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bpo-46417: Add _PyType_GetSubclasses() function (GH-30761)

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Add a new _PyType_GetSubclasses() function to get type's subclasses.

_PyType_GetSubclasses(type) returns a list which holds strong
refererences to subclasses. It is safer than iterating on
type->tp_subclasses which yields weak references and can be modified
in the loop.

_PyType_GetSubclasses(type) now holds a reference to the tp_subclasses
dict while creating the list of subclasses.

set_collection_flag_recursive() of _abc.c now uses
_PyType_GetSubclasses().
This commit is contained in:
Victor Stinner 2022-01-21 23:29:10 +01:00 • committed by GitHub
parent 57d1855682
commit 8ee07dda13
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3 changed files with 75 additions and 54 deletions
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18
Modules/_abc.c
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@ -4,6 +4,7 @@
#endif
#include "Python.h"
#include "pycore_object.h" // _PyType_GetSubclasses()
#include "pycore_moduleobject.h" // _PyModule_GetState()
#include "clinic/_abc.c.h"
@ -493,21 +494,20 @@ set_collection_flag_recursive(PyTypeObject *child, unsigned long flag)
{
return;
}
child->tp_flags &= ~COLLECTION_FLAGS;
child->tp_flags |= flag;
PyObject *grandchildren = child->tp_subclasses;
PyObject *grandchildren = _PyType_GetSubclasses(child);
if (grandchildren == NULL) {
return;
}
assert(PyDict_CheckExact(grandchildren));
Py_ssize_t i = 0;
while (PyDict_Next(grandchildren, &i, NULL, &grandchildren)) {
assert(PyWeakref_CheckRef(grandchildren));
PyObject *grandchild = PyWeakref_GET_OBJECT(grandchildren);
if (PyType_Check(grandchild)) {
set_collection_flag_recursive((PyTypeObject *)grandchild, flag);
}
for (Py_ssize_t i = 0; i < PyList_GET_SIZE(grandchildren); i++) {
PyObject *grandchild = PyList_GET_ITEM(grandchildren, i);
set_collection_flag_recursive((PyTypeObject *)grandchild, flag);
}
Py_DECREF(grandchildren);
}
/*[clinic input]