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Re: socklen_t data type

From: Bruno Haible
Subject: Re: socklen_t data type
Date: Tue, 30 Jun 2020 03:07:39 +0200
User-agent: KMail/5.1.3 (Linux/4.4.0-179-generic; KDE/5.18.0; x86_64; ; )

[Ccing Keith Marshall as the reporter of <https://savannah.gnu.org/bugs/?57725>]

Hi Eli,

> Gnulib's sys/socket.h has this:
>   # if @HAVE_WINSOCK2_H@
>   /* Include headers needed by the emulation code.  */
>   #  include <sys/types.h>
>   #  include <io.h>
>   #  if !GNULIB_defined_socklen_t
>   typedef int socklen_t;
>   #   define GNULIB_defined_socklen_t 1
>   #  endif
>   # endif
> This unconditionally defines socklen_t on MS-Windows systems as a
> signed int data type.  Why is this unconditional?

Earlier, it was unconditionally needed.

> This page:
>   https://pubs.opengroup.org/onlinepubs/007908799/xns/syssocket.h.html
> says:
>   <sys/socket.h> makes available a type, socklen_t, which is an
>   unsigned opaque integral type of length of at least 32 bits.

The page you cite is part of SUSv2. It has been superseded by POSIX,
first by the 2004 edition:
and then by the current edition:

Please update your bookmarks.

> So socklen_t could be an unsigned data type, which would then conflict
> with the above.
> And in fact mingw.org's MinGW recently changed the socklen_t data type
> to be unsigned int, which breaks compilation of Gnulib's
> sys_socket.c.  Is MinGW in error here?

Looking at the prototypes of the function inet_ntop [1]
it should be 'unsigned int' or 'size_t'.

Looking at the prototypes of the functions connect [2], accept [3], bind [4],
getpeername [5], getsockname [6], getsockopt [7], recvfrom [8], sendto [9],
setsockopt [10]
it should be 'int'.

But regardless how mingw defines 'socklen_t' (as 'int' or as 'unsigned int'),
none of these prototypes is POSIX compliant anyway, since all these prototypes
have the WSAAPI attribute.

So, gnulib should define socklen_t if and only if the system's header don't.
The code which does this is in m4/socklen.m4. I'm therefore applying the patch

[4] https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-bind

2020-06-29  Bruno Haible  <bruno@clisp.org>

        sys_socket: Don't define socklen_t if it is already defined on mingw.
        Reported by Keith Marshall <keith.d.marshall@ntlworld.com> in
        by Rahul Das <bokul_4u@yahoo.com> in
        and by Eli Zaretskii <eliz@gnu.org> in
        * lib/sys_socket.in.h (socklen_t): Remove definition.

diff --git a/lib/sys_socket.in.h b/lib/sys_socket.in.h
index 948d689..577947d 100644
--- a/lib/sys_socket.in.h
+++ b/lib/sys_socket.in.h
@@ -195,12 +195,7 @@ struct sockaddr_storage
 /* Include headers needed by the emulation code.  */
 #  include <sys/types.h>
 #  include <io.h>
-#  if !GNULIB_defined_socklen_t
-typedef int socklen_t;
-#   define GNULIB_defined_socklen_t 1
-#  endif
+/* If these headers don't define socklen_t, <config.h> does.  */
 # endif
 /* Rudimentary 'struct msghdr'; this works as long as you don't try to

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