From d87d2128422ab3a37563d6d6501a395724fb53f5 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Mon, 22 Apr 2024 15:31:10 -0600
Subject: [PATCH 01/11] Factor out fix_up_extension_for_interpreter().

---
 Include/internal/pycore_import.h |   1 +
 Python/import.c                  | 100 ++++++++++++++++++++++---------
 2 files changed, 72 insertions(+), 29 deletions(-)

diff --git a/Include/internal/pycore_import.h b/Include/internal/pycore_import.h
index 08af53258cde97..3bde64daa87e62 100644
--- a/Include/internal/pycore_import.h
+++ b/Include/internal/pycore_import.h
@@ -28,6 +28,7 @@ extern int _PyImport_FixupBuiltin(
     const char *name,            /* UTF-8 encoded string */
     PyObject *modules
     );
+// We could probably drop this:
 extern int _PyImport_FixupExtensionObject(PyObject*, PyObject *,
                                           PyObject *, PyObject *);
 
diff --git a/Python/import.c b/Python/import.c
index 8cdc04f03dd201..c1076501a133ed 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -200,16 +200,22 @@ _PyImport_ClearModules(PyInterpreterState *interp)
     Py_SETREF(MODULES(interp), NULL);
 }
 
-PyObject *
-PyImport_GetModuleDict(void)
+static inline PyObject *
+get_modules_dict(PyInterpreterState *interp)
 {
-    PyInterpreterState *interp = _PyInterpreterState_GET();
     if (MODULES(interp) == NULL) {
         Py_FatalError("interpreter has no modules dictionary");
     }
     return MODULES(interp);
 }
 
+PyObject *
+PyImport_GetModuleDict(void)
+{
+    PyInterpreterState *interp = _PyInterpreterState_GET();
+    return get_modules_dict(interp);
+}
+
 int
 _PyImport_SetModule(PyObject *name, PyObject *m)
 {
@@ -894,7 +900,7 @@ extensions_lock_release(void)
    (module name, module name)  (for built-in modules) or by
    (filename, module name) (for dynamically loaded modules), containing these
    modules.  A copy of the module's dictionary is stored by calling
-   _PyImport_FixupExtensionObject() immediately after the module initialization
+   fix_up_extension() immediately after the module initialization
    function succeeds.  A copy can be retrieved from there by calling
    import_find_extension().
 
@@ -1159,28 +1165,57 @@ is_core_module(PyInterpreterState *interp, PyObject *name, PyObject *path)
 }
 
 static int
-fix_up_extension(PyObject *mod, PyObject *name, PyObject *path)
+fix_up_extension_for_interpreter(PyInterpreterState *interp,
+                                 PyObject *mod, PyModuleDef *def,
+                                 PyObject *name, PyObject *path,
+                                 PyObject *modules)
 {
-    if (mod == NULL || !PyModule_Check(mod)) {
-        PyErr_BadInternalCall();
+    assert(mod != NULL && PyModule_Check(mod));
+    assert(def == PyModule_GetDef(mod));
+
+    if (modules == NULL) {
+        modules = get_modules_dict(interp);
+    }
+    if (PyObject_SetItem(modules, name, mod) < 0) {
         return -1;
     }
 
-    struct PyModuleDef *def = PyModule_GetDef(mod);
-    if (!def) {
-        PyErr_BadInternalCall();
-        return -1;
+    if (_modules_by_index_set(interp, def, mod) < 0) {
+        goto error;
     }
 
-    PyThreadState *tstate = _PyThreadState_GET();
-    if (_modules_by_index_set(tstate->interp, def, mod) < 0) {
+    return 0;
+
+error:
+    PyMapping_DelItem(modules, name);
+    return -1;
+}
+
+
+static int
+fix_up_extension(PyObject *mod, PyModuleDef *def,
+                 PyObject *name, PyObject *path,
+                 PyObject *modules)
+{
+    PyInterpreterState *interp = _PyInterpreterState_GET();
+    if (def == NULL) {
+        def = PyModule_GetDef(mod);
+        if (def == NULL) {
+            PyErr_BadInternalCall();
+            return -1;
+        }
+    }
+
+    if (fix_up_extension_for_interpreter(
+                interp, mod, def, name, path, modules) < 0)
+    {
         return -1;
     }
 
     // bpo-44050: Extensions and def->m_base.m_copy can be updated
     // when the extension module doesn't support sub-interpreters.
     if (def->m_size == -1) {
-        if (!is_core_module(tstate->interp, name, path)) {
+        if (!is_core_module(interp, name, path)) {
             assert(PyUnicode_CompareWithASCIIString(name, "sys") != 0);
             assert(PyUnicode_CompareWithASCIIString(name, "builtins") != 0);
             if (def->m_base.m_copy) {
@@ -1191,34 +1226,43 @@ fix_up_extension(PyObject *mod, PyObject *name, PyObject *path)
             }
             PyObject *dict = PyModule_GetDict(mod);
             if (dict == NULL) {
-                return -1;
+                goto error;
             }
             def->m_base.m_copy = PyDict_Copy(dict);
             if (def->m_base.m_copy == NULL) {
-                return -1;
+                goto error;
             }
         }
     }
 
