Re: [9fans] wchar_t in ANSI C (was "Announce: port")

["rob pike, esq." <rob@plan9.bell-labs.com>]

> Sounds like somebody who doesn't use them enough to know.
> wchar_t is closely analogous to rune.
> The real problem is that "char" is inadequate for encoding a character,
> largely a consequence of Dennis chiming in on the sizeof(char)==1 side.

I don't want to debate whether sizeof(char) should be 1, but I do
think you're being too forgiving about wchar_t, at least in the
original standard.  There were too many holes in the standard, such as
no defined format for printing wchar_t strings, no defined conversion
between strings of either type (just of individual characters) and no
defined input method.  In short, no stdio support!  Too much last-minute
committee design, I find.

Footnotes 119 and 122 in the I/O section of the standard (printf,
scanf) both read: "No special provisions are made for multibyte
characters."  Give me a break!  How hard would it have been to define
%lc and %ls, for instance?

The answer is surprisingly subtle, and is answered in my next paragraph.

The issue that cheeses me most still remains even in the new standard:
the clumsiness of converting in the face of conversion errors such as
malformed UTF-8, which turn up a lot when you're scanning binary data
looking for strings, or just get handed something like Latin-1 when
you're expecting UTF-8.  Most programs (e.g grep) can do nothing
useful in the face of errors except barge on, but the ANSI C standard
makes the standard character processing loop a real mess.  It also
makes scanf("%ls or %lc") impossible to write consistently with the
rest of the standard, since you need to stop if there's a conversion
error, almost never what you want.  This issue is a matter of taste,
but I feel it's done wrong.  The Plan 9 model, with the concept of an
"Error Rune", makes it easy to ignore errors but also easy to handle
them, as you decide.  Plan 9's is a much better model because it was a
model born of experience rather than design without implementation.

I reiterate that the error handling issue is one of taste, but that
there is no excuse for omitting wchar_t support in stdio.

We wrote about this in our UTF paper
	http://plan9.bell-labs.com/sys/doc/utf.pdf .html .ps
(The .html version has some character set awkwardness!).  If we could
have used ANSI C's design for wide characters, we would have, but it
was inadequate.

-rob