https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105362
--- Comment #2 from Pavel M <pavel.morozkin at gmail dot com> ---
I do believe that evaluation of constant expressions in conditional inclusion
is done according to the rules of constant expressions ("except that ...", see
C11, 6.10.1/1). Hence, I expect the same diagnostics in all the places where
constant expressions may be used.
