size_t _base; \\
struct SodObject__vtmsgs_obj \{ \\ \ind
void (*init)(SodObject *me, ...); \\
- void (*init__v)(SodObject *me, va_list); \- \\
+ void (*init__v)(SodObject *me, va_list); \\
+ int (*teardown)(SodObject *me); \- \\
\} obj; \- \\
\};
\end{nprog} \\
The instance and vtable layout of @|SodObject| is shown in
\xref{fig:structures.root.sodobject}.
- The following message is defined.
+ The following messages are defined.
\begin{describe}[obj.init]{msg}{void init(?);}
Initialize a newly allocated instance.
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.
+ defined slot initializers, and execute the initialization fragments.
+ Each slot is initialized using the most specific applicable initializer,
+ if any. Slots without an initializer are left uninitialized.
+
+ Slots are initialized and initialization fragments executed together, a
+ superclass at a time: first, the superclass's slots are initialized (if
+ any); then the superclass's initialization fragments (if any) are
+ executed, starting with the least specific superclass first. Slots and
+ initialization fragments defined by the same class are processed in the
+ order in which they appear in the class definition.
There are no standard keyword arguments; methods on subclasses are free
to introduce their own in the usual way.
For more details on instance construction, see
\xref{sec:concepts.lifecycle.birth}.
\end{describe}
+
+ \begin{describe}[obj.teardown]{msg}{int teardown();}
+ Teardown an instance which is no longer required.
+
+ The message returns an integer flag. A zero value means that the
+ instance is safe to deallocate. A nonzero value means that the instance
+ should not be deallocated, and that it is safe for the caller to simply
+ forget about it. This simple protocol may be used, for example, to
+ implement a reference-counting system.
+
+ This message uses a custom method combination which works like the
+ standard method combination except that default behaviour is invoked if
+ no primary or around method overrides.
+
+ This default behaviour is to execute each superclass's teardown
+ fragments, most specific first, and then return zero to indicate that the
+ object is ready for deallocation. Teardown fragments defined by the same
+ class are processed in the order in which they appear in the class
+ definition.
+
+ It is usual to provide complex teardown behaviour as @|before| methods.
+ Logic to decide whether to allow deallocation is usually implemented as
+ @|around| methods.
+ \end{describe}
\end{describe}
const char *name; \\
const char *nick; \\
size_t initsz; \\
+ size_t align; \\
void *(*imprint)(void *@<p>); \\
size_t n_supers; \\
const SodClass *const *supers; \\
\item[initsz] The size in bytes required to store an instance of the class.
+ \item[align] A sufficient alignment for the class's instance storage.
+
\item[imprint] A pointer to a function: given a pointer @<p> to at least
@<initsz> bytes of appropriately aligned memory, `imprint' this memory it
so that it becomes a minimally functional instance of the class: all of
~mdw / sod / blobdiff