A (builtin) function, returning bit offset for bitfields within structs, could
be useful to pass bit "addresses" as function parameters.
In analogy to offsetof()/sizeof(), a similar function returning number of bits
of a bitfield could be created, too, although it would be less useful than the
(I posted the same feature request to the gcc tracker, too, http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45881 ).