diff options
| -rw-r--r-- | Include/internal/pycore_object.h | 33 | ||||
| -rw-r--r-- | Modules/gcmodule.c | 9 | ||||
| -rw-r--r-- | Objects/typeobject.c | 12 |
3 files changed, 47 insertions, 7 deletions
diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h index 173d367..b3b0b84 100644 --- a/Include/internal/pycore_object.h +++ b/Include/internal/pycore_object.h @@ -217,6 +217,16 @@ extern void _Py_PrintReferences(FILE *); extern void _Py_PrintReferenceAddresses(FILE *); #endif + +/* Return the *address* of the object's weaklist. The address may be + * dereferenced to get the current head of the weaklist. This is useful + * for iterating over the linked list of weakrefs, especially when the + * list is being modified externally (e.g. refs getting removed). + * + * The returned pointer should not be used to change the head of the list + * nor should it be used to add, remove, or swap any refs in the list. + * That is the sole responsibility of the code in weakrefobject.c. + */ static inline PyObject ** _PyObject_GET_WEAKREFS_LISTPTR(PyObject *op) { @@ -226,10 +236,33 @@ _PyObject_GET_WEAKREFS_LISTPTR(PyObject *op) (PyTypeObject *)op); return _PyStaticType_GET_WEAKREFS_LISTPTR(state); } + // Essentially _PyObject_GET_WEAKREFS_LISTPTR_FROM_OFFSET(): Py_ssize_t offset = Py_TYPE(op)->tp_weaklistoffset; return (PyObject **)((char *)op + offset); } +/* This is a special case of _PyObject_GET_WEAKREFS_LISTPTR(). + * Only the most fundamental lookup path is used. + * Consequently, static types should not be used. + * + * For static builtin types the returned pointer will always point + * to a NULL tp_weaklist. This is fine for any deallocation cases, + * since static types are never deallocated and static builtin types + * are only finalized at the end of runtime finalization. + * + * If the weaklist for static types is actually needed then use + * _PyObject_GET_WEAKREFS_LISTPTR(). + */ +static inline PyWeakReference ** +_PyObject_GET_WEAKREFS_LISTPTR_FROM_OFFSET(PyObject *op) +{ + assert(!PyType_Check(op) || + ((PyTypeObject *)op)->tp_flags & Py_TPFLAGS_HEAPTYPE); + Py_ssize_t offset = Py_TYPE(op)->tp_weaklistoffset; + return (PyWeakReference **)((char *)op + offset); +} + + // Fast inlined version of PyObject_IS_GC() static inline int _PyObject_IS_GC(PyObject *obj) diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c index dcd46fe..97cb6e6 100644 --- a/Modules/gcmodule.c +++ b/Modules/gcmodule.c @@ -794,9 +794,12 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old) if (! _PyType_SUPPORTS_WEAKREFS(Py_TYPE(op))) continue; - /* It supports weakrefs. Does it have any? */ - wrlist = (PyWeakReference **) - _PyObject_GET_WEAKREFS_LISTPTR(op); + /* It supports weakrefs. Does it have any? + * + * This is never triggered for static types so we can avoid the + * (slightly) more costly _PyObject_GET_WEAKREFS_LISTPTR(). + */ + wrlist = _PyObject_GET_WEAKREFS_LISTPTR_FROM_OFFSET(op); /* `op` may have some weakrefs. March over the list, clear * all the weakrefs, and move the weakrefs with callbacks diff --git a/Objects/typeobject.c b/Objects/typeobject.c index 1c3f8a9..1f56a58 100644 --- a/Objects/typeobject.c +++ b/Objects/typeobject.c @@ -1505,11 +1505,15 @@ subtype_dealloc(PyObject *self) finalizers since they might rely on part of the object being finalized that has already been destroyed. */ if (type->tp_weaklistoffset && !base->tp_weaklistoffset) { - /* Modeled after GET_WEAKREFS_LISTPTR() */ - PyWeakReference **list = (PyWeakReference **) \ - _PyObject_GET_WEAKREFS_LISTPTR(self); - while (*list) + /* Modeled after GET_WEAKREFS_LISTPTR(). + + This is never triggered for static types so we can avoid the + (slightly) more costly _PyObject_GET_WEAKREFS_LISTPTR(). */ + PyWeakReference **list = \ + _PyObject_GET_WEAKREFS_LISTPTR_FROM_OFFSET(self); + while (*list) { _PyWeakref_ClearRef(*list); + } } } |