Re: iswxxxxx/towxxxer and Unicode

[Paul Eggert <eggert at twinsun dot com>]

   From: Ulrich Drepper <drepper@redhat.com>
   Date: 18 Jul 2000 11:52:25 -0700

   Bruno Haible <haible@ilog.fr> writes:

   > U0000 is has a very particular meaning: it says "the C string ends
   > here". This makes it a control character.

   No.  This means NUL must not be passed to any of these functions.

True, but NUL has more meanings than just "the C string ends here".
All the standards I've seen say that NUL is a control character.  For
example, the latest draft (draft 3) of the next version of POSIX says
that NUL is a control character in the POSIX locale; see its
xbdtext.pdf, page 147.  Unicode 3.0 also says that NUL is a control
character; see page 337 of <http://charts.unicode.org/PDF/U0000.pdf>.
And the GNU coding standards

Standards aside, U0000 (ASCII NUL) has been a control character in
practice for at least 30 years.  I personally used NUL as a control
character on a Teletype Model 33 in 1970, where its control behavior
was hardwired into the paper tape reader.

If a test suite claims that NUL is not a control character, then the
test suite must be buggy.