From: Rich Felker <dalias@libc.org>
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>,
"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>,
"Eric Blake" <eblake@redhat.com>
Subject: Re: [PATCH] sockaddr.3type: BUGS: Document that libc should be fixed using a union
Date: Sun, 5 Feb 2023 18:43:59 -0500 [thread overview]
Message-ID: <20230205234359.GF3298@brightrain.aerifal.cx> (raw)
In-Reply-To: <20230205152835.17413-1-alx@kernel.org>
On Sun, Feb 05, 2023 at 04:28:36PM +0100, Alejandro Colomar wrote:
> As discussed before, and Bastien and I seem to agree, ideally we should
> define the following types:
>
> struct sockaddr_storage {
> union {
> struct {
> sa_family_t ss_family;
> };
> struct sockaddr_in sin;
> struct sockaddr_in6 sin6;
> struct sockaddr_un sun;
> // ...
> };
> };
AFAIK this is not permitted because of namespace. sys/socket.h is not
permitted to expose sockaddr_{in,in6,un}. And if you defined
differently-tagged structures with the same contents, it would not do
any good; accessing the members with the wrong-tagged struct type
would still be UB.
Really, there is no action needed here. Nothing is wrong on libc's
side. The problem is just that the type is *not useful for anything*
and should not be used except in the context of sizeof, which is
purely a documentation issue.
> struct [[deprecated]] sockaddr {
> sa_family_t sa_family;
> };
>
> union [[gnu::transparent_union]] sockaddr_ptr {
> struct sockaddr_storage *ss;
> struct sockaddr *sa;
> };
>
> And then we could define APIs like:
>
> int bind(int sockfd, const union sockaddr_ptr *addr, socklen_t len);
You cannot just change APIs because you wish they were different.
Ideally bind, etc. would just take void *, which is what the struct
sockaddr * is being used as. But they don't, so callers have to cast.
It's ugly but it's really not a big deal. Much less of a big deal than
breaking the interface because you think it would look prettier if it
had been done differently.
Rich
next prev parent reply other threads:[~2023-02-05 23:44 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 [this message]
2023-02-05 23:59 ` Alejandro Colomar
2023-02-06 0:15 ` Rich Felker
2023-02-06 18:45 ` Eric Blake
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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