bpo-41631: _ast module uses again a global state (#21961)
Partially revert commit ac46eb4ad6662cf6d771b20d8963658b2186c48c:
"bpo-38113: Update the Python-ast.c generator to PEP384 (gh-15957)".
Using a module state per module instance is causing subtle practical
problems.
For example, the Mercurial project replaces the __import__() function
to implement lazy import, whereas Python expected that "import _ast"
always return a fully initialized _ast module.
Add _PyAST_Fini() to clear the state at exit.
The _ast module has no state (set _astmodule.m_size to 0). Remove
astmodule_traverse(), astmodule_clear() and astmodule_free()
functions.
diff --git a/Python/Python-ast.c b/Python/Python-ast.c
index 396a683..094010e 100644
--- a/Python/Python-ast.c
+++ b/Python/Python-ast.c
@@ -224,40 +224,35 @@
} astmodulestate;
-static astmodulestate*
-get_ast_state(PyObject *module)
-{
- void *state = PyModule_GetState(module);
- assert(state != NULL);
- return (astmodulestate*)state;
-}
+// Forward declaration
+static int init_types(astmodulestate *state);
+
+// bpo-41194, bpo-41261, bpo-41631: The _ast module uses a global state.
+static astmodulestate global_ast_state = {0};
static astmodulestate*
get_global_ast_state(void)
{
- _Py_IDENTIFIER(_ast);
- PyObject *name = _PyUnicode_FromId(&PyId__ast); // borrowed reference
- if (name == NULL) {
+ astmodulestate* state = &global_ast_state;
+ if (!init_types(state)) {
return NULL;
}
- 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 int astmodule_clear(PyObject *module)
+static astmodulestate*
+get_ast_state(PyObject* Py_UNUSED(module))
{
- astmodulestate *state = get_ast_state(module);
+ astmodulestate* state = get_global_ast_state();
+ // get_ast_state() must only be called after _ast module is imported,
+ // and astmodule_exec() calls init_types()
+ assert(state != NULL);
+ return state;
+}
+
+void _PyAST_Fini(PyThreadState *tstate)
+{
+ astmodulestate* state = &global_ast_state;
Py_CLEAR(state->AST_type);
Py_CLEAR(state->Add_singleton);
Py_CLEAR(state->Add_type);
@@ -472,231 +467,7 @@
Py_CLEAR(state->vararg);
Py_CLEAR(state->withitem_type);
- return 0;
-}
-
-static int astmodule_traverse(PyObject *module, visitproc visit, void* arg)
-{
- astmodulestate *state = get_ast_state(module);
- Py_VISIT(state->AST_type);
- Py_VISIT(state->Add_singleton);
- Py_VISIT(state->Add_type);
- Py_VISIT(state->And_singleton);
- Py_VISIT(state->And_type);
- Py_VISIT(state->AnnAssign_type);
- Py_VISIT(state->Assert_type);
- Py_VISIT(state->Assign_type);
- Py_VISIT(state->AsyncFor_type);
- Py_VISIT(state->AsyncFunctionDef_type);
- Py_VISIT(state->AsyncWith_type);
- Py_VISIT(state->Attribute_type);
- Py_VISIT(state->AugAssign_type);
- Py_VISIT(state->Await_type);
- Py_VISIT(state->BinOp_type);
- Py_VISIT(state->BitAnd_singleton);
- Py_VISIT(state->BitAnd_type);
- Py_VISIT(state->BitOr_singleton);
- Py_VISIT(state->BitOr_type);
- Py_VISIT(state->BitXor_singleton);
- Py_VISIT(state->BitXor_type);
- Py_VISIT(state->BoolOp_type);
- Py_VISIT(state->Break_type);
- Py_VISIT(state->Call_type);
- Py_VISIT(state->ClassDef_type);
- Py_VISIT(state->Compare_type);
- Py_VISIT(state->Constant_type);
- Py_VISIT(state->Continue_type);
- Py_VISIT(state->Del_singleton);
- Py_VISIT(state->Del_type);
- Py_VISIT(state->Delete_type);