     // XXX Why special-case the main interpreter?
-    if (_Py_IsMainInterpreter(tstate->interp) || def->m_size == -1) {
+    if (_Py_IsMainInterpreter(interp) || def->m_size == -1) {
+#ifndef NDEBUG
+        PyModuleDef *cached = _extensions_cache_get(path, name);
+        assert(cached == NULL || cached == def);
+#endif
         if (_extensions_cache_set(path, name, def) < 0) {
-            return -1;
+            goto error;
         }
     }
 
     return 0;
+
+
+error:
+    PyMapping_DelItem(modules, name);
+    return -1;
 }
 
 int
 _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
                                PyObject *filename, PyObject *modules)
 {
-    if (PyObject_SetItem(modules, name, mod) < 0) {
+    if (mod == NULL || !PyModule_Check(mod)) {
+        PyErr_BadInternalCall();
         return -1;
     }
-    if (fix_up_extension(mod, name, filename) < 0) {
-        PyMapping_DelItem(modules, name);
+    if (fix_up_extension(mod, NULL, name, filename, modules) < 0) {
         return -1;
     }
     return 0;
@@ -1350,11 +1394,7 @@ _PyImport_FixupBuiltin(PyObject *mod, const char *name, PyObject *modules)
         goto finally;
     }
 
-    if (PyObject_SetItem(modules, nameobj, mod) < 0) {
-        goto finally;
-    }
-    if (fix_up_extension(mod, nameobj, nameobj) < 0) {
-        PyMapping_DelItem(modules, nameobj);
+    if (fix_up_extension(mod, def, nameobj, nameobj, modules) < 0) {
         goto finally;
     }
 
@@ -1391,7 +1431,6 @@ create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
         return mod;
     }
 
-    PyObject *modules = MODULES(tstate->interp);
     struct _inittab *found = NULL;
     for (struct _inittab *p = INITTAB; p->name != NULL; p++) {
         if (_PyUnicode_EqualToASCIIString(name, p->name)) {
@@ -1419,14 +1458,17 @@ create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
         return PyModule_FromDefAndSpec((PyModuleDef*)mod, spec);
     }
     else {
-        /* Remember pointer to module init function. */
+        assert(PyModule_Check(mod));
         PyModuleDef *def = PyModule_GetDef(mod);
         if (def == NULL) {
             return NULL;
         }
 
+        /* Remember pointer to module init function. */
         def->m_base.m_init = p0;
-        if (_PyImport_FixupExtensionObject(mod, name, name, modules) < 0) {
+
+        PyObject *modules = MODULES(tstate->interp);
+        if (fix_up_extension(mod, def, name, name, modules) < 0) {
             return NULL;
         }
         return mod;

From b85c5afb269197d4724be688050b99605ce9e985 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Wed, 17 Apr 2024 11:31:31 -0600
Subject: [PATCH 02/11] Pass tstate through to fix_up_extension().

---
 Include/internal/pycore_import.h |  1 +
 Python/import.c                  | 25 +++++++++++++------------
 Python/pylifecycle.c             |  2 +-
 Python/sysmodule.c               |  2 +-
 4 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/Include/internal/pycore_import.h b/Include/internal/pycore_import.h
index 3bde64daa87e62..8d7f0543f8d315 100644
--- a/Include/internal/pycore_import.h
+++ b/Include/internal/pycore_import.h
@@ -24,6 +24,7 @@ extern int _PyImport_ReleaseLock(PyInterpreterState *interp);
 
 // This is used exclusively for the sys and builtins modules:
 extern int _PyImport_FixupBuiltin(
+    PyThreadState *tstate,
     PyObject *mod,
     const char *name,            /* UTF-8 encoded string */
     PyObject *modules
diff --git a/Python/import.c b/Python/import.c
index c1076501a133ed..8779350d4d196c 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1165,7 +1165,7 @@ is_core_module(PyInterpreterState *interp, PyObject *name, PyObject *path)
 }
 
 static int
-fix_up_extension_for_interpreter(PyInterpreterState *interp,
+fix_up_extension_for_interpreter(PyThreadState *tstate,
                                  PyObject *mod, PyModuleDef *def,
                                  PyObject *name, PyObject *path,
                                  PyObject *modules)
@@ -1174,13 +1174,13 @@ fix_up_extension_for_interpreter(PyInterpreterState *interp,
     assert(def == PyModule_GetDef(mod));
 
     if (modules == NULL) {
-        modules = get_modules_dict(interp);
+        modules = get_modules_dict(tstate->interp);
     }
     if (PyObject_SetItem(modules, name, mod) < 0) {
         return -1;
     }
 
-    if (_modules_by_index_set(interp, def, mod) < 0) {
+    if (_modules_by_index_set(tstate->interp, def, mod) < 0) {
         goto error;
     }
 
