From: Eric Blake <eblake@redhat.com>
To: Alejandro Colomar <alx.manpages@gmail.com>
Cc: linux-man@vger.kernel.org, "Alejandro Colomar" <alx@kernel.org>,
GCC <gcc@gcc.gnu.org>, glibc <libc-alpha@sourceware.org>,
"Bastien Roucariès" <rouca@debian.org>,
"Stefan Puiu" <stefan.puiu@gmail.com>,
"Igor Sysoev" <igor@sysoev.ru>, "Rich Felker" <dalias@libc.org>,
"Andrew Clayton" <a.clayton@nginx.com>,
"Richard Biener" <richard.guenther@gmail.com>,
"Zack Weinberg" <zack@owlfolio.org>,
"Florian Weimer" <fweimer@redhat.com>,
"Joseph Myers" <joseph@codesourcery.com>,
"Jakub Jelinek" <jakub@redhat.com>
Subject: Re: [PATCH] sockaddr.3type: BUGS: Document that libc should be fixed using a union
Date: Mon, 6 Feb 2023 12:45:30 -0600 [thread overview]
Message-ID: <20230206184530.zn5kq7x6xmcfxhqm@redhat.com> (raw)
In-Reply-To: <20230205152835.17413-1-alx@kernel.org>
On Sun, Feb 05, 2023 at 04:28:36PM +0100, Alejandro Colomar wrote:
Regardless of the merits of the patch, let's not introduce typos:
> +++ b/man3type/sockaddr.3type
> @@ -120,6 +120,26 @@ .SH NOTES
> .I <netinet/in.h>
> and
> .IR <sys/un.h> .
> +.SH BUGS
> +.I sockaddr_storage
> +was designed back when strict aliasing wasn't a problem.
> +Back then,
> +one would define a variable of that type,
> +and then access it as any of the other
> +.IR sockaddr_ *
> +types,
> +depending on the value of the first member.
> +This is Undefined Behavior.
> +However, there is no way to use these APIs without invoking Unedfined Behavior,
Undefined
> +either in the user program or in libc,
> +so it is still recommended to use this method.
> +The only correct way to use different types in an API is through a union.
> +However,
> +that union must be implemented in the library,
> +since the type must be shared between the library and user code,
> +so libc should be fixed by implementing
> +.I sockaddr_storage
> +as a union.
> .SH SEE ALSO
> .BR accept (2),
> .BR bind (2),
Also, while I could raise the issue with the Austin Group on your
behalf to get the POSIX wording improved, I think it would work better
if you initiate a bug report rather than having me do it:
https://www.austingroupbugs.net/main_page.php
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
next prev parent reply other threads:[~2023-02-06 18:45 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-05 15:28 Alejandro Colomar
2023-02-05 15:31 ` Alejandro Colomar
2023-02-06 6:02 ` Xi Ruoyao
2023-02-06 11:20 ` Rich Felker
2023-02-06 11:55 ` Alejandro Colomar
2023-02-06 13:38 ` Rich Felker
2023-02-06 14:11 ` Alejandro Colomar
2023-02-06 17:21 ` Zack Weinberg
2023-02-06 17:48 ` Rich Felker
2023-02-05 23:43 ` Rich Felker
2023-02-05 23:59 ` Alejandro Colomar
2023-02-06 0:15 ` Rich Felker
2023-02-06 18:45 ` Eric Blake [this message]
2023-02-07 1:21 ` Alejandro Colomar
2023-03-18 7:54 ` roucaries bastien
2023-03-20 10:49 ` Alejandro Colomar
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