Signedness of wchar_t and wint_t leads to problems with gcc -Wsign-conversion

[Zack Weinberg]

On Mon, Nov 21, 2016 at 9:37 AM, Andreas Schwab <schwab@suse.de> wrote:
> On Nov 21 2016, Zack Weinberg <zackw@panix.com> wrote:
>
>> However, it is not clear to me that actual implementations honor that
>> requirement.  Consider the case where wchar_t is signed short (this
>> hypothetical implementation is limited to the BMP), wint_t is signed
>> int, and WEOF == ((wint_t)-1).  Then (wint_t)U+FFFF is
>> indistinguishable from WEOF.  Yes, U+FFFF is a reserved codepoint, but
>> it's still wrong for it to collide.
>
> WEOF must be defined "to a constant expression of type wint_t whose
> value does not correspond to any member of the extended character set."
> This guarantees that there cannot be a conflict with valid values of
> wchar_t.

 "It is not clear to me that actual implementations honor that requirement."