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GDB is currently using the Python unlimited API. Migrating the codebase to the Python limited API would have for benefit to make a GDB build artifacts compatible with older and newer versions of Python that they were built with. This patch prepares the ground for migrating the existing C extension types from static types to heap-allocated ones, by removing the dependency on tp_dictoffset, which is unavailable when using the limited API. One of the most common incompatibilities in the current static type declarations is the tp_dictoffset slot, which specifies the dictionary offset within the instance structure. Historically, the unlimited API has provided two approaches to supply a dictionary for __dict__: * A managed dictionary. Setting Py_TPFLAGS_MANAGED_DICT in tp_flags indicates that the instances of the type have a __dict__ attribute, and that the dictionary is managed by Python. According to the Python documentation, this is the recommended approach. However, this flag was introduced in 3.12, together with PyObject_VisitManagedDict() and PyObject_ClearManagedDict(), neither of which is part of the limited API (at least for now). As a result, this recommended approach is not viable in the context of the limited API. * An instance dictionary, for which the offset in the instance is provided via tp_dictoffset. According to the Python documentation, this "tp slot" is on the deprecation path, and Py_TPFLAGS_MANAGED_DICT should be used instead. Given the age of the GDB codebase and the requirement to support older Python versions (>= 3.4), no need to argue that today, the implementation of __dict__ relies on tp_dictoffset. However, in the context of the limited API, PyType_Slot does not provide a Py_tp_dictoffset member, so another approach is needed to provide __dict__ to instances of C extension types. Given the constraints of the limited API, the proposed solution consists in providing a dictionary through a common base class, gdbpy__dict__wrapper. This helper class owns a dictionary member corresponding to __dict__, and any C extension type requiring a __dict__ must inherit from it. Since extension object must also be convertible to PyObject, this wrapper class publicly inherits from PyObject as well. Access to the dictionary is provided via a custom getter defined in a PyGetSetDef, similarily to what was previously done with gdb_py_generic_dict(). Because __dict__ participates in attribute look-up, and since this dictionary is neither managed by Python nor exposed via tp_dictoffset, custom implementations of tp_getattro and tp_setattro are required to correctly redirect attribute look-ups to the dictionary. These custom implementations — equivalent to PyObject_GenericGetAttr() and PyObject_GenericSetAttr() — must be installed via tp_getattro / tp_setattro for static types, or Py_tp_getattro / Py_tp_setattro for heap-allocated types. - gdbpy__dict__wrapper: a base class for C extension objects that own a __dict__. - gdb_py_generic_dict_getter: a __dict__ getter for extension types derived from gdbpy__dict__wrapper. - gdb_py_generic_getattro: equivalent of PyObject_GenericGetAttr, but fixes the look-up of __dict__. - gdb_py_generic_setattro: equivalent of PyObject_GenericSetAttr, but fixes the look-up of __dict__. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=23830 Approved-By: Tom Tromey <tom@tromey.com>
148 lines
5.1 KiB
C
148 lines
5.1 KiB
C
/* Python interface to inferior events.
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Copyright (C) 2009-2026 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "py-event.h"
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void
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evpy_dealloc (PyObject *self)
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{
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Py_XDECREF (((event_object *) self)->dict);
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Py_TYPE (self)->tp_free (self);
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}
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gdbpy_ref<>
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create_event_object (PyTypeObject *py_type)
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{
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gdbpy_ref<event_object> event_obj (PyObject_New (event_object, py_type));
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if (event_obj == NULL)
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return NULL;
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event_obj->dict = PyDict_New ();
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if (!event_obj->dict)
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return NULL;
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return gdbpy_ref<> ((PyObject *) event_obj.release ());
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}
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/* Add the attribute ATTR to the event object EVENT. In
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python this attribute will be accessible by the name NAME.
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returns 0 if the operation succeeds and -1 otherwise. This
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function acquires a new reference to ATTR. */
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int
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evpy_add_attribute (PyObject *event, const char *name, PyObject *attr)
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{
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return PyObject_SetAttrString (event, name, attr);
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}
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/* Initialize the Python event code. */
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static int
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gdbpy_initialize_event ()
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{
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return gdbpy_type_ready (&event_object_type);
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}
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/* Notify the list of listens that the given EVENT has occurred.
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returns 0 if emit is successful -1 otherwise. */
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int
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evpy_emit_event (PyObject *event,
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eventregistry_object *registry)
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{
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Py_ssize_t i;
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/* Create a copy of call back list and use that for
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notifying listeners to avoid skipping callbacks
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in the case of a callback being disconnected during
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a notification. */
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gdbpy_ref<> callback_list_copy (PySequence_List (registry->callbacks));
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if (callback_list_copy == NULL)
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return -1;
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for (i = 0; i < PyList_Size (callback_list_copy.get ()); i++)
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{
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PyObject *func = PyList_GetItem (callback_list_copy.get (), i);
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if (func == NULL)
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return -1;
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gdbpy_ref<> func_result (PyObject_CallFunctionObjArgs (func, event,
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NULL));
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if (func_result == NULL)
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{
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/* Print the trace here, but keep going -- we want to try to
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call all of the callbacks even if one is broken. */
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gdbpy_print_stack ();
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}
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}
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return 0;
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}
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GDBPY_INITIALIZE_FILE (gdbpy_initialize_event);
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static gdb_PyGetSetDef event_object_getset[] =
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{
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{ "__dict__", gdb_py_generic_dict_getter, NULL,
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"The __dict__ for this event.", NULL },
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{ NULL }
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};
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PyTypeObject event_object_type =
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{
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PyVarObject_HEAD_INIT (NULL, 0)
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"gdb.Event", /* tp_name */
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sizeof (event_object), /* tp_basicsize */
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0, /* tp_itemsize */
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evpy_dealloc, /* tp_dealloc */
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0, /* tp_print */
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0, /* tp_getattr */
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0, /* tp_setattr */
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0, /* tp_compare */
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0, /* tp_repr */
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0, /* tp_as_number */
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0, /* tp_as_sequence */
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0, /* tp_as_mapping */
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0, /* tp_hash */
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0, /* tp_call */
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0, /* tp_str */
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gdb_py_generic_getattro, /* tp_getattro */
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gdb_py_generic_setattro, /* tp_setattro */
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0, /* tp_as_buffer */
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /* tp_flags */
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"GDB event object", /* tp_doc */
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0, /* tp_traverse */
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0, /* tp_clear */
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0, /* tp_richcompare */
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0, /* tp_weaklistoffset */
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0, /* tp_iter */
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0, /* tp_iternext */
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0, /* tp_methods */
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0, /* tp_members */
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event_object_getset, /* tp_getset */
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0, /* tp_base */
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0, /* tp_dict */
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0, /* tp_descr_get */
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0, /* tp_descr_set */
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0, /* tp_dictoffset */
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0, /* tp_init */
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0 /* tp_alloc */
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};
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