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bpo-41194: Convert _ast extension to PEP 489 (GH-21293)
Convert the _ast extension module to PEP 489 "Multiphase initialization". Replace the global _ast state with a module state.
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2 files changed

+247
-195
lines changed

2 files changed

+247
-195
lines changed

Parser/asdl_c.py

+73-46
Original file line numberDiff line numberDiff line change
@@ -692,6 +692,9 @@ def visitModule(self, mod):
692692
int res = -1;
693693
PyObject *key, *value, *fields;
694694
astmodulestate *state = get_global_ast_state();
695+
if (state == NULL) {
696+
goto cleanup;
697+
}
695698
if (_PyObject_LookupAttr((PyObject*)Py_TYPE(self), state->_fields, &fields) < 0) {
696699
goto cleanup;
697700
}
@@ -761,6 +764,10 @@ def visitModule(self, mod):
761764
ast_type_reduce(PyObject *self, PyObject *unused)
762765
{
763766
astmodulestate *state = get_global_ast_state();
767+
if (state == NULL) {
768+
return NULL;
769+
}
770+
764771
PyObject *dict;
765772
if (_PyObject_LookupAttr(self, state->__dict__, &dict) < 0) {
766773
return NULL;
@@ -969,9 +976,8 @@ def visitModule(self, mod):
969976
970977
""", 0, reflow=False)
971978

972-
self.emit("static int init_types(void)",0)
979+
self.emit("static int init_types(astmodulestate *state)",0)
973980
self.emit("{", 0)
974-
self.emit("astmodulestate *state = get_global_ast_state();", 1)
975981
self.emit("if (state->initialized) return 1;", 1)
976982
self.emit("if (init_identifiers(state) < 0) return 0;", 1)
977983
self.emit("state->AST_type = PyType_FromSpec(&AST_type_spec);", 1)
@@ -1046,40 +1052,55 @@ def emit_defaults(self, name, fields, depth):
10461052
class ASTModuleVisitor(PickleVisitor):
10471053

10481054
def visitModule(self, mod):
1049-
self.emit("PyMODINIT_FUNC", 0)
1050-
self.emit("PyInit__ast(void)", 0)
1055+
self.emit("static int", 0)
1056+
self.emit("astmodule_exec(PyObject *m)", 0)
10511057
self.emit("{", 0)
1052-
self.emit("PyObject *m = PyModule_Create(&_astmodule);", 1)
1053-
self.emit("if (!m) {", 1)
1054-
self.emit("return NULL;", 2)
1055-
self.emit("}", 1)
10561058
self.emit('astmodulestate *state = get_ast_state(m);', 1)
1057-
self.emit('', 1)
1059+
self.emit("", 0)
10581060

1059-
self.emit("if (!init_types()) {", 1)
1060-
self.emit("goto error;", 2)
1061+
self.emit("if (!init_types(state)) {", 1)
1062+
self.emit("return -1;", 2)
10611063
self.emit("}", 1)
10621064
self.emit('if (PyModule_AddObject(m, "AST", state->AST_type) < 0) {', 1)
1063-
self.emit('goto error;', 2)
1065+
self.emit('return -1;', 2)
10641066
self.emit('}', 1)
10651067
self.emit('Py_INCREF(state->AST_type);', 1)
10661068
self.emit('if (PyModule_AddIntMacro(m, PyCF_ALLOW_TOP_LEVEL_AWAIT) < 0) {', 1)
1067-
self.emit("goto error;", 2)
1069+
self.emit("return -1;", 2)
10681070
self.emit('}', 1)
10691071
self.emit('if (PyModule_AddIntMacro(m, PyCF_ONLY_AST) < 0) {', 1)
1070-
self.emit("goto error;", 2)
1072+
self.emit("return -1;", 2)
10711073
self.emit('}', 1)
10721074
self.emit('if (PyModule_AddIntMacro(m, PyCF_TYPE_COMMENTS) < 0) {', 1)
1073-
self.emit("goto error;", 2)
1075+
self.emit("return -1;", 2)
10741076
self.emit('}', 1)
10751077
for dfn in mod.dfns:
10761078
self.visit(dfn)
1077-
self.emit("return m;", 1)
1078-
self.emit("", 0)
1079-
self.emit("error:", 0)
1080-
self.emit("Py_DECREF(m);", 1)
1081-
self.emit("return NULL;", 1)
1079+
self.emit("return 0;", 1)
10821080
self.emit("}", 0)
1081+
self.emit("", 0)
1082+
self.emit("""
1083+
static PyModuleDef_Slot astmodule_slots[] = {
1084+
{Py_mod_exec, astmodule_exec},
1085+
{0, NULL}
1086+
};
1087+
1088+
static struct PyModuleDef _astmodule = {
1089+
PyModuleDef_HEAD_INIT,
1090+
.m_name = "_ast",
1091+
.m_size = sizeof(astmodulestate),
1092+
.m_slots = astmodule_slots,
1093+
.m_traverse = astmodule_traverse,
1094+
.m_clear = astmodule_clear,
1095+
.m_free = astmodule_free,
1096+
};
1097+
1098+
PyMODINIT_FUNC
1099+
PyInit__ast(void)
1100+
{
1101+
return PyModuleDef_Init(&_astmodule);
1102+
}
1103+
""".strip(), 0, reflow=False)
10831104

