Re: sys/socket.h on mingw32 vs socklen (resend)

[Simon Josefsson]

Bruno Haible <address@hidden> writes:

> Simon Josefsson wrote on 2005-12-17:
>> The sys_socket module below will create a sys/socket.h file, primarily
>> for mingw32, but it could be extended for other systems or missing
>> sys/socket.h features in the future.
>> 
>> This would solve the problem of accessing sys/socket.h stuff in
>> applications.
>
> I like this idea. So we can get rid of #if HAVE_SYS_SOCKET_H in many places.

That's another feature I didn't think of.  I like it.

>> Index: lib/socket_.h
>> ===================================================================
>> RCS file: lib/socket_.h
>> diff -N lib/socket_.h
>> --- /dev/null        1 Jan 1970 00:00:00 -0000
>> +++ lib/socket_.h    16 Dec 2005 15:04:41 -0000
>> @@ -0,0 +1,26 @@
>> +/* Provide a sys/socket header file for systems lacking it (read: mingw32).
>> +   Copyright (C) 2005 Free Software Foundation, Inc.
>> +   Written by Simon Josefsson.
>> +
>> +   This program is free software; you can redistribute it and/or modify
>> +   it under the terms of the GNU General Public License as published by
>> +   the Free Software Foundation; either version 2, or (at your option)
>> +   any later version.
>> +
>> +   This program is distributed in the hope that it will be useful,
>> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> +   GNU General Public License for more details.
>> +
>> +   You should have received a copy of the GNU General Public License
>> +   along with this program; if not, write to the Free Software Foundation,
>> +   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
>> +
>> +#ifndef _SYS_SOCKET_H
>> +#define _SYS_SOCKET_H
>> +
>> +#if HAVE_WINSOCK2_H
>> +# include <winsock2.h>
>> +#endif
>
> Comments should indicate for which platforms this file is meant to be useful
> and on which platforms you expect <winsock2.h> to be present. (Currently only
> mingw, I think?)
>
> Also, this should include <ws2tcpip.h>, so that socklen_t is defined
> (and a type redefinition error is avoided when the user includes 
> <ws2tcpip.h>).

I added:

/* This file is supposed to be used on platforms that lack
   sys/socket.h.  It is intended to provide definitions and prototypes
   needed by an application.

   Currently only mingw32 is supported, which has the header files
   winsock2.h and ws2tcpip.h that declare the sys/socket.h definitions
   we need. */

>> +# We need the following in order to create <sys/socket.h> when the system
>> +# doesn't have one that works with the given compiler.
>> +sys/socket.h: socket_.h
>> +    mkdir sys
>
> Create the directory only when it does not exist. (Otherwise the user is
> blocked if he happens to press Ctrl-C after the sys directory has been
> created but before sys/socket.h is present.)

Done.

>> +    cp $(srcdir)/socket_.h address@hidden
>> +    mv address@hidden $@
>> +MOSTLYCLEANFILES += sys/socket.h sys/socket.h-t
>> +
>> +mostlylocal-clean:
>
> Should be mostlyclean-local, not mostlylocal-clean.

Oops, thanks.

>> +    rmdir sys
>
> Remove the directory only when it exists and is empty. (Some systems create
> files in your directories without being asked for, e.g. .DS_Store on MacOS X.)

How do I test for that in a portable way?

>> However, it does not solve the problem of accessing sys/socket.h
>> inside autoconf tests, and in particular from the socklen
>> module.
>> 
>> Currently the socklen test fail on mingw32:
>> 
>> checking for socklen_t... no
>> checking for socklen_t equivalent...
>> configure: error: Cannot find a type to use in place of socklen_t
>> 
>> because:
>> 
>> configure:3814: i586-mingw32msvc-gcc -c -g -O2 conftest.c >&5
>> conftest.c:23:26: sys/socket.h: No such file or directory
>> 
>> I can think of three solutions:
>> 
>> 0) In socklen, default the type to 'int' instead of aborting.  This
>>    would be compatible with mingw32, they use 'typedef int socklen_t'.
>>    The patch below implement this.
>> 
>> 1) Fix the socklen M4 test to check for the existence of socket.h,
>>    winsock2.h and ws2tcpip.h and include the appropriate headers when
>>    needed.  This has the problem that the application will have to
>>    include the non-POSIX headers too, if they need socklen_t.  The
>>    patch below implement this.
>> 
>> 2) Create the gnulib sys/socket.h directly in the M4 macro, and set up
>>    CFLAGS to include the gnulib directory during ./configure.  This
>>    has the problem that all modules invoked before the sys_socket
>>    module will not work.  It seem wrong for those modules to depend on
>>    "sys_socket", because sys/socket.h is a POSIX header which most
>>    tests could assume.
>
> A fourth solution is
>
> 3) Set some configure variables during sys_socket_h.m4 that are used in the
> socklen.m4 tests.

That would make socklen.m4 a bit more complex, but seem doable.

