I'm not sure how I tested MOZ_FOR_EACH in bug 1368932, but it turns out
it doesn't work with an empty list, despite
MOZ_PASTE_PREFIX_AND_ARG_COUNT now supporting 0 arguments.
Macros can be tricky, and it ends up being easier to make things work
cross-compiler with a separate macro that does the counting, and
(re)building MOZ_PASTE_PREFIX_AND_ARG_COUNT on top of that. Then
MOZ_FOR_EACH ends up working as expected with an empty list.
So this adds a MOZ_ARG_COUNT macro that counts the number of variadic
arguments it's given, and derives MOZ_PASTE_PREFIX_AND_ARG_COUNT from
it.
And this adds a testcase validating that MOZ_FOR_EACH works properly
with an empty list as a result.
--HG--
extra : rebase_source : 309371d87bd1561fbd2153f44fc1256185045d23
At the same time, remove the MOZ_STATIC_ASSERT_VALID_ARG_COUNT, which
doesn't actually work for more than 50 arguments(*), and which is now not
useful to detect 0 arguments.
(*) the build fails, but not directly thanks to the static_assert it
expands to.
--HG--
extra : rebase_source : 8f0fe7b352c89b5a3ec87f42ef5464c370c362ef
