On 9 January 2017 at 15:52, Saleem Abdulrasool wrote:
> libc++ would like to support both the itanium and the Microsoft ABIs. This
> leaks into the header through type_info. The macro would help correctly
> build and configure checks to ensure that the ABI matches.
>
> Having the macro defined would allow the headers to inject code into the
> user application to ensure the ABI matches at link time without having the
> user specify the ABI they believe the compiler to be using.

You don't need a macro defined by SD-6 to do that though, any private
macro that is known by the compiler and the runtime will work for that
purpose. It doesn't need to be recommended by SD-6 unless users are
expected to make use of it.