10841105
def visitProduct(self, prod, name):
10851106
self.addObj(name)
@@ -1095,7 +1116,7 @@ def visitConstructor(self, cons, name):
10951116
def addObj(self, name):
10961117
self.emit("if (PyModule_AddObject(m, \"%s\", "
10971118
"state->%s_type) < 0) {" % (name, name), 1)
1098-
self.emit("goto error;", 2)
1119+
self.emit("return -1;", 2)
10991120
self.emit('}', 1)
11001121
self.emit("Py_INCREF(state->%s_type);" % name, 1)
11011122

@@ -1255,11 +1276,10 @@ class PartingShots(StaticVisitor):
12551276
CODE = """
12561277
PyObject* PyAST_mod2obj(mod_ty t)
12571278
{
1258-
if (!init_types()) {
1279+
astmodulestate *state = get_global_ast_state();
1280+
if (state == NULL) {
12591281
return NULL;
12601282
}
1261-
1262-
astmodulestate *state = get_global_ast_state();
12631283
return ast2obj_mod(state, t);
12641284
}
12651285
@@ -1281,10 +1301,6 @@ class PartingShots(StaticVisitor):
12811301
12821302
assert(0 <= mode && mode <= 2);
12831303
1284-
if (!init_types()) {
1285-
return NULL;
1286-
}
1287-
12881304
isinstance = PyObject_IsInstance(ast, req_type[mode]);
12891305
if (isinstance == -1)
12901306
return NULL;
@@ -1303,11 +1319,10 @@ class PartingShots(StaticVisitor):
13031319
13041320
int PyAST_Check(PyObject* obj)
13051321
{
1306-
if (!init_types()) {
1322+
astmodulestate *state = get_global_ast_state();
1323+
if (state == NULL) {
13071324
return -1;
13081325
}
1309-
1310-
astmodulestate *state = get_global_ast_state();
13111326
return PyObject_IsInstance(obj, state->AST_type);
13121327
}
13131328
"""
@@ -1358,12 +1373,35 @@ def generate_module_def(f, mod):
13581373
f.write(' PyObject *' + s + ';\n')
13591374
f.write('} astmodulestate;\n\n')
13601375
f.write("""
1361-
static astmodulestate global_ast_state;
1376+
static astmodulestate*
1377+
get_ast_state(PyObject *module)
1378+
{
1379+
void *state = PyModule_GetState(module);
1380+
assert(state != NULL);
1381+
return (astmodulestate*)state;
1382+
}
13621383
1363-
static astmodulestate *
1364-
get_ast_state(PyObject *Py_UNUSED(module))
1384+
static astmodulestate*
1385+
get_global_ast_state(void)
13651386
{
1366-
return &global_ast_state;
1387+
_Py_IDENTIFIER(_ast);
1388+
PyObject *name = _PyUnicode_FromId(&PyId__ast); // borrowed reference
1389+
if (name == NULL) {
1390+
return NULL;
1391+
}
1392+
PyObject *module = PyImport_GetModule(name);
1393+
if (module == NULL) {
1394+
if (PyErr_Occurred()) {
1395+
return NULL;
1396+
}
1397+
module = PyImport_Import(name);
1398+
if (module == NULL) {
1399+
return NULL;
1400+
}
1401+
}
1402+
astmodulestate *state = get_ast_state(module);
1403+
Py_DECREF(module);
1404+
return state;
13671405
}
13681406
13691407
static int astmodule_clear(PyObject *module)
@@ -1390,17 +1428,6 @@ def generate_module_def(f, mod):
13901428
astmodule_clear((PyObject*)module);
13911429
}
13921430
1393-
static struct PyModuleDef _astmodule = {
1394-
PyModuleDef_HEAD_INIT,
1395-
.m_name = "_ast",
1396-
.m_size = -1,
1397-
.m_traverse = astmodule_traverse,
1398-
.m_clear = astmodule_clear,
1399-
.m_free = astmodule_free,
1400-
};
1401-
1402-
#define get_global_ast_state() (&global_ast_state)
1403-
14041431
""")
14051432
f.write('static int init_identifiers(astmodulestate *state)\n')
14061433
f.write('{\n')

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