[PATCH] PR libstdc++/80624 satisfy invariant for char_traits<char16_t>::eof()

[Florian Weimer via gcc-patches]

On 05/05/2017 07:05 PM, Jonathan Wakely wrote:
> As discussed at http://stackoverflow.com/q/43769773/981959 (and kinda
> hinted at by http://wg21.link/lwg1200) there's a problem with
> char_traits<char16_t>::eof() because it returns int_type(-1) which is
> the same value as u'\uFFFF', a valid UTF-16 code point.

I think the real bug is that char_traits<char16_t>::int_type is just 
plain wrong.  It has to be a signed integer, and capable of representing 
values in the range 0 .. 65535.  char_traits<char32_t> has a similar 
problem.  char_traits<wchar_t> should be fine on glibc because WEOF is 
reserved, something that is probably not the case for char32_t.

Thanks,
Florian