GNU bug report logs - #54532
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Package: emacs;

Reported by: Andrew Cohen <acohen <at> ust.hk>

Date: Wed, 23 Mar 2022 00:00:02 UTC

Severity: wishlist

Tags: patch

Fixed in version 29.1

Done: Stefan Kangas <stefan <at> marxist.se>

Bug is archived. No further changes may be made.

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Message #17 received at 54532 <at> debbugs.gnu.org (full text, mbox):

From: Mattias Engdegård <mattiase <at> acm.org>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: Andrew Cohen <acohen <at> ust.hk>, 54532 <at> debbugs.gnu.org
Subject: bug#54532: [PATCH] sorting
Date: Wed, 23 Mar 2022 21:24:16 +0100

> Can you tell more why this was needed? Emacs has conservative stack marking, so any Lisp object that is referred by some stack-based variable should be protected from GC. Why isn't that enough in this case?

Because Lisp values are temporarily moved out to a heap allocated buffer which isn't traversed by the stack scanner. `record_unwind_protect_ptr_mark` can be seen as a generalisation of `record_unwind_protect_ptr` (because that's what it is).

> Is this really eassume, or is eassert better here?

No, eassume is appropriate here. It provides more optimisation opportunities.
In fact, most uses of eassert are better or just as good as eassume as long as there are no function calls or tricky memory dereferences.
This bug report was last modified 3 years and 43 days ago.

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