The concrete types described in \xref{sec:structures.common} and
\ref{sec:structures.root} are declared by the header file @|<sod/sod.h>|.
-The definitions described in sections \ref{sec:structures.layout} are defined
-in the header file generated by the containing module.
+The definitions described in \xref{sec:structures.layout} are defined in the
+header file generated by the containing module.
%%%--------------------------------------------------------------------------
\section{Common instance structure} \label{sec:structures.common}
\begin{figure}[tbp]
\begin{tabular}{p{10pt}p{10pt}}
- \begin{prog}
+ \begin{nprog}
struct SodObject__ilayout \{ \\ \ind
union \{ \\ \ind
struct SodObject__ichain_obj \{ \\ \ind
\} obj; \- \\
\} obj; \- \\
\};
- \end{prog}
+ \end{nprog}
&
- \begin{prog}
+ \begin{nprog}
struct SodObject__vt_obj \{ \\ \ind
const SodClass *_class; \\
- size_t _base; \- \\
+ size_t _base; \\
+ struct SodObject__vtmsgs_obj \{ \\ \ind
+ void (*init)(SodObject *me, ...); \\
+ void (*init__v)(SodObject *me, va_list); \- \\
+ \} obj; \- \\
\};
- \end{prog} \\
+ \end{nprog} \\
\end{tabular}
\caption{Instance and vtable layout of @|SodObject|}
\label{fig:structures.root.sodobject}
\begin{describe}[SodObject]{cls}
{[nick = obj, metaclass = SodClass, lisp_metaclass = sod_class] \\
- class SodObject \{ \}}
+ class SodObject \{ \\ \ind
+ void init(?);
+ \}}
- The @|SodObject| class defines no slots or messages. Because @|SodObject|
- has no direct superclasses, there is only one chain, and no inherited
- slots or messages, so the single chain contains only a vtable pointer.
+ The @|SodObject| class defines no slots. Because @|SodObject| has no
+ direct superclasses, there is only one chain, and no inherited slots or
+ messages, so the single chain contains only a vtable pointer.
- Since there are no messages, and @|SodClass| also has only one chain, the
- vtable contains only the standard class pointer and offset-to-base members.
- In a direct instance of @|SodObject| (why would you want one?) the class
- pointer contains the address of @|SodObject__class| and the offset is zero.
+ Since @|SodClass| also has only one chain, the vtable contains only the
+ standard class pointer and offset-to-base members. In a direct instance of
+ @|SodObject| (why would you want one?) the class pointer contains the
+ address of @|SodObject__class| and the offset is zero.
The instance and vtable layout of @|SodObject| is shown in
\xref{fig:structures.root.sodobject}.
+
+ The following message is defined.
+
+ \begin{describe}[obj.init]{msg}{void init(?);}
+ Initialize a newly allocated instance.
+
+ This message uses a custom method combination which works like the
+ standard method combination except that default behaviour specific to the
+ receiver's direct class is invoked if no primary or around method
+ overrides. This default behaviour may be invoked multiple times if some
+ method calls on its @|next_method| function more than once.
+
+ This default behaviour is to initialize the instance's slots using the
+ defined slot initializers: each slot is initialized using the most
+ specific applicable initializer, if any. Slots without an initializer
+ are left uninitialized.
+
+ There are no standard keyword arguments; methods on subclasses are free
+ to introduce their own in the usual way.
+
+ It is usual to provide complex initialization behaviour as @|after|
+ methods. This ensures that slots have been initialized as necessary
+ before the method executes.
+
+ For more details on instance construction, see
+ \xref{sec:concepts.lifecycle.birth}.
+ \end{describe}
\end{describe}
const char *nick; \\
size_t initsz; \\
void *(*imprint)(void *@<p>); \\
- void *(*init)(void *@<p>); \\
size_t n_supers; \\
const SodClass *const *supers; \\
size_t n_cpl; \\
size_t islotsz; \- \\
\}}
- The @|SodClass| class defines no messages, but there are a number of slots.
- Its only direct superclass is @|SodObject| and so (like its superclass) its
- vtable is trivial.
+ The @|SodClass| class defines no additional messages , but there are a
+ number of slots. Its only direct superclass is @|SodObject| and so (like
+ its superclass) its vtable is simple.
The slots defined are as follows.
\begin{description} \let\makelabel\code
the vtable and class pointers are properly initialized, but the slots are
left untouched. The function returns its argument @<p>.
- \item[init] A pointer to a function: given a pointer @<p> to at least
- @<initsz> bytes of appropriately aligned memory, initialize an instance
- of the class in it: all of the vtable and class pointers are initialized,
- as are slots for which initializers are defined. Other slots are left
- untouched. The function returns its argument @<p>.
-
\item[n_supers] The number of direct superclasses. (This is zero exactly
in the case of @|SodObject|.)
union $B$__ichainu_$i$ $i$; \\
\quad$\vdots$ \- \\
\};
- \\[\bigskipamount]
+ \\+
typedef struct $C$__ichain_$h$ $C$;
\end{prog}
\quad$\vdots$ \- \\
\} $c$; \- \\
\};
- \\[\bigskipamount]
+ \\+
extern const union $C$__vtu_$h$ $C$__vtable_$h$;
\end{prog}
\begin{prog}
@<type>_0 $m$(@<type>_1 @<arg>_1, $\ldots$, @<type>_n @<arg>_n, \dots);
\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@]);
+\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
argument of type @|va_list| in place of the variable portion of the argument
-list.
+list or keywords.
\begin{prog}
@<type>_0 $m$($C$ *me, @<type>_1 @<arg>_1, $\ldots$,
@<type>_n @<arg>_n, \dots); \\
which makes sending the message $m$ to an instance of (any subclass of) $C$
somewhat less ugly.
-If $m$ takes a variable number of arguments, the macro is more complicated
-and is only available in compilers advertising C99 support, but the effect is
-the same. For each variable-argument message, there is also an additional
-macro for calling the `valist' entry point.
+If $m$ takes a variable number of arguments, or keyword arguments, the macro
+is more complicated and is only available in compilers advertising C99
+support, but the effect is the same. For each variable-argument message,
+there is also an additional macro for calling the `valist' entry point.
\begin{prog}
\#define $C$_$m$__v(@<me>, $\ldots$, @<sod__ap>)
@<me>@->_vt@->$c$.$m$__v(@<me>, $\ldots$, @<sod__ap>)
~mdw / sod / blobdiff