[Bug c/7652] -Wswitch-break : Warn if a switch case falls through

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=7652

--- Comment #24 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Matthew Woehlke from comment #22)
>     [[gcc:fallthrough]] // suppress warning for fall-through to 'case C'

N.B. the attribute-namespace for GNU extensions is "gnu"

I agree that the attribute is essential before such warning could be enabled by
-Wall