+@|const SodClass~*|. For each chain of $C$'s metaclass, a macro
+@|$C$__cls_$k$| is defined, usable as a pointer of type @|const $N$~*|, where
+$K$ and $N$ are the chain's head and tail classes (i.e., the least- and
+most-specific classes in the chain) respectively; this macro is
+\emph{omitted} if $N = R$, i.e., in the common case where $C$'s metaclass is
+precisely the root metaclass, since the existing @|$C$__class| macro is
+already sufficient.
+