Re: AF_LOCAL vs AF_UNIX

[Bruno Haible]

Hi Nikos,

Nikos Mavrogiannopoulos wrote:
>  I've noticed that some systems define AF_LOCAL in sys/socket.h while
> others AF_UNIX and most define both. Could gnulib provide both
> definitions (e.g. by this patch) to simplify their usage on various
> platforms?

Gnulib is meant to allow people to program according to POSIX (and, to a
lesser extent, GNU) APIs. Since POSIX [1] specifies the existence of AF_UNIX
but not of AF_LOCAL, there is no point for Gnulib to support AF_LOCAL.

Which are the platforms which provide AF_LOCAL but not AF_UNIX? I can't see
any.

I see some platforms which provide AF_UNIX but not AF_LOCAL (Minix, AIX,
HP-UX 10, OSF/1, mingw, MSVC 9, Plan9). But since Gnulib's objective is
to provide AF_UNIX, not AF_LOCAL, this list of platforms is not relevant.

Also, which kind of program can use AF_UNIX without using <sys/un.h>?
According to gnulib/doc/posix-headers/sys_un.texi, <sys/un.h> is missing
on native Windows, and Gnulib provides no replacement for it. The reason
is that Gnulib cannot just invent a new kind of socket, and things that
are done with AF_UNIX sockets on Unix are often better done with pipes
on Windows.

Bruno

[1] http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_socket.h.html