\end{prog}
for each of $C$'s superclasses $A$ in the same chain in some (unimportant)
order. The (somewhat obtuse) purpose of this union is to engage the `common
-initial sequence' rule of \cite[6.5.2.3]{FIXME:C99}.
+initial sequence' rule of \cite[6.5.2.3]{ISO:1990:IIP,ANSI:1999:AII}.
\subsubsection{The ichain structure}
The @|ichain| structure contains (in order), a pointer
This is mostly an irrelevant detail, whose purpose is to defend against
malicious compilers: pointers are always to one of the inner @|vt|
-structures. It's important only because it's the outer @|vtu| union which is
-exported by name. Specifically, for each chain of $C$'s superclasses there is
-an external object
+structures. It's important only because it's the outer @|vtu| union which is
+exported by name. Specifically, for each chain of $C$'s superclasses there
+is an external object
\begin{prog}
const union $A$__vtu_$i$ $C$__vtable_$i$;
\end{prog}
Finally, the class object is defined as
\begin{prog}
extern const struct $R$__ilayout $C$__classobj; \\
- \#define $C$__class (\&$C$__classobj.$j$.$r$)
+ \#define $C$__class (\&$C$__classobj.$j$.$r$) \\
+ \#define $C$__cls_$k$ (\&$C$__classobj.$k$.$n$) \\
+ \quad$\vdots$
\end{prog}
The exported symbol @|$C$__classobj| contains the entire class instance.
This is usually rather unwieldy. The macro @|$C$__class| is usable as a
pointer of type @|const $R$~*|, where $R$ is the root metaclass of $C$, i.e.,
the metaclass of the least specific superclass of $C$; usually this is
-@|const SodClass~*|.
+@|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.
+
%%%----- That's all, folks --------------------------------------------------