bpo-28411: Support other mappings in PyInterpreterState.modules. (#3593)

The concrete PyDict_* API is used to interact with PyInterpreterState.modules in a number of places. This isn't compatible with all dict subclasses, nor with other Mapping implementations. This patch switches the concrete API usage to the corresponding abstract API calls.

We also add a PyImport_GetModule() function (and some other helpers) to reduce a bunch of code duplication.

1 files changed, 121 insertions, 43 deletions

diff --git a/Python/import.c b/Python/import.c
index 7aa7a1bdf7..5e841ca782 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -291,8 +291,9 @@ PyObject *
 PyImport_GetModuleDict(void)
 {
     PyInterpreterState *interp = PyThreadState_GET()->interp;
-    if (interp->modules == NULL)
+    if (interp->modules == NULL) {
         Py_FatalError("PyImport_GetModuleDict: no module dictionary!");
+    }
     return interp->modules;
 }
 
@@ -308,6 +309,55 @@ _PyImport_IsInitialized(PyInterpreterState *interp)
     return 1;
 }
 
+PyObject *
+_PyImport_GetModuleId(struct _Py_Identifier *nameid)
+{
+    PyObject *name = _PyUnicode_FromId(nameid); /* borrowed */
+    if (name == NULL) {
+        return NULL;
+    }
+    return PyImport_GetModule(name);
+}
+
+int
+_PyImport_SetModule(PyObject *name, PyObject *m)
+{
+    PyObject *modules = PyImport_GetModuleDict();
+    return PyObject_SetItem(modules, name, m);
+}
+
+int
+_PyImport_SetModuleString(const char *name, PyObject *m)
+{
+    PyObject *modules = PyImport_GetModuleDict();
+    return PyMapping_SetItemString(modules, name, m);
+}
+
+PyObject *
+PyImport_GetModule(PyObject *name)
+{
+    PyObject *m;
+    PyObject *modules = PyImport_GetModuleDict();
+    if (modules == NULL) {
+        PyErr_SetString(PyExc_RuntimeError, "unable to get sys.modules");
+        return NULL;
+    }
+    Py_INCREF(modules);
+    if (PyDict_CheckExact(modules)) {
+        m = PyDict_GetItemWithError(modules, name);  /* borrowed */
+        Py_XINCREF(m);
+    }
+    else {
+        m = PyObject_GetItem(modules, name);
+        if (PyErr_ExceptionMatches(PyExc_KeyError)) {
+            PyErr_Clear();
+        }
+    }
+    Py_DECREF(modules);
+    return m;
+}
+
+
 /* List of names to clear in sys */
 static const char * const sys_deletes[] = {
     "path", "argv", "ps1", "ps2",
@@ -387,21 +437,51 @@ PyImport_Cleanup(void)
         if (PyErr_Occurred()) \
             PyErr_Clear(); \
     }
+#define CLEAR_MODULE(name, mod) \
+    if (PyModule_Check(mod)) { \
+        if (Py_VerboseFlag && PyUnicode_Check(name)) \
+            PySys_FormatStderr("# cleanup[2] removing %U\n", name); \
+        STORE_MODULE_WEAKREF(name, mod); \
+        PyObject_SetItem(modules, name, Py_None); \
+    }
 
     /* Remove all modules from sys.modules, hoping that garbage collection
        can reclaim most of them. */
-    pos = 0;
-    while (PyDict_Next(modules, &pos, &key, &value)) {
-        if (PyModule_Check(value)) {
-            if (Py_VerboseFlag && PyUnicode_Check(key))
-                PySys_FormatStderr("# cleanup[2] removing %U\n", key);
-            STORE_MODULE_WEAKREF(key, value);
-            PyDict_SetItem(modules, key, Py_None);
+    if (PyDict_CheckExact(modules)) {
+        pos = 0;
+        while (PyDict_Next(modules, &pos, &key, &value)) {
+            CLEAR_MODULE(key, value);
+        }
+    }
+    else {
+        PyObject *iterator = PyObject_GetIter(modules);
+        if (iterator == NULL) {
+            PyErr_Clear();
+        }
+        else {
+            while ((key = PyIter_Next(iterator))) {
+                value = PyObject_GetItem(modules, key);
+                if (value == NULL) {
+                    PyErr_Clear();
+                    continue;
+                }
+                CLEAR_MODULE(key, value);
+                Py_DECREF(value);
+                Py_DECREF(key);
+            }
+            Py_DECREF(iterator);
         }
     }
 
