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I don't think the problem can be solved once and forall. In
fact, I'm certain that the glib code is incorrect on some
systems. For example, has it been tested on VMS, with its
three different floatin point formats?

I don't know whether linking with glib is a good idea. I'd
happily accept a patch that supports glibc only, or one that
tries for fall back to C++ std::locale on systems that
support linking C++ code into C applications. Since the bug
report was triggered through gtk problems, I expect that
these can all be solved by linking with glib - using glib on
a gtk installation should work fine.