instances have the basic structure of a @|struct sod_instance|.
\begin{describe}[struct sod_instance]{type}
- {struct sod_instance \{ \\ \ind
- const struct sod_vtable *_vt; \- \\
+ {struct sod_instance \{ \\ \ind
+ const struct sod_vtable *_vt; \-\\
\};}
The basic structure of all instances. Members are as follows.
\end{describe}
\begin{describe}[struct sod_vtable]{type}
- {struct sod_vtable \{ \\ \ind
- const SodClass *_class; \\
- size_t _base; \- \\
+ {struct sod_vtable \{ \\ \ind
+ const SodClass *_class; \\
+ size_t _base; \-\\
\};}
A vtable contains static metadata needed for efficient conversions and
\begin{figure}[tbp]
\begin{tabular}{p{10pt}p{10pt}}
\begin{nprog}
- struct SodObject__ilayout \{ \\ \ind
- union \{ \\ \ind
- struct SodObject__ichain_obj \{ \\ \ind
- const struct SodObject__vt_obj *_vt; \- \\
- \} obj; \- \\
- \} obj; \- \\
+ struct SodObject__ilayout \{ \\ \ind
+ union \{ \\ \ind
+ struct SodObject__ichain_obj \{ \\ \ind
+ const struct SodObject__vt_obj *_vt; \-\\
+ \} obj; \-\\
+ \} obj; \-\\
\};
\end{nprog}
&
\begin{nprog}
- struct SodObject__vt_obj \{ \\ \ind
- const SodClass *_class; \\
- size_t _base; \\
- struct SodObject__vtmsgs_obj \{ \\ \ind
- void (*init)(SodObject *me, ...); \\
- void (*init__v)(SodObject *me, va_list); \\
- int (*teardown)(SodObject *me); \- \\
- \} obj; \- \\
+ struct SodObject__vt_obj \{ \\ \ind
+ const SodClass *_class; \\
+ size_t _base; \\
+ struct SodObject__vtmsgs_obj \{ \\ \ind
+ void (*init)(SodObject *me, ...); \\
+ void (*init__v)(SodObject *me, va_list); \\
+ int (*teardown)(SodObject *me); \-\\
+ \} obj; \-\\
\};
- \end{nprog} \\
+ \end{nprog} \\
\end{tabular}
\caption{Instance and vtable layout of @|SodObject|}
\label{fig:structures.root.sodobject}
\end{figure}
\begin{describe}[SodObject]{cls}
- {[nick = obj, metaclass = SodClass, lisp_metaclass = sod_class] \\
- class SodObject \{ \\ \ind
+ {[nick = obj, metaclass = SodClass,
+ lisp_metaclass = sod_class] \\
+ class SodObject \{ \\ \ind
void init(?);
\}}
\subsection{The SodClass class} \label{sec:structures.root.sodclass}
\begin{describe}[SodClass]{cls}
- {[nick = cls, link = SodObject] \\
- class SodClass : SodObject \{ \\ \ind
- const char *name; \\
- const char *nick; \\
- size_t initsz; \\
- size_t align; \\
- void *(*imprint)(void *@<p>); \\
- size_t n_supers; \\
- const SodClass *const *supers; \\
- size_t n_cpl; \\
- const SodClass *const *cpl; \\
- const SodClass *link; \\
- const SodClass *head; \\
- size_t level; \\
- size_t n_chains; \\
- const struct sod_chain *chains; \\
- size_t off_islots; \\
- size_t islotsz; \- \\
+ {[nick = cls, link = SodObject] \\
+ class SodClass: SodObject \{ \\ \ind
+ const char *name; \\
+ const char *nick; \\
+ size_t initsz; \\
+ size_t align; \\
+ void *(*imprint)(void *@<p>); \\
+ size_t n_supers; \\
+ const SodClass *const *supers; \\
+ size_t n_cpl; \\
+ const SodClass *const *cpl; \\
+ const SodClass *link; \\
+ const SodClass *head; \\
+ size_t level; \\
+ size_t n_chains; \\
+ const struct sod_chain *chains; \\
+ size_t off_islots; \\
+ size_t islotsz; \-\\
\}}
The @|SodClass| class defines no additional messages , but there are a
\end{describe}
\begin{describe}[struct sod_chain]{type}
- {struct sod_chain \{ \\ \ind
- size_t n_classes; \\
- const SodClass *const *classes; \\
- size_t off_ichain; \\
- const struct sod_vtable *vt; \\
- size_t ichainsz; \- \\
+ {struct sod_chain \{ \\ \ind
+ size_t n_classes; \\
+ const SodClass *const *classes; \\
+ size_t off_ichain; \\
+ const struct sod_vtable *vt; \\
+ size_t ichainsz; \-\\
\};}
The @|struct sod_chain| structure describes an individual chain of
type @|struct $C$__ilayout|.
