From: Martin Uecker <uecker@tugraz.at>
To: Peter Lafreniere <peter@n8pjl.ca>, Alex Colomar <alx.manpages@gmail.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>, GCC <gcc@gcc.gnu.org>,
"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>,
"Jonathan Wakely" <jwakely.gcc@gmail.com>
Subject: Re: Missed warning (-Wuse-after-free)
Date: Fri, 24 Feb 2023 09:52:11 +0100 [thread overview]
Message-ID: <045dec6a3f28b237863deedf8ae0b244bd269145.camel@tugraz.at> (raw)
In-Reply-To: <M3fv3--Z75IMxKlK2UOrUI-jnAx6O2YDmO_xC7r_37dMReb-BanrJSbZaJgupp70c0Op1gFzHFB8e3SeVEStOugJwHEIMLWca4nXNLVpFaQ=@n8pjl.ca>
Am Freitag, dem 24.02.2023 um 03:01 +0000 schrieb Peter Lafreniere:
...
>
> > Maybe it could do an exception for printing, that is, reading a pointer
> > is not a problem in itself, a long as you don't compare it, but I'm not
> > such an expert about this.
>
> One last thought: with the above strict interpretation of the c standard,
> it would become nigh on impossible to implement the malloc(3) family of
> functions in c themselves. I vote for the "shared storage" interpretation
> of the c11 standard that is actually implemented rather than this abstract
> liveness oriented interpretation.
This is a bit of a misunderstanding about what "undefined behavior" means
in ISO C. It simply means that ISO C does not specify the behavior. This
does not mean it is illegal to do something which has undefined behavior.
Instead, it means you can not rely on the ISO C standard for portable
behavior. So if you implement "malloc" in C itself you will probably
rely on "undefined behavior", but this is perfectly fine. The C standard
specifies behavior of "malloc", but does not care how it is implemented.
Martin
next prev parent reply other threads:[~2023-02-24 8:52 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
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 [this message]
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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