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bug#10164: 24.0.91; Instant crash enabling linum-mode
From: |
Dan Nicolaescu |
Subject: |
bug#10164: 24.0.91; Instant crash enabling linum-mode |
Date: |
Wed, 30 Nov 2011 10:51:01 -0500 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.3 (gnu/linux) |
Eli Zaretskii <eliz@gnu.org> writes:
>> From: Dan Nicolaescu <dann@gnu.org>
>> Cc: Tim Crews <tim.crews@code-affinity.com>, 10164@debbugs.gnu.org
>> Date: Wed, 30 Nov 2011 07:52:40 -0500
>>
>> Eli Zaretskii <eliz@gnu.org> writes:
>>
>> >> Date: Tue, 29 Nov 2011 19:05:20 -0700
>> >> From: Tim Crews <tim.crews@code-affinity.com>
>> >>
>> >> Start Emacs with runemacs -Q --no-init-file
>> >> C-x C-f foo.txt
>> >> M-x linum-mode
>> >> (Emacs doesn't crash yet)
>> >> Type anything. Emacs instantly crashes.
>> >
>> > Arrgh! This is GCC 4.6.x "as-is" code reordering in action. Emacs
>> > crashes here:
>> >
>> > xassert (!row->enabled_p
>> > || row->mode_line_p
>> > || verify_row_hash (row));
>> >
>> > Evidently, it calls verify_row_hash before it tests row->mode_line_p.
>>
>> Are you sure?
>
> How else can I explain this display from GDB:
Compiler bug?
> (gdb) prow
> y=0 x=0 pwid=673 a+d=12+4=16 phys=12+4=16 vis=16
> used=(LMargin=0,Text=84,RMargin=0) Hash=263825844
> start=0 end=0 ENA MODEL
>
> ? MODEL says that this row has its mode_line_p flag set.
>
> Just to be sure, I ran the recipe again under GDB, setting a
> breakpoint inside verify_row_hash thusly:
>
> (gdb) break verify_row_hash if row->mode_line_p != 0
>
> and sure enough, it breaks as soon as I turn on linum-mode, with ROW
> that shows the glyphs in the mode line.
>
>> Without interprocedural analysis the compiler cannot know
>> that `verify_row_hash' does not alter row->enabled_p, so it cannot
>> change the evaluation order.
>
> I don't know. Maybe GCC does perform such an analysis. Or maybe it
It can't by default, `row_hash' is in a different file, so it's not
available when compiling dispnew.c.
> decides that the result of this comparison in verify_row_hash:
>
> row->hash == row_hash (row)
>
> will not change even if row_hash does modify its argument ROW. Or
> maybe it's a bug in GCC.
bug#10164: 24.0.91; Instant crash enabling linum-mode, Eli Zaretskii, 2011/11/30
- bug#10164: 24.0.91; Instant crash enabling linum-mode, Juanma Barranquero, 2011/11/30
- bug#10164: 24.0.91; Instant crash enabling linum-mode, Eli Zaretskii, 2011/11/30
- Message not available
- Message not available
- Message not available
- bug#10164: 24.0.91; Instant crash enabling linum-mode, Eli Zaretskii, 2011/11/30
- bug#10164: 24.0.91; Instant crash enabling linum-mode, Chong Yidong, 2011/11/30
- bug#10164: 24.0.91; Instant crash enabling linum-mode, Chong Yidong, 2011/11/30
- bug#10164: 24.0.91; Instant crash enabling linum-mode, Juanma Barranquero, 2011/11/30
- bug#10164: 24.0.91; Instant crash enabling linum-mode, Chong Yidong, 2011/11/30