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Use weakrefs

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This commit is contained in:
Xuehai Pan
2026-01-23 03:00:40 +08:00
parent b147430e46
commit 05576f11a7
2 changed files with 30 additions and 14 deletions
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20
include/pybind11/detail/class.h
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@@ -11,10 +11,16 @@
#include <pybind11/attr.h>
#include <pybind11/options.h>
#include <pybind11/pybind11.h>
#include <pybind11/pytypes.h>
#include "exception_translation.h"
PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
class weakref;
class cpp_function;
PYBIND11_NAMESPACE_BEGIN(detail)
#if !defined(PYPY_VERSION)
@@ -252,11 +258,6 @@ extern "C" inline void pybind11_meta_dealloc(PyObject *obj) {
});
PyType_Type.tp_dealloc(obj);
// Release the references to the internals capsules that were acquired in make_new_python_type.
// See the comment there for details on preventing use-after-free during interpreter shutdown.
Py_XDECREF(get_internals_capsule());
Py_XDECREF(get_local_internals_capsule());
}
/** This metaclass is assigned by default to all pybind11 types and is required in order
@@ -834,15 +835,6 @@ inline PyObject *make_new_python_type(const type_record &rec) {
PYBIND11_SET_OLDPY_QUALNAME(type, qualname);
// Prevent use-after-free during interpreter shutdown. GC order is not guaranteed, so the
// internals capsule may be destroyed (resetting internals via internals_shutdown) before all
// pybind11 types are destroyed. If a type's tp_traverse/tp_clear then calls py::cast, it
// would recreate an empty internals and fail because the type registry is gone. By holding
// references to the capsules, we ensure they outlive all pybind11 types. The decref happens
// in pybind11_meta_dealloc.
Py_XINCREF(get_internals_capsule());
Py_XINCREF(get_local_internals_capsule());
return reinterpret_cast<PyObject *>(type);
}

24
include/pybind11/pybind11.h
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@@ -1692,6 +1692,30 @@ protected:
m_ptr = make_new_python_type(rec);
// Prevent use-after-free during interpreter shutdown. GC order is not guaranteed, so the
// internals capsule may be destroyed (resetting internals via internals_shutdown) before
// all pybind11 types are destroyed. If a type's tp_traverse/tp_clear then calls py::cast,
// it would recreate an empty internals and fail because the type registry is gone. By
// holding references to the capsules, we ensure they outlive all pybind11 types.
// We use weakrefs on the type with a cpp_function callback. When the type is destroyed,
// Python will call the callback which releases the capsule reference and the weakref.
if (PyObject *capsule = get_internals_capsule()) {
Py_INCREF(capsule);
(void) weakref(handle(m_ptr), cpp_function([](handle prevent_release) -> void {
Py_XDECREF(get_internals_capsule());
prevent_release.dec_ref();
}))
.release();
}
if (PyObject *capsule = get_local_internals_capsule()) {
Py_INCREF(capsule);
(void) weakref(handle(m_ptr), cpp_function([](handle prevent_release) -> void {
Py_XDECREF(get_local_internals_capsule());
prevent_release.dec_ref();
}))
.release();
}
/* Register supplemental type information in C++ dict */
auto *tinfo = new detail::type_info();
tinfo->type = reinterpret_cast<PyTypeObject *>(m_ptr);