indenting GLib attributes

Hello all-
I would like to be able to use GNU indent with some header files that
have GLib-style attribute defines.  GLib defines macros like these

#define G_GNUC_PURE __attribute__((__pure__))
#define G_GNUC_MALLOC __attribute__((__malloc__))
#define G_GNUC_NO_INLINE __attribute__((noinline))
and similarly for printf, noreturn, const, unused, etc

Would it be easy to make that sort of mod? Any hints?

Thanks,
Mike Gran