@@ -1193,11 +1193,10 @@ fix_up_extension_for_interpreter(PyInterpreterState *interp,
 
 
 static int
-fix_up_extension(PyObject *mod, PyModuleDef *def,
+fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
                  PyObject *name, PyObject *path,
                  PyObject *modules)
 {
-    PyInterpreterState *interp = _PyInterpreterState_GET();
     if (def == NULL) {
         def = PyModule_GetDef(mod);
         if (def == NULL) {
@@ -1207,7 +1206,7 @@ fix_up_extension(PyObject *mod, PyModuleDef *def,
     }
 
     if (fix_up_extension_for_interpreter(
-                interp, mod, def, name, path, modules) < 0)
+                tstate, mod, def, name, path, modules) < 0)
     {
         return -1;
     }
@@ -1215,7 +1214,7 @@ fix_up_extension(PyObject *mod, PyModuleDef *def,
     // bpo-44050: Extensions and def->m_base.m_copy can be updated
     // when the extension module doesn't support sub-interpreters.
     if (def->m_size == -1) {
-        if (!is_core_module(interp, name, path)) {
+        if (!is_core_module(tstate->interp, name, path)) {
             assert(PyUnicode_CompareWithASCIIString(name, "sys") != 0);
             assert(PyUnicode_CompareWithASCIIString(name, "builtins") != 0);
             if (def->m_base.m_copy) {
@@ -1236,7 +1235,7 @@ fix_up_extension(PyObject *mod, PyModuleDef *def,
     }
 
     // XXX Why special-case the main interpreter?
-    if (_Py_IsMainInterpreter(interp) || def->m_size == -1) {
+    if (_Py_IsMainInterpreter(tstate->interp) || def->m_size == -1) {
 #ifndef NDEBUG
         PyModuleDef *cached = _extensions_cache_get(path, name);
         assert(cached == NULL || cached == def);
@@ -1262,7 +1261,8 @@ _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
         PyErr_BadInternalCall();
         return -1;
     }
-    if (fix_up_extension(mod, NULL, name, filename, modules) < 0) {
+    PyThreadState *tstate = _PyThreadState_GET();
+    if (fix_up_extension(tstate, mod, NULL, name, filename, modules) < 0) {
         return -1;
     }
     return 0;
@@ -1377,7 +1377,8 @@ clear_singlephase_extension(PyInterpreterState *interp,
 /*******************/
 
 int
-_PyImport_FixupBuiltin(PyObject *mod, const char *name, PyObject *modules)
+_PyImport_FixupBuiltin(PyThreadState *tstate, PyObject *mod, const char *name,
+                       PyObject *modules)
 {
     int res = -1;
     assert(mod != NULL && PyModule_Check(mod));
@@ -1394,7 +1395,7 @@ _PyImport_FixupBuiltin(PyObject *mod, const char *name, PyObject *modules)
         goto finally;
     }
 
-    if (fix_up_extension(mod, def, nameobj, nameobj, modules) < 0) {
+    if (fix_up_extension(tstate, mod, def, nameobj, nameobj, modules) < 0) {
         goto finally;
     }
 
@@ -1468,7 +1469,7 @@ create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
         def->m_base.m_init = p0;
 
         PyObject *modules = MODULES(tstate->interp);
-        if (fix_up_extension(mod, def, name, name, modules) < 0) {
+        if (fix_up_extension(tstate, mod, def, name, name, modules) < 0) {
             return NULL;
         }
         return mod;
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index cc1824634e7a7f..0f3ca4a6687514 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -777,7 +777,7 @@ pycore_init_builtins(PyThreadState *tstate)
     }
 
     PyObject *modules = _PyImport_GetModules(interp);
-    if (_PyImport_FixupBuiltin(bimod, "builtins", modules) < 0) {
+    if (_PyImport_FixupBuiltin(tstate, bimod, "builtins", modules) < 0) {
         goto error;
     }
 
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 05ee4051a20e18..7af363678e8e86 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -3764,7 +3764,7 @@ _PySys_Create(PyThreadState *tstate, PyObject **sysmod_p)
         return status;
     }
 
-    if (_PyImport_FixupBuiltin(sysmod, "sys", modules) < 0) {
+    if (_PyImport_FixupBuiltin(tstate, sysmod, "sys", modules) < 0) {
         goto error;
     }
 

From 319c4613182d9b42c447b2255dd699a63900dd0c Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Thu, 18 Apr 2024 19:16:44 -0600
Subject: [PATCH 03/11] We already know the def is okay.

---
 Python/import.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/Python/import.c b/Python/import.c
index 8779350d4d196c..ef32720146b00b 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1197,13 +1197,8 @@ fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
                  PyObject *name, PyObject *path,
                  PyObject *modules)
 {
-    if (def == NULL) {
-        def = PyModule_GetDef(mod);
-        if (def == NULL) {
-            PyErr_BadInternalCall();
-            return -1;
-        }
-    }
+    assert(mod != NULL && PyModule_Check(mod));
+    assert(def == _PyModule_GetDef(mod));
 
     if (fix_up_extension_for_interpreter(
                 tstate, mod, def, name, path, modules) < 0)
@@ -1247,7 +1242,6 @@ fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
 
     return 0;
 
-
 error:
     PyMapping_DelItem(modules, name);
     return -1;
@@ -1261,8 +1255,14 @@ _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
         PyErr_BadInternalCall();
         return -1;
     }
+    PyModuleDef *def = PyModule_GetDef(mod);
+    if (def == NULL) {
+        PyErr_BadInternalCall();
+        return -1;
+    }
+
     PyThreadState *tstate = _PyThreadState_GET();
-    if (fix_up_extension(tstate, mod, NULL, name, filename, modules) < 0) {
+    if (fix_up_extension(tstate, mod, def, name, filename, modules) < 0) {
         return -1;
     }
     return 0;

From e6ea054525ee34af451c07eb8b7dcf2738d7ce85 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Fri, 19 Apr 2024 14:36:40 -0600
Subject: [PATCH 04/11] Let the modules arg to
 fix_up_extension_for_interpreter() be NULL.

