Clang has been providing __is_void for a very long time now, and is
definitely compatible with libstdc++. Does defining this builtin cause a
problem? Might be that the lookup rules for builtins are different or
something.

https://clang.llvm.org/docs/LanguageExtensions.html#type-trait-primitives

On Sat, 25 Mar 2023 at 15:08, Ken Matsui via Gcc <gcc@gcc.gnu.org> wrote:

> Hi,
>
> I am working on the GSoC project, "C++: Implement compiler built-in
> traits for the standard library traits".
>
> Built-in trait naming simply adds two underscores (__) to the original
> trait name. However, the same names are already in use for some
> built-in traits, such as is_void, is_pointer, and is_signed.
>
> For example, __is_void is used in the following files:
>
> * gcc/testsuite/g++.dg/tm/pr46567.C
> * libstdc++-v3/include/bits/cpp_type_traits.h
>
> In this case, are we supposed to change the existing same name in the
> code to something like ____is_void (four underscores)? Or is it better
> to break the naming convention of built-in traits like
> __is_void_builtin?
>
> Sincerely,
> Ken Matsui
>