Re: [bug-gnulib] wcwidth on mingw

[Bruno Haible]

Eric Blake wrote:
> Using cygwin to cross-compile to mingw, I got:
> 
> $ CFLAGS='-Wall -O2' CC='gcc -mno-cygwin' ./gnulib-tool --test mbchar
> ...
> gcc -mno-cygwin -DHAVE_CONFIG_H -I. -I../../lib -I..     -Wall -O2 -
> c ../../lib/mbchar.c
> In file included from ../../lib/mbchar.c:24:
> ../../lib/mbchar.h: In function `mb_width_aux':
> ../../lib/mbchar.h:243: warning: implicit declaration of function `wcwidth'
> rm -f libgnu.a
> 
> I note that mbswidth.c takes precautions to ensure wcwidth exists;
> should we break that out into a wcwidth module and make both mbchar and
> mbswidth depend on it?

This would make sense, yes. I'm normally not fond of major changes
that avoid an "implicit declaration of function" warning of a function
that returns 'int' anyway. But here we have gone through the trouble
of doing it right already in mbswidth.c - why not reuse this technique.

> This patch is my first cut at it; Bruno, I think you would be better as  
> the maintainer since I broke it out of your mbswidth.

Agreed.

> --- MODULES.html.sh   21 Jun 2006 10:00:08 -0000      1.117
> +++ MODULES.html.sh   27 Jun 2006 15:42:53 -0000
> @@ -1775,6 +1775,7 @@
>    func_module mbiter
>    func_module mbuiter
>    func_module mbfile
> +  func_module wcwidth
>    func_end_table
>  
>    element="Support for systems lacking POSIX:2001"

I think this belongs in section "Support for systems lacking POSIX:2001",
not in section "Extra functions based on ISO C 99".

> Index: lib/wcwidth.h
> ===================================================================
> RCS file: lib/wcwidth.h
> diff -N lib/wcwidth.h
> --- /dev/null 1 Jan 1970 00:00:00 -0000
> +++ lib/wcwidth.h     27 Jun 2006 15:42:54 -0000
> @@ -0,0 +1,34 @@
> +/* Determine the number of screen columns needed for a character.
> +   Copyright (C) 2000-2006 Free Software Foundation, Inc.
> +
> +   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 HAVE_DECL_WCWIDTH
> +"this configure-time declaration test was not run"
> +#endif
> +#if !HAVE_DECL_WCWIDTH
> +# ifdef      __cplusplus

No tabs here, please.

> +extern "C"
> +# endif
> +int wcwidth ();
> +#endif
> +
> +#ifndef wcwidth
> +# if !HAVE_WCWIDTH
> +/* wcwidth doesn't exist, so assume all printable characters have
> +   width 1.  */
> +#  define wcwidth(wc) ((wc) == 0 ? 0 : iswprint (wc) ? 1 : -1)
> +# endif
> +#endif

Here I would use an inline function. A macro is fine for limited use,
as in mbswidth.c, but for a .h file, an inline function is safer.

Also, for iswprint to be usable here, you need this code:

--------------------------------------------------------------------------
/* Solaris 2.5 has a bug: <wchar.h> must be included before <wctype.h>.  */
#if HAVE_WCHAR_H
/* Tru64 with Desktop Toolkit C has a bug: <stdio.h> must be included before
   <wchar.h>.
   BSD/OS 4.1 has a bug: <stdio.h> and <time.h> must be included before
   <wchar.h>.  */
# include <stdio.h>
# include <time.h>
# include <wchar.h>
#endif

/* Get iswprint().  */
#if HAVE_WCTYPE_H
# include <wctype.h>
#endif
#if !defined iswprint && !HAVE_ISWPRINT
# define iswprint(wc) 1
#endif
--------------------------------------------------------------------------

> --- /dev/null 1 Jan 1970 00:00:00 -0000
> +++ m4/wcwidth.m4     27 Jun 2006 15:42:54 -0000
> @@ -0,0 +1,34 @@
> +# wcwidth.m4 serial 1
> +dnl Copyright (C) 2006 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 autoconf tests required for use of mbswidth.c
> +
> +AC_DEFUN([gl_WCWIDTH],

I would call this macro gl_FUNC_WCWIDTH, since it provides only the
function 'wcwidth'.

> +[
> +  AC_CHECK_FUNCS([wcwidth])

An AC_REQUIRE([AC_GNU_SOURCE]) needs to be inserted here, for glibc
systems.

Thanks!

Bruno