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bug#23704: 25.1.50; Emacs crash in syntax.c
From: |
Andreas Schwab |
Subject: |
bug#23704: 25.1.50; Emacs crash in syntax.c |
Date: |
Mon, 06 Jun 2016 17:03:28 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) |
Eli Zaretskii <eliz@gnu.org> writes:
>> From: Andreas Schwab <schwab@suse.de>
>> Date: Mon, 06 Jun 2016 09:36:07 +0200
>> Cc: 23704@debbugs.gnu.org
>>
>> > 2233 if (! fastmap[SYNTAX (*p)])
>>
>> I think I have seen a similar crash with the emacs-25 branch as well,
>> but only once, and I couldn't reproduce it so far.
>
> If my reading of the code is correct, we have pointers to buffer text
> and the gap lying around, while invoking code that can GC (which
> compacts buffers). For example, the sequence of calls
>
> SETUP_SYNTAX_TABLE
> -> SETUP_BUFFER_SYNTAX_TABLE
> -> update_syntax_table_forward
> -> parse_sexp_propertize
>
> could call Lisp, and that happens after we already computed the values
> of p, endp, and stop. Likewise the call to UPDATE_SYNTAX_TABLE_FORWARD
> we make inside the loop.
>
> If GC decides to compact the gap, it could well make a previously
> valid pointer invalid.
>
> Could that be the reason?
Yes, that looks very likely.
Andreas.
--
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."
- bug#23704: 25.1.50; Emacs crash in syntax.c, Vincent Belaïche, 2016/06/06
- bug#23704: 25.1.50; Emacs crash in syntax.c, Andreas Schwab, 2016/06/06
- bug#23704: 25.1.50; Emacs crash in syntax.c, Eli Zaretskii, 2016/06/06
- bug#23704: 25.1.50; Emacs crash in syntax.c, Paul Eggert, 2016/06/06
- bug#23704: 25.1.50; Emacs crash in syntax.c, Eli Zaretskii, 2016/06/06
- bug#23704: 25.1.50; Emacs crash in syntax.c, Paul Eggert, 2016/06/06
- bug#23704: 25.1.50; Emacs crash in syntax.c, Eli Zaretskii, 2016/06/06
- bug#23704: 25.1.50; Emacs crash in syntax.c, Paul Eggert, 2016/06/07
- bug#23704: 25.1.50; Emacs crash in syntax.c, Eli Zaretskii, 2016/06/07
- bug#23704: 25.1.50; Emacs crash in syntax.c, Paul Eggert, 2016/06/07