python · kmod · Aug 18, 2022 · vstinner · Aug 30, 2022
diff --git a/Include/internal/pycore_tuple.h b/Include/internal/pycore_tuple.h
@@ -67,6 +67,20 @@ struct _Py_tuple_state {
 extern PyObject *_PyTuple_FromArray(PyObject *const *, Py_ssize_t);
 extern PyObject *_PyTuple_FromArraySteal(PyObject *const *, Py_ssize_t);
 
+/* A faster, but unsafe, version of PyTuple_New for use in performance-
+ * critical paths.
+ *
+ * Zeroing the contents of a tuple is surprisingly expensive, so for
+ * cases where the contents of the tuple will immediately be overwritten,
+ * time can be saved by calling this non-zeroing version.
+ *
+ * This tuple is not safe to be seen by any other code since it will
+ * have garbage where PyObject pointers are expected. If there is any
+ * chance that the initialization code will raise an exception or do
+ * a GC collection, it is not safe to use this function.
+ */
+PyAPI_FUNC(PyObject *) _PyTuple_New_Nonzeroed(Py_ssize_t size);
+
 #ifdef __cplusplus
 }
 #endif

diff --git a/Modules/_json.c b/Modules/_json.c
@@ -353,7 +353,7 @@ _build_rval_index_tuple(PyObject *rval, Py_ssize_t idx) {
         Py_DECREF(rval);
         return NULL;
     }
-    tpl = PyTuple_New(2);
+    tpl = _PyTuple_New_Nonzeroed(2);
     if (tpl == NULL) {
         Py_DECREF(pyidx);
         Py_DECREF(rval);

@@ -4281,7 +4281,7 @@ dictiter_iternextitem(dictiterobject *di)
         }
     }
     else {
-        result = PyTuple_New(2);
+        result = _PyTuple_New_Nonzeroed(2);
         if (result == NULL)
             return NULL;
         PyTuple_SET_ITEM(result, 0, key);  /* steals reference */
@@ -4415,7 +4415,7 @@ dictreviter_iternext(dictiterobject *di)
             }
         }
         else {
-            result = PyTuple_New(2);
+            result = _PyTuple_New_Nonzeroed(2);
             if (result == NULL) {
                 return NULL;
             }

@@ -207,7 +207,7 @@ enum_next_long(enumobject *en, PyObject* next_item)
         }
         return result;
     }
-    result = PyTuple_New(2);
+    result = _PyTuple_New_Nonzeroed(2);
     if (result == NULL) {
         Py_DECREF(next_index);
         Py_DECREF(next_item);
@@ -257,7 +257,7 @@ enum_next(enumobject *en)
         }
         return result;
     }
-    result = PyTuple_New(2);
+    result = _PyTuple_New_Nonzeroed(2);
     if (result == NULL) {
         Py_DECREF(next_index);
         Py_DECREF(next_item);

diff --git a/Objects/longobject.c b/Objects/longobject.c
@@ -4249,7 +4249,7 @@ long_divmod(PyObject *a, PyObject *b)
     if (l_divmod((PyLongObject*)a, (PyLongObject*)b, &div, &mod) < 0) {
         return NULL;
     }
-    z = PyTuple_New(2);
+    z = _PyTuple_New_Nonzeroed(2);
     if (z != NULL) {
         PyTuple_SET_ITEM(z, 0, (PyObject *) div);
         PyTuple_SET_ITEM(z, 1, (PyObject *) mod);
@@ -5544,7 +5544,7 @@ _PyLong_DivmodNear(PyObject *a, PyObject *b)
             goto error;
     }
 
-    result = PyTuple_New(2);
+    result = _PyTuple_New_Nonzeroed(2);
     if (result == NULL)
         goto error;
 

diff --git a/Objects/odictobject.c b/Objects/odictobject.c
@@ -1770,7 +1770,7 @@ odictiter_iternext(odictiterobject *di)
         }
     }
     else {
-        result = PyTuple_New(2);
+        result = _PyTuple_New_Nonzeroed(2);
         if (result == NULL) {
             Py_DECREF(key);
             Py_DECREF(value);

diff --git a/Objects/stringlib/partition.h b/Objects/stringlib/partition.h
@@ -23,7 +23,7 @@ STRINGLIB(partition)(PyObject* str_obj,
         return NULL;
     }
 
-    out = PyTuple_New(3);
+    out = _PyTuple_New_Nonzeroed(3);
     if (!out)
         return NULL;
 
@@ -80,7 +80,7 @@ STRINGLIB(rpartition)(PyObject* str_obj,
         return NULL;
     }
 
-    out = PyTuple_New(3);
+    out = _PyTuple_New_Nonzeroed(3);
     if (!out)
         return NULL;
 

diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
@@ -83,6 +83,21 @@ PyTuple_New(Py_ssize_t size)
     return (PyObject *) op;
 }
 
+PyObject *
+_PyTuple_New_Nonzeroed(Py_ssize_t size)
+{
+    PyTupleObject *op;
+    if (size == 0) {
+        return tuple_get_empty();
+    }
+    op = tuple_alloc(size);
+    if (op == NULL) {
+        return NULL;
+    }
+    _PyObject_GC_TRACK(op);
+    return (PyObject *) op;
+}
+
 Py_ssize_t
 PyTuple_Size(PyObject *op)
 {

@@ -2051,7 +2051,7 @@ mro_implementation(PyTypeObject *type)
          */
         PyTypeObject *base = _PyType_CAST(PyTuple_GET_ITEM(bases, 0));
         Py_ssize_t k = PyTuple_GET_SIZE(base->tp_mro);
-        PyObject *result = PyTuple_New(k + 1);
+        PyObject *result = _PyTuple_New_Nonzeroed(k + 1);
         if (result == NULL) {
             return NULL;
         }
@@ -5639,7 +5639,7 @@ reduce_newobj(PyObject *obj)
             return NULL;
         }
         n = args ? PyTuple_GET_SIZE(args) : 0;
-        newargs = PyTuple_New(n+1);
+        newargs = _PyTuple_New_Nonzeroed(n+1);
         if (newargs == NULL) {
             Py_XDECREF(args);
             Py_DECREF(newobj);

@@ -2647,7 +2647,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
         }
 
         TARGET(BUILD_TUPLE) {
-            PyObject *tup = PyTuple_New(oparg);
+            PyObject *tup = _PyTuple_New_Nonzeroed(oparg);
             if (tup == NULL)
                 goto error;
             while (--oparg >= 0) {
@@ -5937,7 +5937,7 @@ PyEval_EvalCodeEx(PyObject *_co, PyObject *globals, PyObject *locals,
         allargs = args;
     }
     else {
-        kwnames = PyTuple_New(kwcount);
+        kwnames = _PyTuple_New_Nonzeroed(kwcount);
         if (kwnames == NULL) {
             goto fail;
         }