\begin{prog}
- struct $C$__ilayout \{ \\ \ind
- union $C$__ichainu_$h$ \{ \\ \ind
- struct $C$__ichain_$h$ \{ \\ \ind
- const struct $C$__vt_$h$ *_vt; \\
- struct $H$__islots $h$; \\
- \quad$\vdots$ \\
- struct $C$__islots \{ \\ \ind
- @<type>_1 @<slot>_1; \\
- \quad$\vdots$ \\
- @<type>_n @<slot>_n; \- \\
- \} $c$; \- \\
- \} $c$; \\
- struct $H$__ichain_$h$ $h$; \\
- \quad$\vdots$ \- \\
- \} $h$; \\
- union $B$__ichainu_$i$ $i$; \\
- \quad$\vdots$ \- \\
- \};
- \\+
+ struct $C$__ilayout \{ \\ \ind
+ union $C$__ichainu_$h$ \{ \\ \ind
+ struct $C$__ichain_$h$ \{ \\ \ind
+ const struct $C$__vt_$h$ *_vt; \\
+ struct $H$__islots $h$; \\
+ \quad$\vdots$ \\
+ struct $C$__islots \{ \\ \ind
+ @<type>_1 @<slot>_1; \\
+ \quad$\vdots$ \\
+ @<type>_n @<slot>_n; \-\\
+ \} $c$; \-\\
+ \} $c$; \\
+ struct $A$__ichain_$h$ $a$; \\
+ \quad$\vdots$ \-\\
+ \} $h$; \\
+ union $B$__ichainu_$i$ $i$; \\
+ \quad$\vdots$ \-\\
+ \}; \\+
+
typedef struct $C$__ichain_$h$ $C$;
\end{prog}
naming their least specific classes; the least specific class in a chain is
called the \emph{chain head}. Suppose that the chain head of the chain
containing $C$ itself is named $H$ (though keep in mind that it's possible
-that .$H$ is in fact $C$ itself.)
+that $H$ is in fact $C$ itself.)
\subsubsection{The ilayout structure}
The @|ilayout| structure contains one member for each of $C$'s superclass
struct $A$__ichain_$h$ $a$;
\end{prog}
for each of $C$'s superclasses $A$ in the same chain in some (unimportant)
-order.
+order. The (somewhat obtuse) purpose of this union is to engage the `common
+initial sequence' rule of \cite[6.5.2.3]{FIXME:C99}.
\subsubsection{The ichain structure}
-The
-@|ichain|
-structure contains (in order), a pointer
+The @|ichain| structure contains (in order), a pointer
\begin{prog}
const struct $C$__vt_$h$ *_vt;
\end{prog}
A vtable for a class $C$ with chain head $H$ has the following general
structure.
\begin{prog}
- union $C$__vtu_$h$ \{ \\ \ind
- struct $C$__vt_$h$ \{ \\ \ind
- const $P$ *_class; \\
- size_t _base; \\
- \quad$\vdots$ \\
- const $Q$ *_cls_$j$; \\
- \quad$\vdots$ \\
- ptrdiff_t _off_$i$; \\
- \quad$\vdots$ \\
- struct $C$__vtmsgs_$a$ \{ \\ \ind
- @<type> (*@<msg>)($C$ *, $\dots$); \\
- \quad$\vdots$ \- \\
- \} $a$; \\
- \quad$\vdots$ \- \\
- \} $c$; \- \\
- \};
- \\+
+ union $C$__vtu_$h$ \{ \\ \ind
+ struct $C$__vt_$h$ \{ \\ \ind
+ const $P$ *_class; \\
+ size_t _base; \\
+ \quad$\vdots$ \\
+ const $Q$ *_cls_$j$; \\
+ \quad$\vdots$ \\
+ ptrdiff_t _off_$i$; \\
+ \quad$\vdots$ \\
+ struct $C$__vtmsgs_$a$ \{ \\ \ind
+ @<type> (*@<msg>)($C$ *, $\dots$); \\
+ \quad$\vdots$ \-\\
+ \} $a$; \\
+ \quad$\vdots$ \-\\
+ \} $c$; \-\\
+ \}; \\+
+
extern const union $C$__vtu_$h$ $C$__vtable_$h$;
\end{prog}
+In the following, let $M$ be the metaclass of $C$.
+
\subsubsection{The vtu union}
The outer layer is a @|union $C$__vtu_$h$| containing a member
\begin{prog}
for each of $C$'s superclasses $A$ in the same chain, with $C$ itself listed
first.
-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
+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
\begin{prog}
const union $A$__vtu_$i$ $C$__vtable_$i$;
\end{prog}
\end{prog}
or a standard message which takes keyword arguments, defined as
\begin{prog}
- @<type>_0 $m$(\=@<type>_1 @<arg>_1, $\ldots$, @<type>_n @<arg>_n? \+ \\
- @<type>_{n+1} @<kw>_{n+1} @[= @<dflt>_{n+1}@], $\ldots$,
- @<type>_m @<kw>_m @[= @<dflt>_m@]);
+ @<type>_0 $m$(\=@<type>_1 @<arg>_1,
+ $\ldots$,
+ @<type>_n @<arg>_n? \+\\
+ @<type>_{n+1} @<kw>_{n+1} @[= @<dflt>_{n+1}@],
+ $\ldots$,
+ @<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
list or keywords.
\begin{prog}
@<type>_0 $m$($C$ *me, @<type>_1 @<arg>_1, $\ldots$,
- @<type>_n @<arg>_n, \dots); \\
+ @<type>_n @<arg>_n, \dots); \\
@<type>_0 $m$__v($C$ *me, @<type>_1 @<arg>_1, $\ldots$,
@<type>_n @<arg>_n, va_list sod__ap);
\end{prog}
Finally, the class object is defined as
\begin{prog}
- extern const struct $R$__ilayout $C$__classobj; \\
+ extern const struct $R$__ilayout $C$__classobj; \\
\#define $C$__class (\&$C$__classobj.$j$.$r$)
\end{prog}
The exported symbol @|$C$__classobj| contains the entire class instance.
~mdw / sod / blobdiff