final patches from Neil Schemenauer for garbage collection
diff --git a/Include/objimpl.h b/Include/objimpl.h
index 860030f..003dfdf 100644
--- a/Include/objimpl.h
+++ b/Include/objimpl.h
@@ -203,7 +203,6 @@
( (type *) PyObject_InitVar( \
(PyVarObject *) PyObject_MALLOC( _PyObject_VAR_SIZE((typeobj),(n)) ),\
(typeobj), (n)) )
-#define PyObject_DEL(op) PyObject_FREE(op)
/* This example code implements an object constructor with a custom
allocator, where PyObject_New is inlined, and shows the important
@@ -234,11 +233,67 @@
the 1st step is performed automatically for you, so in a C++ class
constructor you would start directly with PyObject_Init/InitVar. */
+/*
+ * Garbage Collection Support
+ * ==========================
+ */
+/* To make a new object participate in garbage collection use
+ PyObject_{New, VarNew, Del} to manage the memory. Set the type flag
+ Py_TPFLAGS_GC and define the type method tp_recurse. You should also
+ add the method tp_clear if your object is mutable. Include
+ PyGC_INFO_SIZE in the calculation of tp_basicsize. Call
+ PyObject_GC_Init after the pointers followed by tp_recurse become
+ valid (usually just before returning the object from the allocation
+ method. Call PyObject_GC_Fini before those pointers become invalid
+ (usually at the top of the deallocation method). */
#ifndef WITH_CYCLE_GC
-#define PyGC_INFO_SIZE 0
-#endif
+
+#define PyGC_HEAD_SIZE 0
+#define PyObject_GC_Init(op)
+#define PyObject_GC_Fini(op)
+#define PyObject_AS_GC(op) (op)
+#define PyObject_FROM_GC(op) (op)
+#define PyObject_DEL(op) PyObject_FREE(op)
+
+#else
+
+/* Add the object into the container set */
+extern DL_IMPORT(void) _PyGC_Insert Py_PROTO((PyObject *));
+
+/* Remove the object from the container set */
+extern DL_IMPORT(void) _PyGC_Remove Py_PROTO((PyObject *));
+
+#define PyObject_GC_Init(op) _PyGC_Insert((PyObject *)op)
+#define PyObject_GC_Fini(op) _PyGC_Remove((PyObject *)op)
+
+/* Structure *prefixed* to container objects participating in GC */
+typedef struct _gc_head {
+ struct _gc_head *gc_next;
+ struct _gc_head *gc_prev;
+ int gc_refs;
+} PyGC_Head;
+
+#define PyGC_HEAD_SIZE sizeof(PyGC_Head)
+
+/* Test if a type has a GC head */
+#define PyType_IS_GC(t) PyType_HasFeature((t), Py_TPFLAGS_GC)
+
+/* Test if an object has a GC head */
+#define PyObject_IS_GC(o) PyType_IS_GC((o)->ob_type)
+
+/* Get an object's GC head */
+#define PyObject_AS_GC(o) ((PyGC_Head *)(o)-1)
+
+/* Get the object given the PyGC_Head */
+#define PyObject_FROM_GC(g) ((PyObject *)(((PyGC_Head *)g)+1))
+
+#define PyObject_DEL(op) PyObject_FREE( PyObject_IS_GC(op) ? \
+ (ANY *)PyObject_AS_GC(op) : \
+ (ANY *)(op) )
+
+#endif /* WITH_CYCLE_GC */
#ifdef __cplusplus
}