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From: Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: 65491@debbugs.gnu.org,
	"Mattias Engdegård" <mattias.engdegard@gmail.com>,
	"Eli Zaretskii" <eliz@gnu.org>
Subject: bug#65491: [PATCH] Improve performance allocating vectors
Date: Mon, 18 Sep 2023 10:19:09 +0800	[thread overview]
Message-ID: <87jzsoxlya.fsf@yahoo.com> (raw)
In-Reply-To: <jwvy1h4rb71.fsf-monnier+emacs@gnu.org> (Stefan Monnier's message of "Sun, 17 Sep 2023 13:02:15 -0400")

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Even converting them back to their original pointer (which is what we do
> with tag/untag pairs) is documented to be well-defined if you compile
> using GCC.

Only if the consequent pointer designates the same object as the initial
pointer (of which I see no scrutable definition within GCC's
documentation.)  But in practice, this doesn't matter, or so I thought.

> In contrast the pointer arithmetic on NULL pointers appears to be
> something which compilers have started to (ab)use as an assumption for
> their optimizations.  Hence the need to update our code.

Hmm?  Where in this thread was that fact established?

Thanks.





  reply	other threads:[~2023-09-18  2:19 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-24  9:59 bug#65491: [PATCH] Improve performance allocating vectors Ihor Radchenko
2023-08-26  7:14 ` Eli Zaretskii
2023-08-26  7:27   ` Ihor Radchenko
2023-08-26  7:31     ` Eli Zaretskii
2023-08-26  7:51       ` Ihor Radchenko
2023-08-26  8:07         ` Ihor Radchenko
2023-08-26  9:01         ` Eli Zaretskii
2023-08-26  7:47     ` Ihor Radchenko
2023-08-26 12:01 ` Mattias Engdegård
2023-08-26 14:54   ` Ihor Radchenko
2023-08-26 14:55   ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-08-27  9:54     ` Mattias Engdegård
2023-09-16 14:58     ` Mattias Engdegård
2023-09-16 16:12       ` Eli Zaretskii
2023-09-16 16:17         ` Eli Zaretskii
2023-09-16 16:32           ` Mattias Engdegård
2023-09-16 16:54             ` Eli Zaretskii
2023-09-16 17:03               ` Mattias Engdegård
2023-09-16 17:11                 ` Eli Zaretskii
2023-09-17  3:02                 ` Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-17 17:02                   ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-18  2:19                     ` Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors [this message]
2023-09-18  2:27                       ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-18  3:08                         ` Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-18  4:10                           ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-16 16:54             ` Mattias Engdegård
2023-09-16 17:09               ` Eli Zaretskii
2023-09-16 17:22                 ` Mattias Engdegård
2023-09-16 18:19                   ` Eli Zaretskii
2023-09-16 19:04                     ` Mattias Engdegård
2023-09-16 19:46                 ` Paul Eggert
2023-09-17  5:18                   ` Eli Zaretskii
2023-09-17 15:22                     ` Paul Eggert
2023-09-17 16:15                       ` Eli Zaretskii
2023-09-17 16:37                         ` Paul Eggert
2023-09-17 16:44                           ` Eli Zaretskii
2023-09-18 16:10                             ` Mattias Engdegård
2023-09-18 17:13                               ` Eli Zaretskii
2023-09-19 13:28                               ` Mattias Engdegård
2023-09-19 14:04                                 ` Eli Zaretskii
2023-09-19 14:05                                   ` Mattias Engdegård
2023-09-25 16:06       ` Mattias Engdegård
2023-08-27 16:21 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-08-28 10:14   ` Ihor Radchenko
2023-08-28 16:32     ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-08-28 12:47   ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors

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