---
 Python/import.c | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/Python/import.c b/Python/import.c
index ef32720146b00b..3685e622e798a3 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1167,28 +1167,22 @@ is_core_module(PyInterpreterState *interp, PyObject *name, PyObject *path)
 static int
 fix_up_extension_for_interpreter(PyThreadState *tstate,
                                  PyObject *mod, PyModuleDef *def,
-                                 PyObject *name, PyObject *path,
-                                 PyObject *modules)
+                                 PyObject *name, PyObject *modules)
 {
     assert(mod != NULL && PyModule_Check(mod));
     assert(def == PyModule_GetDef(mod));
 
-    if (modules == NULL) {
-        modules = get_modules_dict(tstate->interp);
-    }
-    if (PyObject_SetItem(modules, name, mod) < 0) {
+    if (_modules_by_index_set(tstate->interp, def, mod) < 0) {
         return -1;
     }
 
-    if (_modules_by_index_set(tstate->interp, def, mod) < 0) {
-        goto error;
+    if (modules != NULL) {
+        if (PyObject_SetItem(modules, name, mod) < 0) {
+            return -1;
+        }
     }
 
     return 0;
-
-error:
-    PyMapping_DelItem(modules, name);
-    return -1;
 }
 
 
@@ -1201,7 +1195,7 @@ fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
     assert(def == _PyModule_GetDef(mod));
 
     if (fix_up_extension_for_interpreter(
-                tstate, mod, def, name, path, modules) < 0)
+                tstate, mod, def, name, modules) < 0)
     {
         return -1;
     }

From 439661f496715e944c217f4611c13e4aee395a47 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Wed, 17 Apr 2024 12:43:19 -0600
Subject: [PATCH 05/11] Always expect a valid modules dict passed to
 fix_up_extension().

---
 Python/import.c | 45 ++++++++++++++++++++++++++-------------------
 1 file changed, 26 insertions(+), 19 deletions(-)

diff --git a/Python/import.c b/Python/import.c
index 3685e622e798a3..d0c81bc9089550 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -201,44 +201,53 @@ _PyImport_ClearModules(PyInterpreterState *interp)
 }
 
 static inline PyObject *
-get_modules_dict(PyInterpreterState *interp)
+get_modules_dict(PyThreadState *tstate, bool fatal)
 {
-    if (MODULES(interp) == NULL) {
-        Py_FatalError("interpreter has no modules dictionary");
+    /* Technically, it would make sense to incref the dict,
+     * since sys.modules could be swapped out and decref'ed to 0
+     * before the caller is done using it.  However, that is highly
+     * unlikely, especially since we can rely on a global lock
+     * (i.e. the GIL) for thread-safety. */
+    PyObject *modules = MODULES(tstate->interp);
+    if (modules == NULL) {
+        if (fatal) {
+            Py_FatalError("interpreter has no modules dictionary");
+        }
+        _PyErr_SetString(tstate, PyExc_RuntimeError,
+                         "unable to get sys.modules");
+        return NULL;
     }
-    return MODULES(interp);
+    return modules;
 }
 
 PyObject *
 PyImport_GetModuleDict(void)
 {
-    PyInterpreterState *interp = _PyInterpreterState_GET();
-    return get_modules_dict(interp);
+    PyThreadState *tstate = _PyThreadState_GET();
+    return get_modules_dict(tstate, true);
 }
 
 int
 _PyImport_SetModule(PyObject *name, PyObject *m)
 {
-    PyInterpreterState *interp = _PyInterpreterState_GET();
-    PyObject *modules = MODULES(interp);
+    PyThreadState *tstate = _PyThreadState_GET();
+    PyObject *modules = get_modules_dict(tstate, true);
     return PyObject_SetItem(modules, name, m);
 }
 
 int
 _PyImport_SetModuleString(const char *name, PyObject *m)
 {
-    PyInterpreterState *interp = _PyInterpreterState_GET();
-    PyObject *modules = MODULES(interp);
+    PyThreadState *tstate = _PyThreadState_GET();
+    PyObject *modules = get_modules_dict(tstate, true);
     return PyMapping_SetItemString(modules, name, m);
 }
 
 static PyObject *
 import_get_module(PyThreadState *tstate, PyObject *name)
 {
-    PyObject *modules = MODULES(tstate->interp);
+    PyObject *modules = get_modules_dict(tstate, false);
     if (modules == NULL) {
-        _PyErr_SetString(tstate, PyExc_RuntimeError,
-                         "unable to get sys.modules");
         return NULL;
     }
 
@@ -303,10 +312,8 @@ PyImport_GetModule(PyObject *name)
 static PyObject *
 import_add_module(PyThreadState *tstate, PyObject *name)
 {
-    PyObject *modules = MODULES(tstate->interp);
+    PyObject *modules = get_modules_dict(tstate, false);
     if (modules == NULL) {
-        _PyErr_SetString(tstate, PyExc_RuntimeError,
-                         "no import module dictionary");
         return NULL;
     }
 
@@ -403,7 +410,7 @@ remove_module(PyThreadState *tstate, PyObject *name)
 {
     PyObject *exc = _PyErr_GetRaisedException(tstate);
 