- Py_VISIT(state->DictComp_type);
- Py_VISIT(state->Dict_type);
- Py_VISIT(state->Div_singleton);
- Py_VISIT(state->Div_type);
- Py_VISIT(state->Eq_singleton);
- Py_VISIT(state->Eq_type);
- Py_VISIT(state->ExceptHandler_type);
- Py_VISIT(state->Expr_type);
- Py_VISIT(state->Expression_type);
- Py_VISIT(state->FloorDiv_singleton);
- Py_VISIT(state->FloorDiv_type);
- Py_VISIT(state->For_type);
- Py_VISIT(state->FormattedValue_type);
- Py_VISIT(state->FunctionDef_type);
- Py_VISIT(state->FunctionType_type);
- Py_VISIT(state->GeneratorExp_type);
- Py_VISIT(state->Global_type);
- Py_VISIT(state->GtE_singleton);
- Py_VISIT(state->GtE_type);
- Py_VISIT(state->Gt_singleton);
- Py_VISIT(state->Gt_type);
- Py_VISIT(state->IfExp_type);
- Py_VISIT(state->If_type);
- Py_VISIT(state->ImportFrom_type);
- Py_VISIT(state->Import_type);
- Py_VISIT(state->In_singleton);
- Py_VISIT(state->In_type);
- Py_VISIT(state->Interactive_type);
- Py_VISIT(state->Invert_singleton);
- Py_VISIT(state->Invert_type);
- Py_VISIT(state->IsNot_singleton);
- Py_VISIT(state->IsNot_type);
- Py_VISIT(state->Is_singleton);
- Py_VISIT(state->Is_type);
- Py_VISIT(state->JoinedStr_type);
- Py_VISIT(state->LShift_singleton);
- Py_VISIT(state->LShift_type);
- Py_VISIT(state->Lambda_type);
- Py_VISIT(state->ListComp_type);
- Py_VISIT(state->List_type);
- Py_VISIT(state->Load_singleton);
- Py_VISIT(state->Load_type);
- Py_VISIT(state->LtE_singleton);
- Py_VISIT(state->LtE_type);
- Py_VISIT(state->Lt_singleton);
- Py_VISIT(state->Lt_type);
- Py_VISIT(state->MatMult_singleton);
- Py_VISIT(state->MatMult_type);
- Py_VISIT(state->Mod_singleton);
- Py_VISIT(state->Mod_type);
- Py_VISIT(state->Module_type);
- Py_VISIT(state->Mult_singleton);
- Py_VISIT(state->Mult_type);
- Py_VISIT(state->Name_type);
- Py_VISIT(state->NamedExpr_type);
- Py_VISIT(state->Nonlocal_type);
- Py_VISIT(state->NotEq_singleton);
- Py_VISIT(state->NotEq_type);
- Py_VISIT(state->NotIn_singleton);
- Py_VISIT(state->NotIn_type);
- Py_VISIT(state->Not_singleton);
- Py_VISIT(state->Not_type);
- Py_VISIT(state->Or_singleton);
- Py_VISIT(state->Or_type);
- Py_VISIT(state->Pass_type);
- Py_VISIT(state->Pow_singleton);
- Py_VISIT(state->Pow_type);
- Py_VISIT(state->RShift_singleton);
- Py_VISIT(state->RShift_type);
- Py_VISIT(state->Raise_type);
- Py_VISIT(state->Return_type);
- Py_VISIT(state->SetComp_type);
- Py_VISIT(state->Set_type);
- Py_VISIT(state->Slice_type);
- Py_VISIT(state->Starred_type);
- Py_VISIT(state->Store_singleton);
- Py_VISIT(state->Store_type);
- Py_VISIT(state->Sub_singleton);
- Py_VISIT(state->Sub_type);
- Py_VISIT(state->Subscript_type);
- Py_VISIT(state->Try_type);
- Py_VISIT(state->Tuple_type);
- Py_VISIT(state->TypeIgnore_type);
- Py_VISIT(state->UAdd_singleton);
- Py_VISIT(state->UAdd_type);
- Py_VISIT(state->USub_singleton);
- Py_VISIT(state->USub_type);
- Py_VISIT(state->UnaryOp_type);
- Py_VISIT(state->While_type);
- Py_VISIT(state->With_type);
- Py_VISIT(state->YieldFrom_type);
- Py_VISIT(state->Yield_type);
- Py_VISIT(state->__dict__);
- Py_VISIT(state->__doc__);
- Py_VISIT(state->__module__);
- Py_VISIT(state->_attributes);
- Py_VISIT(state->_fields);
- Py_VISIT(state->alias_type);
- Py_VISIT(state->annotation);
- Py_VISIT(state->arg);
- Py_VISIT(state->arg_type);
- Py_VISIT(state->args);
