[kps]

C11 standardizes variadic macros — see §6.10.3 Macro replacement http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf

[codys]

Yes, even c99 has them IIRC.

The issue that was called out, however, was the use of "FOO(x, ## __VA_ARGS__)".

GNU C has an extension that causes the ',' to be removed if __VA_ARGS__ is empty. AFAIK, it is not standard.