Add _Py_AS_GC macro. It will be used by the trashcan code on object.c.
diff --git a/Include/objimpl.h b/Include/objimpl.h
index e27de30..50ea51c 100644
--- a/Include/objimpl.h
+++ b/Include/objimpl.h
@@ -235,10 +235,12 @@
extern PyGC_Head _PyGC_generation0;
+#define _Py_AS_GC(o) ((PyGC_Head *)(o)-1)
+
/* Tell the GC to track this object. NB: While the object is tracked the
* collector it must be safe to call the ob_traverse method. */
#define _PyObject_GC_TRACK(o) do { \
- PyGC_Head *g = (PyGC_Head *)(o)-1; \
+ PyGC_Head *g = _Py_AS_GC(o); \
if (g->gc.gc_next != NULL) \
Py_FatalError("GC object already in linked list"); \
g->gc.gc_next = &_PyGC_generation0; \
@@ -249,7 +251,7 @@
/* Tell the GC to stop tracking this object. */
#define _PyObject_GC_UNTRACK(o) do { \
- PyGC_Head *g = (PyGC_Head *)(o)-1; \
+ PyGC_Head *g = _Py_AS_GC(o); \
g->gc.gc_prev->gc.gc_next = g->gc.gc_next; \
g->gc.gc_next->gc.gc_prev = g->gc.gc_prev; \
g->gc.gc_next = NULL; \