STINNER Victor <[email protected]> added the comment:
At commit ac46eb4ad6662cf6d771b20d8963658b2186c48c ("bpo-38113: Update the
Python-ast.c generator to PEP384 (gh-15957)"):
---------------
static struct PyModuleDef _astmodule = {
PyModuleDef_HEAD_INIT,
"_ast",
NULL,
sizeof(astmodulestate),
NULL,
NULL,
astmodule_traverse,
astmodule_clear,
astmodule_free,
};
#define astmodulestate_global ((astmodulestate
*)PyModule_GetState(PyState_FindModule(&_astmodule)))
PyMODINIT_FUNC
PyInit__ast(void)
{
PyObject *m;
if (!init_types()) return NULL;
m = PyState_FindModule(&_astmodule);
...
return m;
}
---------------
=> I investigated bpo-41194 crash again. It seems like the root issue is more
than PyInit__ast() returns a *borrowed* reference, rather than a strong
reference.
=> The _ast module can only be loaded once, astmodule_free() and
astmodule_clear() are not called at Python exit.
At commit 91e1bc18bd467a13bceb62e16fbc435b33381c82 ("bpo-41194: The _ast module
cannot be loaded more than once (GH-21290)"):
---------------
static astmodulestate global_ast_state;
static astmodulestate *
get_ast_state(PyObject *Py_UNUSED(module))
{
return &global_ast_state;
}
#define get_global_ast_state() (&global_ast_state)
static struct PyModuleDef _astmodule = {
PyModuleDef_HEAD_INIT,
.m_name = "_ast",
.m_size = -1,
.m_traverse = astmodule_traverse,
.m_clear = astmodule_clear,
.m_free = astmodule_free,
};
PyMODINIT_FUNC
PyInit__ast(void)
{
PyObject *m = PyModule_Create(&_astmodule);
if (!m) {
return NULL;
}
astmodulestate *state = get_ast_state(m);
...
}
---------------
* bpo-41194 => ok, PyInit__ast() is fine
* bpo-41631 => ok: PyAST_Check() doesn't import the module, it uses a global
state.
* bpo-41261 => ERROR: This implementation allows to create two instances of the
_ast module, but also to unload one instance (call astmodule_free), because
_astmodule.m_size = -1.
At commit b1cc6ba73a51d5cc3aeb113b5e7378fb50a0e20a ("bpo-41194: Convert _ast
extension to PEP 489 (GH-21293)"):
---------------
static astmodulestate*
get_global_ast_state(void)
{
...
PyObject *module = PyImport_GetModule(name);
if (module == NULL) {
if (PyErr_Occurred()) {
return NULL;
}
module = PyImport_Import(name);
if (module == NULL) {
return NULL;
}
}
...
astmodulestate *state = get_ast_state(module);
Py_DECREF(module);
return state;
}
static struct PyModuleDef _astmodule = {
PyModuleDef_HEAD_INIT,
.m_name = "_ast",
.m_size = sizeof(astmodulestate),
.m_slots = astmodule_slots,
.m_traverse = astmodule_traverse,
.m_clear = astmodule_clear,
.m_free = astmodule_free,
};
PyMODINIT_FUNC
PyInit__ast(void)
{
return PyModuleDef_Init(&_astmodule);
}
---------------
* bpo-41631 => ERROR: PyAST_Check() imports "_ast" module
----------
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Python tracker <[email protected]>
<https://bugs.python.org/issue41631>
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