GNU bug report logs - #69709
`sort` interface improvement and universal ordering predicate

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From: Mattias Engdegård <mattias.engdegard <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 69709 <at> debbugs.gnu.org, Aris Spathis <agspathis <at> gmail.com>
Subject: bug#69709: `sort` interface improvement and universal ordering predicate
Date: Sun, 14 Apr 2024 18:33:32 +0200

14 apr. 2024 kl. 18.26 skrev Eli Zaretskii <eliz <at> gnu.org>:

>> Thank you for your excellent work on `sort` and related functionality!

Apparently not excellent enough!

>> Unfortunately, the new `sort` implementation occasionally crashes with a
>> segfault. The following code reproduces that in current master:
>> 
>> (dotimes (i 500)
>>  (sort (make-list 128 42)
>>        :key (lambda (n) (make-list i n))))
>> 
>> It happens for inputs of length >= `MERGESTATE_TEMP_SIZE / 2` (= 128
>> currently) along with a non-NIL `:key` function. In such cases, a
>> `Lisp_Object` array is explicitly heap-allocated to store the keys, which is
>> never marked against GC. This would not be a problem if not for the fact that
>> the `:key` function call may trigger GC.

Oh dear, what a silly mistake. Many thanks for spotting this and providing the patch, which I applied with a few minor adjustments (and a regression test).

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