[Python-Dev] reference leaks, del, and annotations (original) (raw)

James Y Knight foom at fuhm.net
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

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