[Issue 24132] ImportC: Add support for wchar_t, char16_t, char32_t

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24132

Adam Wilson <flyboynw at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|ImportC: Add support for    |ImportC: Add support for
                   |wchar_t                     |wchar_t, char16_t, char32_t

--- Comment #2 from Adam Wilson <flyboynw at gmail.com> ---
(In reply to ryuukk_ from comment #1)
> Sounds like an easy PR to do, add the define here:
> 
> https://github.com/dlang/dmd/blob/master/druntime/src/importc.h

It's not *quite* that simple. wchar_t is #define as an unsigned short in C, and
either an unsigned short *or* an intrinsic type in C++. This means that when
the preprocessor runs it emits an unsigned short. However, most C preprocessors
have a switch that treat wchar_t as an intrinsic type instead of "typedef
wchar_t unsigned short" However, the current ImportC implementation does not
support this and vomits up errors when you try to use it.

What we need is the ability for ImportC to recognize wchar_t, char16_t, and
char32_t *after* the preprocessor has run so that ImportC can emit the
appropriate char/wchar/dchar types.

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