-    PyObject *modules = MODULES(tstate->interp);
+    PyObject *modules = get_modules_dict(tstate, true);
     if (PyDict_CheckExact(modules)) {
         // Error is reported to the caller
         (void)PyDict_Pop(modules, name, NULL);
@@ -1283,7 +1290,7 @@ import_find_extension(PyThreadState *tstate, PyObject *name,
     }
 
     PyObject *mod, *mdict;
-    PyObject *modules = MODULES(tstate->interp);
+    PyObject *modules = get_modules_dict(tstate, true);
 
     if (def->m_size == -1) {
         PyObject *m_copy = def->m_base.m_copy;
@@ -1462,7 +1469,7 @@ create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
         /* Remember pointer to module init function. */
         def->m_base.m_init = p0;
 
-        PyObject *modules = MODULES(tstate->interp);
+        PyObject *modules = get_modules_dict(tstate, true);
         if (fix_up_extension(tstate, mod, def, name, name, modules) < 0) {
             return NULL;
         }

From 0d28e0faa47c80797fd3323d6c11f2590ec785eb Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Tue, 23 Apr 2024 08:38:54 -0600
Subject: [PATCH 06/11] Do interpreter fixups after the extension cache, not
 before.

---
 Python/import.c | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/Python/import.c b/Python/import.c
index d0c81bc9089550..5cf55dd2a74a2a 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1192,7 +1192,6 @@ fix_up_extension_for_interpreter(PyThreadState *tstate,
     return 0;
 }
 
-
 static int
 fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
                  PyObject *name, PyObject *path,
@@ -1201,12 +1200,6 @@ fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
     assert(mod != NULL && PyModule_Check(mod));
     assert(def == _PyModule_GetDef(mod));
 
-    if (fix_up_extension_for_interpreter(
-                tstate, mod, def, name, modules) < 0)
-    {
-        return -1;
-    }
-
     // bpo-44050: Extensions and def->m_base.m_copy can be updated
     // when the extension module doesn't support sub-interpreters.
     if (def->m_size == -1) {
@@ -1221,11 +1214,11 @@ fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
             }
             PyObject *dict = PyModule_GetDict(mod);
             if (dict == NULL) {
-                goto error;
+                return -1;
             }
             def->m_base.m_copy = PyDict_Copy(dict);
             if (def->m_base.m_copy == NULL) {
-                goto error;
+                return -1;
             }
         }
     }
@@ -1237,15 +1230,17 @@ fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
         assert(cached == NULL || cached == def);
 #endif
         if (_extensions_cache_set(path, name, def) < 0) {
-            goto error;
+            return -1;
         }
     }
 
-    return 0;
+    if (fix_up_extension_for_interpreter(
+                tstate, mod, def, name, modules) < 0)
+    {
+        return -1;
+    }
 
-error:
-    PyMapping_DelItem(modules, name);
-    return -1;
+    return 0;
 }
 
 int

From abd69f44136d345328fe79190dd0e8557ef6d51a Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Tue, 23 Apr 2024 08:49:25 -0600
Subject: [PATCH 07/11] Call fix_up_extension_for_interpreter() separately.

---
 Python/import.c | 30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/Python/import.c b/Python/import.c
index 5cf55dd2a74a2a..cfc70498d1cfad 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1194,8 +1194,7 @@ fix_up_extension_for_interpreter(PyThreadState *tstate,
 
 static int
 fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
-                 PyObject *name, PyObject *path,
-                 PyObject *modules)
+                 PyObject *name, PyObject *path)
 {
     assert(mod != NULL && PyModule_Check(mod));
     assert(def == _PyModule_GetDef(mod));
@@ -1234,12 +1233,6 @@ fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
         }
     }
 
-    if (fix_up_extension_for_interpreter(
-                tstate, mod, def, name, modules) < 0)
-    {
-        return -1;
-    }
-
     return 0;
 }
 
@@ -1258,7 +1251,12 @@ _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
     }
 
     PyThreadState *tstate = _PyThreadState_GET();
-    if (fix_up_extension(tstate, mod, def, name, filename, modules) < 0) {
+    if (fix_up_extension(tstate, mod, def, name, filename) < 0) {
+        return -1;
+    }
+    if (fix_up_extension_for_interpreter(
+                tstate, mod, def, name, modules) < 0)
+    {
         return -1;
     }
     return 0;
@@ -1391,7 +1389,12 @@ _PyImport_FixupBuiltin(PyThreadState *tstate, PyObject *mod, const char *name,
         goto finally;
     }
 
-    if (fix_up_extension(tstate, mod, def, nameobj, nameobj, modules) < 0) {
+    if (fix_up_extension(tstate, mod, def, nameobj, nameobj) < 0) {
+        goto finally;
+    }
+    if (fix_up_extension_for_interpreter(
+                tstate, mod, def, nameobj, modules) < 0)
+    {
         goto finally;
     }
 
@@ -1464,8 +1467,13 @@ create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
         /* Remember pointer to module init function. */
         def->m_base.m_init = p0;
 
+        if (fix_up_extension(tstate, mod, def, name, name) < 0) {
+            return NULL;
+        }
         PyObject *modules = get_modules_dict(tstate, true);
-        if (fix_up_extension(tstate, mod, def, name, name, modules) < 0) {
+        if (fix_up_extension_for_interpreter(
+                    tstate, mod, def, name, modules) < 0)
+        {
             return NULL;
         }
         return mod;