- Py_VISIT(state->argtypes);
- Py_VISIT(state->arguments_type);
- Py_VISIT(state->asname);
- Py_VISIT(state->ast);
- Py_VISIT(state->attr);
- Py_VISIT(state->bases);
- Py_VISIT(state->body);
- Py_VISIT(state->boolop_type);
- Py_VISIT(state->cause);
- Py_VISIT(state->cmpop_type);
- Py_VISIT(state->col_offset);
- Py_VISIT(state->comparators);
- Py_VISIT(state->comprehension_type);
- Py_VISIT(state->context_expr);
- Py_VISIT(state->conversion);
- Py_VISIT(state->ctx);
- Py_VISIT(state->decorator_list);
- Py_VISIT(state->defaults);
- Py_VISIT(state->elt);
- Py_VISIT(state->elts);
- Py_VISIT(state->end_col_offset);
- Py_VISIT(state->end_lineno);
- Py_VISIT(state->exc);
- Py_VISIT(state->excepthandler_type);
- Py_VISIT(state->expr_context_type);
- Py_VISIT(state->expr_type);
- Py_VISIT(state->finalbody);
- Py_VISIT(state->format_spec);
- Py_VISIT(state->func);
- Py_VISIT(state->generators);
- Py_VISIT(state->handlers);
- Py_VISIT(state->id);
- Py_VISIT(state->ifs);
- Py_VISIT(state->is_async);
- Py_VISIT(state->items);
- Py_VISIT(state->iter);
- Py_VISIT(state->key);
- Py_VISIT(state->keys);
- Py_VISIT(state->keyword_type);
- Py_VISIT(state->keywords);
- Py_VISIT(state->kind);
- Py_VISIT(state->kw_defaults);
- Py_VISIT(state->kwarg);
- Py_VISIT(state->kwonlyargs);
- Py_VISIT(state->left);
- Py_VISIT(state->level);
- Py_VISIT(state->lineno);
- Py_VISIT(state->lower);
- Py_VISIT(state->mod_type);
- Py_VISIT(state->module);
- Py_VISIT(state->msg);
- Py_VISIT(state->name);
- Py_VISIT(state->names);
- Py_VISIT(state->op);
- Py_VISIT(state->operand);
- Py_VISIT(state->operator_type);
- Py_VISIT(state->ops);
- Py_VISIT(state->optional_vars);
- Py_VISIT(state->orelse);
- Py_VISIT(state->posonlyargs);
- Py_VISIT(state->returns);
- Py_VISIT(state->right);
- Py_VISIT(state->simple);
- Py_VISIT(state->slice);
- Py_VISIT(state->step);
- Py_VISIT(state->stmt_type);
- Py_VISIT(state->tag);
- Py_VISIT(state->target);
- Py_VISIT(state->targets);
- Py_VISIT(state->test);
- Py_VISIT(state->type);
- Py_VISIT(state->type_comment);
- Py_VISIT(state->type_ignore_type);
- Py_VISIT(state->type_ignores);
- Py_VISIT(state->unaryop_type);
- Py_VISIT(state->upper);
- Py_VISIT(state->value);
- Py_VISIT(state->values);
- Py_VISIT(state->vararg);
- Py_VISIT(state->withitem_type);
-
- return 0;
-}
-
-static void astmodule_free(void* module) {
- astmodule_clear((PyObject*)module);
+ state->initialized = 0;
}
static int init_identifiers(astmodulestate *state)
@@ -10316,11 +10087,9 @@
static struct PyModuleDef _astmodule = {
PyModuleDef_HEAD_INIT,
.m_name = "_ast",
- .m_size = sizeof(astmodulestate),
+ // The _ast module uses a global state (global_ast_state).
+ .m_size = 0,
.m_slots = astmodule_slots,
- .m_traverse = astmodule_traverse,
- .m_clear = astmodule_clear,
- .m_free = astmodule_free,
};
PyMODINIT_FUNC
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index ab5a676..75d5780 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -1259,6 +1259,12 @@
static void
finalize_interp_types(PyThreadState *tstate)
{
+ // The _ast module state is shared by all interpreters.
+ // The state must only be cleared by the main interpreter.
+ if (_Py_IsMainInterpreter(tstate)) {
+ _PyAST_Fini(tstate);
+ }
+
_PyExc_Fini(tstate);
_PyFrame_Fini(tstate);
_PyAsyncGen_Fini(tstate);