From: Andreas Schwab <schwab@linux-m68k.org>
To: Alejandro Colomar via Gcc <gcc@gcc.gnu.org>
Cc: "Martin Uecker" <uecker@tugraz.at>,
"Jonathan Wakely" <jwakely.gcc@gmail.com>,
"Alejandro Colomar" <alx.manpages@gmail.com>,
"Iker Pedrosa" <ipedrosa@redhat.com>,
"Florian Weimer" <fweimer@redhat.com>,
"Paul Eggert" <eggert@cs.ucla.edu>,
"Michael Kerrisk" <mtk.manpages@gmail.com>,
"Jₑₙₛ Gustedt" <jens.gustedt@inria.fr>,
"David Malcolm" <dmalcolm@redhat.com>,
"Sam James" <sam@gentoo.org>,
"Yann Droneaud" <ydroneaud@opteya.com>
Subject: Re: Missed warning (-Wuse-after-free)
Date: Fri, 17 Feb 2023 14:34:25 +0100 [thread overview]
Message-ID: <87mt5c5sbi.fsf@igel.home> (raw)
In-Reply-To: <0049730a-e28c-0e0f-8d92-695395f1ec21@gmail.com> (Alejandro Colomar via Gcc's message of "Fri, 17 Feb 2023 12:35:06 +0100")
On Feb 17 2023, Alejandro Colomar via Gcc wrote:
> C2x (N3054 is the latest I know):
>
> If a pointer value is used in an evaluation after
> the object the pointer points to (or just past)
> reaches the end of its lifetime,
> the behavior is undefined.
> <https://www.open-std.org/JTC1/SC22/WG14/www/docs/n3054.pdf#subsection.6.2.4>
>
>
> This new wording doesn't even allow one to use memcmp(3);
> just reading the pointer value, however you do it, is UB.
But memcmp does not read the value, it reads the object representation,
and reading the representation is never UB.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
next prev parent reply other threads:[~2023-02-17 13:34 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-16 14:35 Alejandro Colomar
2023-02-16 15:15 ` David Malcolm
2023-02-17 1:04 ` Alejandro Colomar
2023-02-17 1:05 ` Alejandro Colomar
2023-02-17 1:56 ` Sam James
2023-02-17 8:12 ` Martin Uecker
2023-02-17 11:35 ` Alejandro Colomar
2023-02-17 13:34 ` Andreas Schwab [this message]
2023-02-17 13:48 ` Martin Uecker
2023-02-23 19:23 ` Alex Colomar
2023-02-23 19:57 ` Martin Uecker
2023-02-24 0:02 ` Alex Colomar
2023-02-24 1:21 ` Serge E. Hallyn
2023-02-24 1:42 ` Alex Colomar
2023-02-24 3:01 ` Peter Lafreniere
2023-02-24 8:52 ` Martin Uecker
2023-02-24 8:43 ` Martin Uecker
2023-02-24 16:10 ` Serge E. Hallyn
2023-02-24 8:36 ` Martin Uecker
2023-02-24 16:01 ` Serge E. Hallyn
2023-02-24 16:37 ` Martin Uecker
2023-02-17 3:48 ` Siddhesh Poyarekar
2023-02-17 11:22 ` Alejandro Colomar
2023-02-17 13:38 ` Siddhesh Poyarekar
2023-02-17 14:01 ` Mark Wielaard
2023-02-17 14:06 ` Siddhesh Poyarekar
2023-02-17 21:20 ` [PATCH] Make -Wuse-after-free=3 the default one in -Wall Alejandro Colomar
2023-02-17 21:39 ` Siddhesh Poyarekar
2023-02-17 21:41 ` Siddhesh Poyarekar
2023-02-17 22:58 ` Alejandro Colomar
2023-02-17 23:03 ` Siddhesh Poyarekar
2023-02-17 11:24 ` Missed warning (-Wuse-after-free) Jonathan Wakely
2023-02-17 11:43 ` Alejandro Colomar
2023-02-17 12:04 ` Jonathan Wakely
2023-02-17 12:53 ` Siddhesh Poyarekar
2023-02-17 14:10 ` Jonathan Wakely
2023-02-17 13:44 ` David Malcolm
2023-02-17 14:01 ` Siddhesh Poyarekar
2023-02-17 8:49 ` Yann Droneaud
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