From f347f8d0fb0c6857f73d87fda573e110ebf5c589 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Tue, 23 Apr 2024 08:54:07 -0600
Subject: [PATCH 08/11] fix_up_extension_for_interpreter() ->
 finish_singlephase_extension()

---
 Python/import.c | 55 +++++++++++++++++++++++--------------------------
 1 file changed, 26 insertions(+), 29 deletions(-)

diff --git a/Python/import.c b/Python/import.c
index cfc70498d1cfad..e762870b7344b4 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1171,26 +1171,6 @@ is_core_module(PyInterpreterState *interp, PyObject *name, PyObject *path)
     return 0;
 }
 
-static int
-fix_up_extension_for_interpreter(PyThreadState *tstate,
-                                 PyObject *mod, PyModuleDef *def,
-                                 PyObject *name, PyObject *modules)
-{
-    assert(mod != NULL && PyModule_Check(mod));
-    assert(def == PyModule_GetDef(mod));
-
-    if (_modules_by_index_set(tstate->interp, def, mod) < 0) {
-        return -1;
-    }
-
-    if (modules != NULL) {
-        if (PyObject_SetItem(modules, name, mod) < 0) {
-            return -1;
-        }
-    }
-
-    return 0;
-}
 
 static int
 fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
@@ -1236,6 +1216,29 @@ fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
     return 0;
 }
 
+/* For multi-phase init modules, the module is finished
+ * by PyModule_FromDefAndSpec(). */
+static int
+finish_singlephase_extension(PyThreadState *tstate,
+                             PyObject *mod, PyModuleDef *def,
+                             PyObject *name, PyObject *modules)
+{
+    assert(mod != NULL && PyModule_Check(mod));
+    assert(def == PyModule_GetDef(mod));
+
+    if (_modules_by_index_set(tstate->interp, def, mod) < 0) {
+        return -1;
+    }
+
+    if (modules != NULL) {
+        if (PyObject_SetItem(modules, name, mod) < 0) {
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
 int
 _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
                                PyObject *filename, PyObject *modules)
@@ -1254,9 +1257,7 @@ _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
     if (fix_up_extension(tstate, mod, def, name, filename) < 0) {
         return -1;
     }
-    if (fix_up_extension_for_interpreter(
-                tstate, mod, def, name, modules) < 0)
-    {
+    if (finish_singlephase_extension(tstate, mod, def, name, modules) < 0) {
         return -1;
     }
     return 0;
@@ -1392,9 +1393,7 @@ _PyImport_FixupBuiltin(PyThreadState *tstate, PyObject *mod, const char *name,
     if (fix_up_extension(tstate, mod, def, nameobj, nameobj) < 0) {
         goto finally;
     }
-    if (fix_up_extension_for_interpreter(
-                tstate, mod, def, nameobj, modules) < 0)
-    {
+    if (finish_singlephase_extension(tstate, mod, def, nameobj, modules) < 0) {
         goto finally;
     }
 
@@ -1471,9 +1470,7 @@ create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
             return NULL;
         }
         PyObject *modules = get_modules_dict(tstate, true);
-        if (fix_up_extension_for_interpreter(
-                    tstate, mod, def, name, modules) < 0)
-        {
+        if (finish_singlephase_extension(tstate, mod, def, name, modules) < 0) {
             return NULL;
         }
         return mod;

From 49760890beec60dff8b07485d36ca33bfb982387 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Tue, 23 Apr 2024 09:40:52 -0600
Subject: [PATCH 09/11] fix_up_extension() ->
 update_global_state_for_extension()

---
 Python/import.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/Python/import.c b/Python/import.c
index e762870b7344b4..5331657a9bf34d 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1173,8 +1173,9 @@ is_core_module(PyInterpreterState *interp, PyObject *name, PyObject *path)
 
 
 static int
-fix_up_extension(PyThreadState *tstate, PyObject *mod, PyModuleDef *def,
-                 PyObject *name, PyObject *path)
+update_global_state_for_extension(PyThreadState *tstate,
+                                  PyObject *mod, PyModuleDef *def,
+                                  PyObject *name, PyObject *path)
 {
     assert(mod != NULL && PyModule_Check(mod));
     assert(def == _PyModule_GetDef(mod));
@@ -1254,7 +1255,9 @@ _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
     }
 
     PyThreadState *tstate = _PyThreadState_GET();
-    if (fix_up_extension(tstate, mod, def, name, filename) < 0) {
+    if (update_global_state_for_extension(
+            tstate, mod, def, name, filename) < 0)
+    {
         return -1;
     }
     if (finish_singlephase_extension(tstate, mod, def, name, modules) < 0) {
@@ -1390,7 +1393,9 @@ _PyImport_FixupBuiltin(PyThreadState *tstate, PyObject *mod, const char *name,
         goto finally;
     }
 
-    if (fix_up_extension(tstate, mod, def, nameobj, nameobj) < 0) {
+    if (update_global_state_for_extension(
+            tstate, mod, def, nameobj, nameobj) < 0)
+    {
         goto finally;
     }
     if (finish_singlephase_extension(tstate, mod, def, nameobj, modules) < 0) {
@@ -1466,7 +1471,9 @@ create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
         /* Remember pointer to module init function. */
         def->m_base.m_init = p0;
 
-        if (fix_up_extension(tstate, mod, def, name, name) < 0) {
+        if (update_global_state_for_extension(
+                tstate, mod, def, name, name) < 0)
+        {
             return NULL;
         }
         PyObject *modules = get_modules_dict(tstate, true);

From 5627ad973164a25e2308b55c4139a41060db3a6d Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Tue, 23 Apr 2024 11:24:58 -0600
Subject: [PATCH 10/11] Update the comment about extensions.

