expressions
Date: Tue, 10 Apr 2012 20:18:47 -0400

[Message part 1 (text/plain, inline)]

Here's a complex regular expression that breaks parenthesis matching
(and yes, that's a real regular expression generated from a real perl
program).


M[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*H[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*\=[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*N[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*I[\=\/\\]?[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*N(?![\x21\x27\x2a\x2d\x2f\x3d\x41-\x5a\x5c\x61-\x7a\x7c]) (?<!S\d)(?<!\-\ [@"]\d\ [\x80-\xff])(?<!\-[\x80-\xff][\x80-\xff])(?<!\-[\x80-\xff])(?<![\x27-\x29\x2f\x3d\x41-\x5a\x7c]\*)(?<![\x27-\x29\x2f\x3d\x41-\x5a\x7c])(?:A\)[\/\\]|\*\)[\/\\]A[\=\/\\]?)[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*E[\=\/\\]?[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*I[\=\/\\]?[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*D[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*E[\=\/\\]?(?![\x21\x27\x2a\x2d\x2f\x3d\x41-\x5a\x5c\x61-\x7a\x7c]) (?<!S\d)(?<!\-\ [@"]\d\ [\x80-\xff])(?<!\-[\x80-\xff][\x80-\xff])(?<!\-[\x80-\xff])(?<![\x27-\x29\x2f\x3d\x41-\x5a\x7c]\*)(?<![\x27-\x29\x2f\x3d\x41-\x5a\x7c])Q[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*E[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*A[?+]?(?:-(?:[\x01-\x7f]*[\x00\x80-\xff]+))?[\x02-\x19\x22-\x27\x28-\x2e\x30-\x3c\x3e-\x40\x5b\x5d-\x7b\x7d-\xff]*[\/\\]

Matching gets messed up with the open parenthesis immediately following
the first (?<!S\d). I suspect this is due to the opening double-quote
about 10 characters later.

I noticed that the behavior of show-paren-mode changes depending on the
major mode. For example, the behavior described above happens in
fundamental mode, whereas when I switch to text mode, quotation marks
are ignored. However, switching to text mode also causes paren-matching
to ignore back-slashes and thus escaped parentheses/brackets. I think
the best fix would be to enable customization of show-paren-mode so
that the user can specify which characters should be ignored when
matching parentheses.

I've also attached a file containing the regexp in question in case the long line gets broken up over mail transmission.

[regexp.txt (text/plain, attachment)]

Message #8 received at 11216 <at> debbugs.gnu.org (full text, mbox):

From: Andreas Schwab <schwab <at> linux-m68k.org>
To: Nathan Trapuzzano <nbtrap <at> nbtrap.com>
Cc: 11216 <at> debbugs.gnu.org
Subject: Re: bug#11216: 23.4;
	parenthesis matching breaks on certain complex expressions
Date: Wed, 11 Apr 2012 09:09:21 +0200

Nathan Trapuzzano <nbtrap <at> nbtrap.com> writes:

> Matching gets messed up with the open parenthesis immediately following
> the first (?<!S\d). I suspect this is due to the opening double-quote
> about 10 characters later.

No, it's because < has open paren syntax, but there is no matching
close paren.  This is not a bug.  You need to use a suitable syntax
table that doesn't make < a paren syntax.

Andreas.

-- 
Andreas Schwab, schwab <at> linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Message #11 received at 11216 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Nathan Trapuzzano <nbtrap <at> nbtrap.com>
Cc: 11216 <at> debbugs.gnu.org
Subject: Re: bug#11216: 23.4;
	parenthesis matching breaks on certain complex expressions
Date: Wed, 11 Apr 2012 22:08:39 -0400

> Here's a complex regular expression that breaks parenthesis matching
> (and yes, that's a real regular expression generated from a real perl
> program).
[...]
> I think the best fix would be to enable customization of
> show-paren-mode so that the user can specify which characters should
> be ignored when matching parentheses.

show-paren-mode is customized by the major-mode, so all you have to do
is use the right major mode.  E.g. perl-mode.


        Stefan

Message #14 received at 11216 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefan <at> marxist.se>
To: Andreas Schwab <schwab <at> linux-m68k.org>
Cc: Nathan Trapuzzano <nbtrap <at> nbtrap.com>, 11216 <at> debbugs.gnu.org
Subject: Re: bug#11216: 23.4; parenthesis matching breaks on certain complex
 expressions
Date: Fri, 01 Nov 2019 21:11:27 +0100

tags 11216 + notabug
close 11216
thanks

Andreas Schwab <schwab <at> linux-m68k.org> writes:

> Nathan Trapuzzano <nbtrap <at> nbtrap.com> writes:
>
>> Matching gets messed up with the open parenthesis immediately following
>> the first (?<!S\d). I suspect this is due to the opening double-quote
>> about 10 characters later.
>
> No, it's because < has open paren syntax, but there is no matching
> close paren.  This is not a bug.  You need to use a suitable syntax
> table that doesn't make < a paren syntax.

With the above explanaition, I'm closing this as notabug.

Please reopen if this is incorrect.

Best regards,
Stefan Kangas

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