[Python-Dev] reference leaks, del, and annotations

Mon Apr 3 21:49:58 CEST 2006

On Apr 3, 2006, at 3:12 PM, Neil Schemenauer wrote:
> Guido van Rossum <guido at python.org> wrote:
>> This would require a bit "__del__ already called" on an object,
>> but don't we have a whole word of GC-related flags?
>> No.

Actually there is. Kinda. Currently python's refcounting scheme uses 
4 words per object (gc_next, gc_prev, gc_refs, ob_refcnt), and has 
one spare word in the padding of PyGC_Head that's just sitting there 
wasting memory. So really it's using up 5 words per object, and that 
5th word could actually be used for flags...
/* GC information is stored BEFORE the object structure. */
typedef union _gc_head {
 struct {
 union _gc_head *gc_next;
 union _gc_head *gc_prev;
 int gc_refs;
 } gc;
 long double dummy; /* force worst-case alignment */
} PyGC_Head;
#define PyObject_HEAD \
 _PyObject_HEAD_EXTRA \
 int ob_refcnt; \
 struct _typeobject *ob_type;
typedef struct _object {
 PyObject_HEAD
} PyObject;
James

[Python-Dev] reference leaks, __del__, and annotations

[Python-Dev] reference leaks, del, and annotations