     /* Clear the modules dict. */
-    PyDict_Clear(modules);
+    if (PyDict_CheckExact(modules)) {
+        PyDict_Clear(modules);
+    }
+    else {
+        _Py_IDENTIFIER(clear);
+        if (_PyObject_CallMethodId(modules, &PyId_clear, "") == NULL)
+            PyErr_Clear();
+    }
     /* Restore the original builtins dict, to ensure that any
        user data gets cleared. */
     dict = PyDict_Copy(interp->builtins);
@@ -541,10 +621,10 @@ _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
         PyErr_BadInternalCall();
         return -1;
     }
-    if (PyDict_SetItem(modules, name, mod) < 0)
+    if (PyObject_SetItem(modules, name, mod) < 0)
         return -1;
     if (_PyState_AddModule(mod, def) < 0) {
-        PyDict_DelItem(modules, name);
+        PyMapping_DelItem(modules, name);
         return -1;
     }
     if (def->m_size == -1) {
@@ -625,14 +705,14 @@ _PyImport_FindExtensionObjectEx(PyObject *name, PyObject *filename,
         mod = def->m_base.m_init();
         if (mod == NULL)
             return NULL;
-        if (PyDict_SetItem(modules, name, mod) == -1) {
+        if (PyObject_SetItem(modules, name, mod) == -1) {
             Py_DECREF(mod);
             return NULL;
         }
         Py_DECREF(mod);
     }
     if (_PyState_AddModule(mod, def) < 0) {
-        PyDict_DelItem(modules, name);
+        PyMapping_DelItem(modules, name);
         Py_DECREF(mod);
         return NULL;
     }
@@ -672,18 +752,27 @@ PyObject *
 _PyImport_AddModuleObject(PyObject *name, PyObject *modules)
 {
     PyObject *m;
-
-    if ((m = PyDict_GetItemWithError(modules, name)) != NULL &&
-        PyModule_Check(m)) {
-        return m;
+    if (PyDict_CheckExact(modules)) {
+        m = PyDict_GetItemWithError(modules, name);
+    }
+    else {
+        m = PyObject_GetItem(modules, name);
+        // For backward-comaptibility we copy the behavior
+        // of PyDict_GetItemWithError().
+        if (PyErr_ExceptionMatches(PyExc_KeyError)) {
+            PyErr_Clear();
+        }
     }
     if (PyErr_Occurred()) {
         return NULL;
     }
+    if (m != NULL && PyModule_Check(m)) {
+        return m;
+    }
     m = PyModule_NewObject(name);
     if (m == NULL)
         return NULL;
-    if (PyDict_SetItem(modules, name, m) != 0) {
+    if (PyObject_SetItem(modules, name, m) != 0) {
         Py_DECREF(m);
         return NULL;
     }
@@ -710,11 +799,13 @@ static void
 remove_module(PyObject *name)
 {
     PyObject *modules = PyImport_GetModuleDict();
-    if (PyDict_GetItem(modules, name) == NULL)
-        return;
-    if (PyDict_DelItem(modules, name) < 0)
+    if (PyMapping_DelItem(modules, name) < 0) {
+        if (!PyMapping_HasKey(modules, name)) {
+            return;
+        }
         Py_FatalError("import:  deleting existing key in"
                       "sys.modules failed");
+    }
 }
 
