Issue #28123: _PyDict_GetItem_KnownHash() now can raise an exception as

PyDict_GetItemWithError().  Patch by Xiang Zhang.

Lib/test/test_dict.py

@@ -1055,6 +1055,37 @@ class DictTest(unittest.TestCase):
         support.check_free_after_iterating(self, lambda d: iter(d.values()), dict)
         support.check_free_after_iterating(self, lambda d: iter(d.items()), dict)
 
+
+class CAPITest(unittest.TestCase):
+
+    # Test _PyDict_GetItem_KnownHash()
+    @support.cpython_only
+    def test_getitem_knownhash(self):
+        from _testcapi import dict_getitem_knownhash
+
+        d = {'x': 1, 'y': 2, 'z': 3}
+        self.assertEqual(dict_getitem_knownhash(d, 'x', hash('x')), 1)
+        self.assertEqual(dict_getitem_knownhash(d, 'y', hash('y')), 2)
+        self.assertEqual(dict_getitem_knownhash(d, 'z', hash('z')), 3)
+
+        # not a dict
+        self.assertRaises(SystemError, dict_getitem_knownhash, [], 1, hash(1))
+        # key does not exist
+        self.assertRaises(KeyError, dict_getitem_knownhash, {}, 1, hash(1))
+
+        class Exc(Exception): pass
+        class BadEq:
+            def __eq__(self, other):
+                raise Exc
+            def __hash__(self):
+                return 7
+
+        k1, k2 = BadEq(), BadEq()
+        d = {k1: 1}
+        self.assertEqual(dict_getitem_knownhash(d, k1, hash(k1)), 1)
+        self.assertRaises(Exc, dict_getitem_knownhash, d, k2, hash(k2))
+
+
 from test import mapping_tests
 
 class GeneralMappingTests(mapping_tests.BasicTestMappingProtocol):

Modules/_collectionsmodule.c

@@ -2300,6 +2300,8 @@ _count_elements(PyObject *self, PyObject *args)
 
             oldval = _PyDict_GetItem_KnownHash(mapping, key, hash);
             if (oldval == NULL) {
+                if (PyErr_Occurred())
+                    goto done;
                 if (_PyDict_SetItem_KnownHash(mapping, key, one, hash) < 0)
                     goto done;
             } else {

Modules/_testcapimodule.c

@@ -238,6 +238,26 @@ test_dict_iteration(PyObject* self)
     return Py_None;
 }
 
+static PyObject*
+dict_getitem_knownhash(PyObject *self, PyObject *args)
+{
+    PyObject *mp, *key, *result;
+    Py_ssize_t hash;
+
+    if (!PyArg_ParseTuple(args, "OOn:dict_getitem_knownhash",
+                          &mp, &key, &hash)) {
+        return NULL;
+    }
+
+    result = _PyDict_GetItem_KnownHash(mp, key, (Py_hash_t)hash);
+    if (result == NULL && !PyErr_Occurred()) {
+        _PyErr_SetKeyError(key);
+        return NULL;
+    }
+
+    Py_XINCREF(result);
+    return result;
+}
 
 /* Issue #4701: Check that PyObject_Hash implicitly calls
  *   PyType_Ready if it hasn't already been called
@@ -4003,6 +4023,7 @@ static PyMethodDef TestMethods[] = {
     {"test_datetime_capi",  test_datetime_capi,              METH_NOARGS},
     {"test_list_api",           (PyCFunction)test_list_api,      METH_NOARGS},
     {"test_dict_iteration",     (PyCFunction)test_dict_iteration,METH_NOARGS},
+    {"dict_getitem_knownhash",  dict_getitem_knownhash,          METH_VARARGS},
     {"test_lazy_hash_inheritance",      (PyCFunction)test_lazy_hash_inheritance,METH_NOARGS},
     {"test_long_api",           (PyCFunction)test_long_api,      METH_NOARGS},
     {"test_xincref_doesnt_leak",(PyCFunction)test_xincref_doesnt_leak,      METH_NOARGS},

Objects/dictobject.c

@@ -723,8 +723,10 @@ top:
             Py_INCREF(startkey);
             cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
             Py_DECREF(startkey);
-            if (cmp < 0)
+            if (cmp < 0) {
+                *value_addr = NULL;
                 return DKIX_ERROR;
+            }
             if (dk == mp->ma_keys && ep->me_key == startkey) {
                 if (cmp > 0) {
                     *value_addr = &ep->me_value;
@@ -1424,39 +1426,25 @@ PyDict_GetItem(PyObject *op, PyObject *key)
     return *value_addr;
 }
 
+/* Same as PyDict_GetItemWithError() but with hash supplied by caller.
+   This returns NULL *with* an exception set if an exception occurred.
+   It returns NULL *without* an exception set if the key wasn't present.
+*/
 PyObject *
 _PyDict_GetItem_KnownHash(PyObject *op, PyObject *key, Py_hash_t hash)
 {
     Py_ssize_t ix;
     PyDictObject *mp = (PyDictObject *)op;
-    PyThreadState *tstate;
     PyObject **value_addr;
 
-    if (!PyDict_Check(op))
+    if (!PyDict_Check(op)) {
+        PyErr_BadInternalCall();
         return NULL;
-
-    /* We can arrive here with a NULL tstate during initialization: try
-       running "python -Wi" for an example related to string interning.
-       Let's just hope that no exception occurs then...  This must be
-       _PyThreadState_Current and not PyThreadState_GET() because in debug
-       mode, the latter complains if tstate is NULL. */
-    tstate = _PyThreadState_UncheckedGet();
-    if (tstate != NULL && tstate->curexc_type != NULL) {
-        /* preserve the existing exception */
-        PyObject *err_type, *err_value, *err_tb;
-        PyErr_Fetch(&err_type, &err_value, &err_tb);
-        ix = (mp->ma_keys->dk_lookup)(mp, key, hash, &value_addr, NULL);
-        /* ignore errors */
-        PyErr_Restore(err_type, err_value, err_tb);
-        if (ix == DKIX_EMPTY)
-            return NULL;
     }
-    else {
-        ix = (mp->ma_keys->dk_lookup)(mp, key, hash, &value_addr, NULL);
-        if (ix == DKIX_EMPTY) {
-            PyErr_Clear();
-            return NULL;
-        }
+
+    ix = (mp->ma_keys->dk_lookup)(mp, key, hash, &value_addr, NULL);
+    if (ix < 0) {
+        return NULL;
     }
     return *value_addr;
 }
@@ -2431,8 +2419,16 @@ dict_merge(PyObject *a, PyObject *b, int override)
                 int err = 0;
                 Py_INCREF(key);
                 Py_INCREF(value);
-                if (override == 1 || _PyDict_GetItem_KnownHash(a, key, hash) == NULL)
+                if (override == 1)
+                    err = insertdict(mp, key, hash, value);
+                else if (_PyDict_GetItem_KnownHash(a, key, hash) == NULL) {
+                    if (PyErr_Occurred()) {
+                        Py_DECREF(value);
+                        Py_DECREF(key);
+                        return -1;
+                    }
                     err = insertdict(mp, key, hash, value);
+                }
                 else if (override != 0) {
                     _PyErr_SetKeyError(key);
                     Py_DECREF(value);