Call to locale_charset within wcwidth

[Gavin Smith]

I am working on a program that uses wcwidth from gnulib on many
characters in a buffer, however this is reported to be slow under some
platforms.[1]

The reason appears to be the call to locale_charset within the wcwidth
implementation. I found some discussion of speeding this up in the
bug-gnulib archives [2][3], has there been any progress on this?

The charset could be cached either in wcwidth itself, or there could
be some caching in locale_charset.

It appears you can have thread-local variables with gcc using
"__thread", for example, "static __thread const char *encoding". (I
don't know about other compilers.) Would something like this work? As
well as threads, updating the cached encoding when the encoding
changes would be a problem.

[1] http://lists.gnu.org/archive/html/bug-texinfo/2015-01/msg00004.html
[2] http://lists.gnu.org/archive/html/bug-gnulib/2011-12/msg00083.html
[3] http://lists.gnu.org/archive/html/bug-gnulib/2013-12/msg00087.html