 
@@ -823,7 +914,6 @@ module_dict_for_exec(PyObject *name)
 static PyObject *
 exec_code_in_module(PyObject *name, PyObject *module_dict, PyObject *code_object)
 {
-    PyObject *modules = PyImport_GetModuleDict();
     PyObject *v, *m;
 
     v = PyEval_EvalCode(code_object, module_dict, module_dict);
@@ -833,15 +923,14 @@ exec_code_in_module(PyObject *name, PyObject *module_dict, PyObject *code_object
     }
     Py_DECREF(v);
 
-    if ((m = PyDict_GetItem(modules, name)) == NULL) {
+    m = PyImport_GetModule(name);
+    if (m == NULL) {
         PyErr_Format(PyExc_ImportError,
                      "Loaded module %R not found in sys.modules",
                      name);
         return NULL;
     }
 
-    Py_INCREF(m);
-
     return m;
 }
 
@@ -1540,8 +1629,7 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
         Py_INCREF(abs_name);
     }
 
-    PyObject *modules = PyImport_GetModuleDict();
-    mod = PyDict_GetItem(modules, abs_name);
+    mod = PyImport_GetModule(abs_name);
     if (mod != NULL && mod != Py_None) {
         _Py_IDENTIFIER(__spec__);
         _Py_IDENTIFIER(_initializing);
@@ -1550,7 +1638,6 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
         PyObject *spec;
         int initializing = 0;
 
-        Py_INCREF(mod);
         /* Optimization: only call _bootstrap._lock_unlock_module() if
            __spec__._initializing is true.
            NOTE: because of this, initializing must be set *before*
@@ -1579,6 +1666,7 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
         }
     }
     else {
+        Py_XDECREF(mod);
         mod = _PyObject_CallMethodIdObjArgs(interp->importlib,
                                             &PyId__find_and_load, abs_name,
                                             interp->import_func, NULL);
@@ -1628,8 +1716,7 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
                     goto error;
                 }
 
-                PyObject *modules = PyImport_GetModuleDict();
-                final_mod = PyDict_GetItem(modules, to_return);
+                final_mod = PyImport_GetModule(to_return);
                 Py_DECREF(to_return);
                 if (final_mod == NULL) {
                     PyErr_Format(PyExc_KeyError,
@@ -1637,7 +1724,6 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
                                  to_return);
                     goto error;
                 }
-                Py_INCREF(final_mod);
             }
         }
         else {
@@ -1682,19 +1768,16 @@ PyImport_ImportModuleLevel(const char *name, PyObject *globals, PyObject *locals
 PyObject *
 PyImport_ReloadModule(PyObject *m)
 {
+    _Py_IDENTIFIER(imp);
     _Py_IDENTIFIER(reload);
     PyObject *reloaded_module = NULL;
-    PyObject *modules = PyImport_GetModuleDict();
-    PyObject *imp = PyDict_GetItemString(modules, "imp");
+    PyObject *imp = _PyImport_GetModuleId(&PyId_imp);
     if (imp == NULL) {
         imp = PyImport_ImportModule("imp");
         if (imp == NULL) {
             return NULL;
         }
     }
-    else {
-        Py_INCREF(imp);
-    }
 
     reloaded_module = _PyObject_CallMethodIdObjArgs(imp, &PyId_reload, m, NULL);
     Py_DECREF(imp);
@@ -1720,7 +1803,6 @@ PyImport_Import(PyObject *module_name)
     PyObject *globals = NULL;
     PyObject *import = NULL;
     PyObject *builtins = NULL;
-    PyObject *modules = NULL;
     PyObject *r = NULL;
 
     /* Initialize constant string objects */
@@ -1775,12 +1857,8 @@ PyImport_Import(PyObject *module_name)
         goto err;
     Py_DECREF(r);
 
-    modules = PyImport_GetModuleDict();
-    r = PyDict_GetItemWithError(modules, module_name);
-    if (r != NULL) {
-        Py_INCREF(r);
-    }
-    else if (!PyErr_Occurred()) {
+    r = PyImport_GetModule(module_name);
+    if (r == NULL && !PyErr_Occurred()) {
         PyErr_SetObject(PyExc_KeyError, module_name);
     }