On Tue, 30 Jul 2024 at 23:49, Giuseppe D'Angelo <giuseppe.dang...@kdab.com> wrote: > > Hello, > > On 30/07/2024 15:04, Jonathan Wakely wrote: > > On Mon, 29 Jul 2024 at 21:58, Giuseppe D'Angelo wrote: > >> > >> Hi, > >> > >> And this is the corresponding change libstdc++. > > > > Thanks for the patch. > > Again, thanks for the guidance, should be all fixed.
The new built-in won't be available when compiling with older versions of Clang, so it needs to be used conditionally. I think the feature test macro should only be defined if the built-in is available. See the version.def entry for bit_cast, for example. If __cpp_lib_is_virtual_base_of depends on __has_builtin, then that will do the right thing for #ifdef __cpp_lib_is_virtual_base_of in <type_traits>.
