[patch] LWG 2019 - std::isblank<C>(C, const std::locale&)

[Jonathan Wakely]

On 17/10/14 10:41 +0100, Jonathan Wakely wrote:
>http://cplusplus.github.io/LWG/lwg-defects.html#2019
>
>I've checked the relevant _ISblank/_ISBLANK/_CTYPE_B constant on all
>targets except VxWorks where I chose something that looks reasonable.
>Not all targets reserve a bit for isblank, but this way
>ctype_base::blank is always defined, but on some platforms with the
>same value as ctype_base::space. That means that on those targets
>isblank(c, loc) is equivalent to isspace(c, loc) which is not correct,
>but isn't completely crazy either.
>
>Some systems (bionic, newlib, netbsd, openbsd) do define a _B (or
>_CTYPE_B) constant, but as it says on netbsd:
>
>/*
>* isblank() is implemented as C function, due to insufficient bitwidth in
>* _ctype_.  Note that _B does not mean isblank - it means isprint && !isgraph.
>*/
>
>On those targets there is no bitmask corresponding to the isblank set.
>I don't know how to solve that without changing ctype_base::mask to a
>wider type, which I'm not planning on doing.
>
>N.B. on other BSDs (freebsd, darwin, dragonfly) _CTYPE_B *does*
>correspond to isblank. Portability is fun.
>
>Some implementations of ctype<char>::is(mask, char) and/or
>ctype<wchar_t>::do_is defined inline in config/os/*/ctype_inline.h
>need the ctype_base::blank mask, but those files get included by C++98
>code, so for some targets ctype_base::blank is always defined even in
>C++98 mode. Solving that is too difficult.
>
>Tested x86_64-linux, with --enable-clocale={gnu,generic}
>and also by hacking configure.host to use config/os/generic, and also
>tested on x86_64-netbsd5.1 and x86_64-dragonfly3.6. Something will
>probably break on a target I didn't test, but should be easy to fix.
>
>I plan to commit this later today.

Committed to trunk.