From: Bruno Haible <bruno@clisp.org>
To: bug-gnulib@gnu.org, cygwin@cygwin.com
Subject: Re: 16-bit wchar_t on Windows and Cygwin
Date: Thu, 3 Feb 2011 11:48:48 +0100
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Corinna Vinschen wrote:
> isn't wwchar_t equivalent to wint_t on all
> platforms?  On UCS-4 platforms sizeof(wint_t) == sizeof(wchar_t) == 4
> because there's no reason to make it bigger.  On UCS-2 and UTF-16
> platforms sizeof(wint_t) == 4 because it must be able to hold EOF as
> well.  So, why not just use the wint_t type for the time being?

The "must be able to hold WEOF as well" argument holds for the argument
type of iswwalpha.  If we were to call it 'wwint_t', it would be the same as
'wint_t', yes. For this reason, we don't need a separate type 'wwint_t'.

But 'wwchar_t' is the base type for wide wide character _arrays_.
Such arrays don't need to hold the WEOF value. On AIX platforms, where
wchar_t[] is the UCS-2 encoding, wwchar_t[] can be synonymous to it.
There is no need to make wwchar_t 32 bits wide on these platforms.

So, my current code looks like this:

# if (defined _WIN32 || defined __WIN32__) || defined __CYGWIN__
/* Define 'wwchar_t' as a type that
     - can hold 32 bits, unlike wchar_t which can hold only 16 bits,
     - promotes to 'wint_t' under the default argument promotions.  */
typedef wint_t wwchar_t; /* actually 'unsigned int' or 'uint32_t' */
# else
typedef wchar_t wwchar_t;
# endif

Bruno
-- 
In memoriam Buddy Holly <http://en.wikipedia.org/wiki/Buddy_Holly>

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