\begin{describe}[SodClass]{cls}
{[nick = cls, link = SodObject] \\
- class SodClass : SodObject \{ \\ \ind
+ class SodClass: SodObject \{ \\ \ind
const char *name; \\
const char *nick; \\
size_t initsz; \\
@<type>_n @<slot>_n; \-\\
\} $c$; \-\\
\} $c$; \\
- struct $H$__ichain_$h$ $h$; \\
+ struct $A$__ichain_$h$ $a$; \\
\quad$\vdots$ \-\\
\} $h$; \\
union $B$__ichainu_$i$ $i$; \\
\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
In general, the vtables for the different chains will have \emph{different}
structures.
-The instance layout split neatly into disjoint chains. This is necessary
+The instance layout splits neatly into disjoint chains. This is necessary
because each @|ichain| must have as a prefix the @|ichain| for each
superclass in the same chain, and each slot must be stored in exactly one
place. The layout of vtables doesn't have this second requirement: it
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}
\item Let $N$ be the metaclass of $A$. Examine the superclass chains of $N$
in order of decreasing specificity of their most-specific classes. Let $J$
- be the chain head of such a chain, and let $Q$ be the most specific
- superclass of $M$ in the same chain as $J$. Then, if there is currently no
- class pointer of type $Q$, then add a member
+ be the chain head of such a chain. If there is currently no class pointer
+ for the chain headed by $J$, then add a member
\begin{prog}
const $Q$ *_cls_$j$;
\end{prog}
to the vtable pointing to the appropriate @|islots| structure within $M$'s
- class object.
+ class object, where $Q$ is the most specific superclass of $M$ in the same
+ chain as $J$.
\item Examine the superclass chains of $A$ in order of decreasing specificity
of their most-specific classes. Let $I$ be the chain head of such a chain.
@<type>_n @<arg>_n? \+\\
@<type>_{n+1} @<kw>_{n+1} @[= @<dflt>_{n+1}@],
$\ldots$,
- @<type>_m @<kw>_m @[= @<dflt>_m@]);
+ @<type>_{n'} @<kw>_{n'} @[= @<dflt>_{n'}@]);
\end{prog}
two entry points are defined: the usual `main' entry point which accepts a
variable number of arguments, and a `valist' entry point which accepts an
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 --------------------------------------------------
~mdw / sod / blobdiff