From: Mark Wielaard <mark@klomp.org>
To: Siddhesh Poyarekar <siddhesh@gotplt.org>,
Alejandro Colomar <alx.manpages@gmail.com>, GCC <gcc@gcc.gnu.org>
Cc: "Iker Pedrosa" <ipedrosa@redhat.com>,
"David Malcolm" <dmalcolm@redhat.com>,
"Florian Weimer" <fweimer@redhat.com>,
"Sam James" <sam@gentoo.org>, "Paul Eggert" <eggert@cs.ucla.edu>,
"Michael Kerrisk" <mtk.manpages@gmail.com>,
"Martin Uecker" <uecker@tugraz.at>,
"Jₑₙₛ Gustedt" <jens.gustedt@inria.fr>,
"Yann Droneaud" <ydroneaud@opteya.com>
Subject: Re: Missed warning (-Wuse-after-free)
Date: Fri, 17 Feb 2023 15:01:58 +0100 [thread overview]
Message-ID: <4bac5d2f550243e2782e4477aeb29fdb1c331a0a.camel@klomp.org> (raw)
In-Reply-To: <e8a6894b-f493-a147-9c9a-f83353896b84@gotplt.org>
On Fri, 2023-02-17 at 08:38 -0500, Siddhesh Poyarekar wrote:
> On 2023-02-17 06:22, Alejandro Colomar wrote:
> > Hi Siddhesh,
> >
> > On 2/17/23 04:48, Siddhesh Poyarekar wrote:
> > > On 2023-02-16 10:15, David Malcolm via Gcc wrote:
> > > > I'm not convinced that it's useful to the end-user to warn about the
> > > > "use of q itself" case.
> > >
> > > FWIW, -Wuse-after-free=3 already should do this:
> >
> > Thanks! It works. I would have expected such a warning to be included
> > in -Wextra. Does it have any false positives (or maybe too many false
> > negatives?) that make it unsuitable for -Wextra?
>
> I don't know why it isn't enabled in -Wextra, it seems like the right
> thing to do.
Interesting warning flag I didn't know about. It seems to have found an
issue in some code trying to free a circular single linked list:
https://inbox.sourceware.org/elfutils-devel/20230217140027.125332-1-mark@klomp.org/
The reason people might not know about it, is that the documentation is
somewhat unclear. -Wall says it already includes -Wuse-after-free=3:
https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wall
But the -Wuse-after-free option itself says -Wall only enables -Wuse-
after-free=2:
https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Dialect-Options.html#index-Wuse-after-free
Also note that it is listed under "Options Controlling C++ Dialect" so
it wasn't immediately clear to me that it also works for C.
Cheers,
Mark
next prev parent reply other threads:[~2023-02-17 14:02 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
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 [this message]
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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