---
 Python/import.c | 104 +++++++++++++++++++++++++++---------------------
 1 file changed, 59 insertions(+), 45 deletions(-)

diff --git a/Python/import.c b/Python/import.c
index 5331657a9bf34d..c1162ac88956f3 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -631,77 +631,91 @@ _PyImport_ClearModulesByIndex(PyInterpreterState *interp)
     ...for single-phase init modules, where m_size == -1:
 
     (6). first time  (not found in _PyRuntime.imports.extensions):
-       1.  _imp_create_dynamic_impl() -> import_find_extension()
-       2.  _imp_create_dynamic_impl() -> _PyImport_LoadDynamicModuleWithSpec()
-       3.    _PyImport_LoadDynamicModuleWithSpec():  load <module init func>
-       4.    _PyImport_LoadDynamicModuleWithSpec():  call <module init func>
-       5.      <module init func> -> PyModule_Create() -> PyModule_Create2() -> PyModule_CreateInitialized()
-       6.        PyModule_CreateInitialized() -> PyModule_New()
-       7.        PyModule_CreateInitialized():  allocate mod->md_state
-       8.        PyModule_CreateInitialized() -> PyModule_AddFunctions()
-       9.        PyModule_CreateInitialized() -> PyModule_SetDocString()
-       10.       PyModule_CreateInitialized():  set mod->md_def
-       11.     <module init func>:  initialize the module
-       12.   _PyImport_LoadDynamicModuleWithSpec() -> _PyImport_CheckSubinterpIncompatibleExtensionAllowed()
-       13.   _PyImport_LoadDynamicModuleWithSpec():  set def->m_base.m_init
-       14.   _PyImport_LoadDynamicModuleWithSpec():  set __file__
-       15.   _PyImport_LoadDynamicModuleWithSpec() -> _PyImport_FixupExtensionObject()
-       16.     _PyImport_FixupExtensionObject():  add it to interp->imports.modules_by_index
-       17.     _PyImport_FixupExtensionObject():  copy __dict__ into def->m_base.m_copy
-       18.     _PyImport_FixupExtensionObject():  add it to _PyRuntime.imports.extensions
+       A. _imp_create_dynamic_impl() -> import_find_extension()
+       B. _imp_create_dynamic_impl() -> _PyImport_LoadDynamicModuleWithSpec()
+       C.   _PyImport_LoadDynamicModuleWithSpec():  load <module init func>
+       D.   _PyImport_LoadDynamicModuleWithSpec():  call <module init func>
+       E.     <module init func> -> PyModule_Create() -> PyModule_Create2()
+                                        -> PyModule_CreateInitialized()
+       F.       PyModule_CreateInitialized() -> PyModule_New()
+       G.       PyModule_CreateInitialized():  allocate mod->md_state
+       H.       PyModule_CreateInitialized() -> PyModule_AddFunctions()
+       I.       PyModule_CreateInitialized() -> PyModule_SetDocString()
+       J.     PyModule_CreateInitialized():  set mod->md_def
+       K.     <module init func>:  initialize the module, etc.
+       L.   _PyImport_LoadDynamicModuleWithSpec()
+                -> _PyImport_CheckSubinterpIncompatibleExtensionAllowed()
+       M.   _PyImport_LoadDynamicModuleWithSpec():  set def->m_base.m_init
+       N.   _PyImport_LoadDynamicModuleWithSpec() -> _PyImport_FixupExtensionObject()
+       O.     _PyImport_FixupExtensionObject() -> update_global_state_for_extension()
+       P.       update_global_state_for_extension():
+                        copy __dict__ into def->m_base.m_copy
+       Q.       update_global_state_for_extension():
+                        add it to _PyRuntime.imports.extensions
+       R.       _PyImport_FixupExtensionObject() -> finish_singlephase_extension()
+       S.         finish_singlephase_extension():
+                          add it to interp->imports.modules_by_index
+       T.         finish_singlephase_extension():  add it to sys.modules
+       U. _imp_create_dynamic_impl():  set __file__
+
+       Step (P) is skipped for core modules (sys/builtins).
 
     (6). subsequent times  (found in _PyRuntime.imports.extensions):
-       1. _imp_create_dynamic_impl() -> import_find_extension()
-       2.   import_find_extension() -> import_add_module()
-       3.     if name in sys.modules:  use that module
-       4.     else:
+       A. _imp_create_dynamic_impl() -> import_find_extension()
+       B.   import_find_extension() -> import_add_module()
+       C.     if name in sys.modules:  use that module
+       D.     else:
                 1. import_add_module() -> PyModule_NewObject()
                 2. import_add_module():  set it on sys.modules
-       5.   import_find_extension():  copy the "m_copy" dict into __dict__
-       6. _imp_create_dynamic_impl() -> _PyImport_CheckSubinterpIncompatibleExtensionAllowed()
+       E.   import_find_extension():  copy the "m_copy" dict into __dict__
+       F. _imp_create_dynamic_impl()
+                -> _PyImport_CheckSubinterpIncompatibleExtensionAllowed()
 
