GNU bug report logs - #69706
30.0.50; sort.c, unnecessary GC marking

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From: Mattias Engdegård <mattias.engdegard <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: Gerd Möllmann <gerd.moellmann <at> gmail.com>, Stefan Monnier <monnier <at> iro.umontreal.ca>, 69706 <at> debbugs.gnu.org
Subject: bug#69706: 30.0.50; sort.c, unnecessary GC marking
Date: Sun, 10 Mar 2024 12:16:42 +0100

>> sort.c uses record_unwind_protect_mark to let GC mark some objects in
>> its merge_state structure, while GC marks the specpdl stack.
>> 
>> This is
>> 
>> - unnecessary because all the objects that are currrently extra
>>  protected by merge_markmem, are already seen by the GC, because these
>>  are the objects being sorted, which are protected in the usual way
>>  (marking the control stack, ...)

Thank you Gerd, but I don't think we can guarantee that those objects are present anywhere else -- the original vector is being mutated by the algorithm, after all.

In addition, I have Grand Plans (well, some kind of plans) for an improvement to the sorting code that will likely require record_unwind_protect_mark or an equivalent facility. A new bug will be opened about that.

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