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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libstdc++/98725] Review what is disabled in libstdc++ by
 --disable-wchar_t
Date: Fri, 08 Oct 2021 23:31:31 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98725

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
We could make codecvt<wchar_t, char, mbstate_t> work if we assume that wcha=
r_t
contains UTF-32 or UTF-16 (depending on the size of wchar_t) and reuse the
specializations for char32_t and char16_t. Those specializations are
implemented entirely in libstdc++ with no libc help.

It's unclear (to me) whether --disable-wchar_t is used explicitly to produc=
e a
smaller libstdc++ build, without wchar_t instantiations, or is just used
implicitly on systems where the libc <wchar.h> support is missing. So it's =
hard
to know whether "emulate wchar_t support in terms of UTF-32" is desirable, =
or
if that would frustrate users explicitly trying to get a smaller library.

Presumably anybody who wants a smaller library would also want to disable t=
he
codecvt facets for char32_t and char16_t, but nobody has requested that.

I'm not going to spend any more time on it after enabling wide strings and =
some
type traits.=