gh-111489: Add PyTuple_FromArray() function

Doc/c-api/tuple.rst

@@ -42,8 +42,10 @@ Tuple Objects
    Create a tuple of *size* items and copy references from *array* to the new
    tuple.
 
-   * Return a new reference on success.
-   * Set an exception and return ``NULL`` on error.
+   *array* can be NULL if *size* is ``0``.
+
+   On success, return a new reference.
+   On error, set an exception and return ``NULL``.
 
    .. versionadded:: next
 

Lib/test/test_capi/test_tuple.py

@@ -62,6 +62,28 @@ def test_tuple_new(self):
         self.assertRaises(SystemError, tuple_new, PY_SSIZE_T_MIN)
         self.assertRaises(MemoryError, tuple_new, PY_SSIZE_T_MAX)
 
+    def test_tuple_fromarray(self):
+        # Test PyTuple_FromArray()
+        tuple_fromarray = _testcapi.tuple_fromarray
+
+        tup = tuple([i] for i in range(5))
+        copy = tuple_fromarray(tup)
+        self.assertEqual(copy, tup)
+
+        tup = ()
+        copy = tuple_fromarray(tup)
+        self.assertIs(copy, tup)
+
+        copy = tuple_fromarray(NULL, 0)
+        self.assertIs(copy, ())
+
+        with self.assertRaises(ValueError):
+            tuple_fromarray(NULL, -1)
+        with self.assertRaises(ValueError):
+            tuple_fromarray(NULL, PY_SSIZE_T_MIN)
+        with self.assertRaises(MemoryError):
+            tuple_fromarray(NULL, PY_SSIZE_T_MAX)
+
     def test_tuple_pack(self):
         # Test PyTuple_Pack()
         pack = _testlimitedcapi.tuple_pack
@@ -279,18 +301,6 @@ def my_iter():
         self.assertEqual(tuple(my_iter()), (TAG, *range(10)))
         self.assertEqual(tuples, [])
 
-    def test_tuple_fromarray(self):
-        # Test PyTuple_FromArray()
-        tuple_fromarray = _testcapi.tuple_fromarray
-
-        tup = tuple(object() for _ in range(5))
-        copy = tuple_fromarray(tup)
-        self.assertEqual(copy, tup)
-
-        tup = ()
-        copy = tuple_fromarray(tup)
-        self.assertIs(copy, tup)
-
 
 if __name__ == "__main__":
     unittest.main()

Modules/_testcapi/tuple.c

@@ -108,40 +108,26 @@ static PyObject *
 tuple_fromarray(PyObject* Py_UNUSED(module), PyObject *args)
 {
     PyObject *src;
-    if (!PyArg_ParseTuple(args, "O!", &PyTuple_Type, &src)) {
+    Py_ssize_t size = -1;
+    if (!PyArg_ParseTuple(args, "O|n", &src, &size)) {
         return NULL;
     }
-
-    Py_ssize_t size = PyTuple_GET_SIZE(src);
-    PyObject **array = PyMem_Malloc(size * sizeof(PyObject**));
-    if (array == NULL) {
-        PyErr_NoMemory();
+    if (src != Py_None && !PyTuple_Check(src)) {
+        PyErr_SetString(PyExc_TypeError, "expect a tuple");
         return NULL;
     }
-    for (Py_ssize_t i = 0; i < size; i++) {
-        array[i] = Py_NewRef(PyTuple_GET_ITEM(src, i));
-    }
-
-    PyObject *tuple = PyTuple_FromArray(array, size);
-    if (tuple == NULL) {
-        goto done;
-    }
-
-    for (Py_ssize_t i = 0; i < size; i++) {
-        // check that the array is not modified
-        assert(array[i] == PyTuple_GET_ITEM(src, i));
 
-        // check that the array was copied properly
-        assert(PyTuple_GET_ITEM(tuple, i) == array[i]);
+    PyObject **items;
+    if (src != Py_None) {
+        items = &PyTuple_GET_ITEM(src, 0);
+        if (size < 0) {
+            size = PyTuple_GET_SIZE(src);
+        }
     }
-
-done:
-    for (Py_ssize_t i = 0; i < size; i++) {
-        Py_DECREF(array[i]);
+    else {
+        items = NULL;
     }
-    PyMem_Free(array);
-
-    return tuple;
+    return PyTuple_FromArray(items, size);
 }
 
 

Objects/tupleobject.c

@@ -371,6 +371,10 @@ PyTuple_FromArray(PyObject *const *src, Py_ssize_t n)
     if (n == 0) {
         return tuple_get_empty();
     }
+    if (n < 0) {
+        PyErr_SetString(PyExc_ValueError, "size must be nonnegative");
+        return NULL;
+    }
 
     PyTupleObject *tuple = tuple_alloc(n);
     if (tuple == NULL) {