On Tuesday we discussed a few feature test macros that we want added at this meeting.

At our lunch meeting, we suggested that the language one be named specially because for these features end-users need to test the library one to know if they have both the language feature and the library facility needed to use it. The language macro is primarily of use to library implementors.

__cpp_lang_destroying_delete
__cpp_destroying_delete
__cpp_lang_destroying_delete
__cpp_destroying_delete

LWG did not like this approach. They want all library macros, which require a header to be included before they can be used, to begin with “__cpp_lib”. They also found “lang” no be insufficiently clear as a way to suggest that end-users should not use that macro.

LWG would like to use:

__cpp_impl_destroying_delete
__cpp_lib_destroying_delete

__cpp_impl_destroying_delete
__cpp_lib_destroying_delete

These changes are okay with me.

What do you think of them?

The paper that describes the changes is available here:

http://wiki.edg.com/pub/Wg21sandiego2018/CoreWorkingGroup/d1353r0.html

John.