[PATCH 1/3]: C N2653 char8_t: Language support

[Joseph Myers]

On Sun, 6 Jun 2021, Tom Honermann via Gcc-patches wrote:

> When -fchar8_t support is enabled for non-C++ modes, the _CHAR8_T_SOURCE macro
> is predefined.  This is the mechanism proposed to glibc to opt-in to
> declarations of the char8_t typedef and c8rtomb and mbrtoc8 functions proposed
> in N2653.  See [2].

I don't think glibc should have such a feature test macro, and I don't 
think GCC should define such feature test macros either - _*_SOURCE macros 
are generally for the *user* to define to decide what namespace they want 
visible, not for the compiler to define.  Without proliferating new 
language dialects, __STDC_VERSION__ ought to be sufficient to communicate 
from the compiler to the library (including to GCC's own headers such as 
stdatomic.h).

-- 
Joseph S. Myers
joseph@codesourcery.com