     (10). (every time):
-       1. noop
+       A. noop
 
 
     ...for single-phase init modules, where m_size >= 0:
 
     (6). not main interpreter and never loaded there - every time  (not found in _PyRuntime.imports.extensions):
-       1-16. (same as for m_size == -1)
+       A-N. (same as for m_size == -1)
+       O-Q. (skipped)
+       R-U. (same as for m_size == -1)
 
     (6). main interpreter - first time  (not found in _PyRuntime.imports.extensions):
-       1-16. (same as for m_size == -1)
-       17.     _PyImport_FixupExtensionObject():  add it to _PyRuntime.imports.extensions
+       A-O. (same as for m_size == -1)
+       P. (skipped)
+       Q-U. (same as for m_size == -1)
 
     (6). previously loaded in main interpreter  (found in _PyRuntime.imports.extensions):
-       1. _imp_create_dynamic_impl() -> import_find_extension()
-       2.   import_find_extension():  call def->m_base.m_init
-       3.   import_find_extension():  add the module to sys.modules
+       A. _imp_create_dynamic_impl() -> import_find_extension()
+       B.   import_find_extension():  call def->m_base.m_init
+       C.   import_find_extension():  add the module to sys.modules
 
     (10). every time:
-       1. noop
+       A. noop
 
 
     ...for multi-phase init modules:
 
     (6). every time:
-       1.  _imp_create_dynamic_impl() -> import_find_extension()  (not found)
-       2.  _imp_create_dynamic_impl() -> _PyImport_LoadDynamicModuleWithSpec()
-       3.    _PyImport_LoadDynamicModuleWithSpec():  load module init func
-       4.    _PyImport_LoadDynamicModuleWithSpec():  call module init func
-       5.    _PyImport_LoadDynamicModuleWithSpec() -> PyModule_FromDefAndSpec()
-       6.      PyModule_FromDefAndSpec(): gather/check moduledef slots
-       7.      if there's a Py_mod_create slot:
+       A.  _imp_create_dynamic_impl() -> import_find_extension()  (not found)
+       B.  _imp_create_dynamic_impl() -> _PyImport_LoadDynamicModuleWithSpec()
+       C.    _PyImport_LoadDynamicModuleWithSpec():  load module init func
+       D.    _PyImport_LoadDynamicModuleWithSpec():  call module init func
+       E.    _PyImport_LoadDynamicModuleWithSpec() -> PyModule_FromDefAndSpec()
+       F.      PyModule_FromDefAndSpec(): gather/check moduledef slots
+       G.      if there's a Py_mod_create slot:
                  1. PyModule_FromDefAndSpec():  call its function
-       8.      else:
+       H.      else:
                  1. PyModule_FromDefAndSpec() -> PyModule_NewObject()
-       9:      PyModule_FromDefAndSpec():  set mod->md_def
-       10.     PyModule_FromDefAndSpec() -> _add_methods_to_object()
-       11.     PyModule_FromDefAndSpec() -> PyModule_SetDocString()
+       I:      PyModule_FromDefAndSpec():  set mod->md_def
+       J.      PyModule_FromDefAndSpec() -> _add_methods_to_object()
+       K.      PyModule_FromDefAndSpec() -> PyModule_SetDocString()
 
     (10). every time:
-       1. _imp_exec_dynamic_impl() -> exec_builtin_or_dynamic()
-       2.   if mod->md_state == NULL (including if m_size == 0):
+       A. _imp_exec_dynamic_impl() -> exec_builtin_or_dynamic()
+       B.   if mod->md_state == NULL (including if m_size == 0):
             1. exec_builtin_or_dynamic() -> PyModule_ExecDef()
             2.   PyModule_ExecDef():  allocate mod->md_state
             3.   if there's a Py_mod_exec slot:

From 8b4e216dfa45d84eae952ddde4010908adb9220f Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Tue, 23 Apr 2024 11:30:24 -0600
Subject: [PATCH 11/11] Make sure __file__ is set before m_copy gets populated.

---
 Python/import.c   | 6 ------
 Python/importdl.c | 5 +++++
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/Python/import.c b/Python/import.c
index c1162ac88956f3..30d8082607ab37 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -3848,12 +3848,6 @@ _imp_create_dynamic_impl(PyObject *module, PyObject *spec, PyObject *file)
     }
 
     mod = _PyImport_LoadDynamicModuleWithSpec(spec, fp);
-    if (mod != NULL) {
-        /* Remember the filename as the __file__ attribute */
-        if (PyModule_AddObjectRef(mod, "__file__", filename) < 0) {
-            PyErr_Clear(); /* Not important enough to report */
-        }
-    }
 
     // XXX Shouldn't this happen in the error cases too.
     if (fp) {
diff --git a/Python/importdl.c b/Python/importdl.c
index 7cf30bea3a861a..e512161d3071f2 100644
--- a/Python/importdl.c
+++ b/Python/importdl.c
@@ -226,6 +226,11 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp)
     }
     def->m_base.m_init = p0;
 
+    /* Remember the filename as the __file__ attribute */
+    if (PyModule_AddObjectRef(m, "__file__", filename) < 0) {
+        PyErr_Clear(); /* Not important enough to report */
+    }
+
     PyObject *modules = PyImport_GetModuleDict();
     if (_PyImport_FixupExtensionObject(m, name_unicode, filename, modules) < 0)
         goto error;