USE_FEATURES complete?

[Aleksey Cheusov <cheusov%tut.by@localhost>]

I'm trying to build program that uses setprogname and getprogname
thet are not portable and are not available on Linux.
As far as I understand all I need to do this is the following

   USE_FEATURES+=    getprogname setprogname

line in Makefile.
But this doesn't work.

Are ALL features implemented?
features/features-vars.mk lists both 'getprogname' and 'setprogname'
as supported.

-- 
Best regards, Aleksey Cheusov.