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#ifndef Py_INTERNAL_WEAKREF_H
#define Py_INTERNAL_WEAKREF_H
#ifdef __cplusplus
extern "C" {
#endif
#ifndef Py_BUILD_CORE
# error "this header requires Py_BUILD_CORE define"
#endif
#include "pycore_critical_section.h" // Py_BEGIN_CRITICAL_SECTION()
#include "pycore_lock.h"
#include "pycore_object.h" // _Py_REF_IS_MERGED()
#include "pycore_pyatomic_ft_wrappers.h"
#ifdef Py_GIL_DISABLED
#define WEAKREF_LIST_LOCK(obj) \
_PyInterpreterState_GET() \
->weakref_locks[((uintptr_t)obj) % NUM_WEAKREF_LIST_LOCKS]
// Lock using the referenced object
#define LOCK_WEAKREFS(obj) \
PyMutex_LockFlags(&WEAKREF_LIST_LOCK(obj), _Py_LOCK_DONT_DETACH)
#define UNLOCK_WEAKREFS(obj) PyMutex_Unlock(&WEAKREF_LIST_LOCK(obj))
// Lock using a weakref
#define LOCK_WEAKREFS_FOR_WR(wr) \
PyMutex_LockFlags(wr->weakrefs_lock, _Py_LOCK_DONT_DETACH)
#define UNLOCK_WEAKREFS_FOR_WR(wr) PyMutex_Unlock(wr->weakrefs_lock)
#define FT_CLEAR_WEAKREFS(obj, weakref_list) \
do { \
assert(Py_REFCNT(obj) == 0); \
PyObject_ClearWeakRefs(obj); \
} while (0)
#else
#define LOCK_WEAKREFS(obj)
#define UNLOCK_WEAKREFS(obj)
#define LOCK_WEAKREFS_FOR_WR(wr)
#define UNLOCK_WEAKREFS_FOR_WR(wr)
#define FT_CLEAR_WEAKREFS(obj, weakref_list) \
do { \
assert(Py_REFCNT(obj) == 0); \
if (weakref_list != NULL) { \
PyObject_ClearWeakRefs(obj); \
} \
} while (0)
#endif
static inline int _is_dead(PyObject *obj)
{
// Explanation for the Py_REFCNT() check: when a weakref's target is part
// of a long chain of deallocations which triggers the trashcan mechanism,
// clearing the weakrefs can be delayed long after the target's refcount
// has dropped to zero. In the meantime, code accessing the weakref will
// be able to "see" the target object even though it is supposed to be
// unreachable. See issue gh-60806.
#if defined(Py_GIL_DISABLED)
Py_ssize_t shared = _Py_atomic_load_ssize_relaxed(&obj->ob_ref_shared);
return shared == _Py_REF_SHARED(0, _Py_REF_MERGED);
#else
return (Py_REFCNT(obj) == 0);
#endif
}
static inline PyObject* _PyWeakref_GET_REF(PyObject *ref_obj)
{
assert(PyWeakref_Check(ref_obj));
PyWeakReference *ref = _Py_CAST(PyWeakReference*, ref_obj);
PyObject *obj = FT_ATOMIC_LOAD_PTR(ref->wr_object);
if (obj == Py_None) {
// clear_weakref() was called
return NULL;
}
LOCK_WEAKREFS(obj);
#ifdef Py_GIL_DISABLED
if (ref->wr_object == Py_None) {
// clear_weakref() was called
UNLOCK_WEAKREFS(obj);
return NULL;
}
#endif
if (_Py_TryIncref(obj)) {
UNLOCK_WEAKREFS(obj);
return obj;
}
UNLOCK_WEAKREFS(obj);
return NULL;
}
static inline int _PyWeakref_IS_DEAD(PyObject *ref_obj)
{
assert(PyWeakref_Check(ref_obj));
int ret = 0;
PyWeakReference *ref = _Py_CAST(PyWeakReference*, ref_obj);
PyObject *obj = FT_ATOMIC_LOAD_PTR(ref->wr_object);
if (obj == Py_None) {
// clear_weakref() was called
ret = 1;
}
else {
LOCK_WEAKREFS(obj);
// See _PyWeakref_GET_REF() for the rationale of this test
#ifdef Py_GIL_DISABLED
ret = (ref->wr_object == Py_None) || _is_dead(obj);
#else
ret = _is_dead(obj);
#endif
UNLOCK_WEAKREFS(obj);
}
return ret;
}
extern Py_ssize_t _PyWeakref_GetWeakrefCount(PyObject *obj);
// Clear all the weak references to obj but leave their callbacks uncalled and
// intact.
extern void _PyWeakref_ClearWeakRefsNoCallbacks(PyObject *obj);
PyAPI_FUNC(int) _PyWeakref_IsDead(PyObject *weakref);
#ifdef __cplusplus
}
#endif
#endif /* !Py_INTERNAL_WEAKREF_H */
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