I now realized that the problem I mentioned in 1) isn't really a
problem.  Applications that need socklen_t should probably depend on
the sys/socket.h module.  Perhaps the socklen_t module should depend
on the sys_socket module?  That would make things the easiest for the
application.

> Ad 0): I don't like this, because socklen_t values are passed through a
> pointer, and if the argument type of getpeername() is not 'int *', the
> program will break horribly. Don't make the autoconf test less reliable than
> it is now.

Agreed.

> Ad 1): Having socklen.m4 check for ws2tcpip.h is probably unavoidable, since
> it is this header file which defines socklen_t on mingw, and winsock2.h 
> doesn't.
> But let the sys_socket_h module do the rest, and let user programs use
> only <sys/socket.h>. I don't like the two gnulib modules be so tied together,
> but can't see a better solution.

Ok.

> Ad 2): Creating a file directly from within an m4 macro looks wrong. Reasons:
> - Filenames don't belong in .m4 files.
> - The removal of the file must be triggered by "make distclean", i.e. from a
>   Makefile. Then it's more symmetrical if the file is created by the same
>   Makefile.

Agreed.

>> I think 0 and 1 should be done, together with installing the
>> sys_socket module.
>
> I think a mix of 1) and 3) is the best.

Agreed.

>> Possibly, socklen should not test for ws2tcpip.h.
>
> I think it needs to.

Unless the socklen module depend on the sys_socket module, yes.

Updated patch below.  I haven't fixed the rmdir problem and the
socklen issue, but I believe those can be handled later.

Thanks,
Simon

Index: lib/socket_.h
===================================================================
RCS file: lib/socket_.h
diff -N lib/socket_.h
--- /dev/null   1 Jan 1970 00:00:00 -0000
+++ lib/socket_.h       9 Jan 2006 16:24:40 -0000
@@ -0,0 +1,37 @@
+/* Provide a sys/socket header file for systems lacking it (read: mingw32).
+   Copyright (C) 2005, 2006 Free Software Foundation, Inc.
+   Written by Simon Josefsson.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+#ifndef _SYS_SOCKET_H
+#define _SYS_SOCKET_H
+
+/* This file is supposed to be used on platforms that lack
+   sys/socket.h.  It is intended to provide definitions and prototypes
+   needed by an application.
+
+   Currently only mingw32 is supported, which has the header files
+   winsock2.h and ws2tcpip.h that declare the sys/socket.h definitions
+   we need. */
+
+#if HAVE_WINSOCK2_H
+# include <winsock2.h>
+#endif
+#if HAVE_WS2TCPIP_H
+# include <ws2tcpip.h>
+#endif
+
+#endif /* _SYS_SOCKET_H */
Index: m4/sys_socket_h.m4
===================================================================
RCS file: m4/sys_socket_h.m4
diff -N m4/sys_socket_h.m4
--- /dev/null   1 Jan 1970 00:00:00 -0000
+++ m4/sys_socket_h.m4  9 Jan 2006 16:24:40 -0000
@@ -0,0 +1,19 @@
+# sys_socket_h.m4 serial 1
+dnl Copyright (C) 2005 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Simon Josefsson.
+
+AC_DEFUN([gl_HEADER_SYS_SOCKET],
+[
+  AC_CHECK_HEADERS_ONCE([sys/socket.h])
+  if test $ac_cv_header_sys_socket_h = yes; then
+    SYS_SOCKET_H=''
+  else
+    AC_CHECK_HEADERS_ONCE([winsock2.h])
+    SYS_SOCKET_H='sys/socket.h'
+  fi
+  AC_SUBST(SYS_SOCKET_H)
+])
Index: modules/sys_socket
===================================================================
RCS file: modules/sys_socket
diff -N modules/sys_socket
--- /dev/null   1 Jan 1970 00:00:00 -0000
+++ modules/sys_socket  9 Jan 2006 16:24:40 -0000
@@ -0,0 +1,36 @@
+Description:
+A <sys/socket.h> for systems lacking it.
+(Currently only useful for mingw32, it will simply include winsock2.h.)
+
+Files:
+lib/socket_.h
+m4/sys_socket_h.m4
+
+Depends-on:
+
+configure.ac:
+gl_HEADER_SYS_SOCKET
+
+Makefile.am:
+BUILT_SOURCES += $(SYS_SOCKET_H)
+EXTRA_DIST += socket_.h
+
+# We need the following in order to create <sys/socket.h> when the system
+# doesn't have one that works with the given compiler.
+sys/socket.h: socket_.h
+       test -d sys || mkdir sys
+       cp $(srcdir)/socket_.h address@hidden
+       mv address@hidden $@
+MOSTLYCLEANFILES += sys/socket.h sys/socket.h-t
+
+mostlyclean-local:
+       rmdir sys
+
+Include:
+#include <sys/socket.h>
+
+License:
+LGPL
+
+Maintainer:
+Simon Josefsson