Merge branch 'main' into main

Author: jonathandung

Doc/c-api/file.rst

@@ -123,9 +123,12 @@ the :mod:`io` APIs instead.
 
    Write object *obj* to file object *p*.  The only supported flag for *flags* is
    :c:macro:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written
-   instead of the :func:`repr`.  Return ``0`` on success or ``-1`` on failure; the
-   appropriate exception will be set.
+   instead of the :func:`repr`.
+
+   If *obj* is ``NULL``, write the string ``"<NULL>"``.
 
+   Return ``0`` on success or ``-1`` on failure; the
+   appropriate exception will be set.
 
 .. c:function:: int PyFile_WriteString(const char *s, PyObject *p)
 

Doc/c-api/object.rst

@@ -363,6 +363,8 @@ Object Protocol
    representation on success, ``NULL`` on failure.  This is the equivalent of the
    Python expression ``repr(o)``.  Called by the :func:`repr` built-in function.
 
+   If argument is ``NULL``, return the string ``'<NULL>'``.
+
    .. versionchanged:: 3.4
       This function now includes a debug assertion to help ensure that it
       does not silently discard an active exception.
@@ -377,6 +379,8 @@ Object Protocol
    a string similar to that returned by :c:func:`PyObject_Repr` in Python 2.
    Called by the :func:`ascii` built-in function.
 
+   If argument is ``NULL``, return the string ``'<NULL>'``.
+
    .. index:: string; PyObject_Str (C function)
 
 
@@ -387,6 +391,8 @@ Object Protocol
    Python expression ``str(o)``.  Called by the :func:`str` built-in function
    and, therefore, by the :func:`print` function.
 
+   If argument is ``NULL``, return the string ``'<NULL>'``.
+
    .. versionchanged:: 3.4
       This function now includes a debug assertion to help ensure that it
       does not silently discard an active exception.
@@ -402,6 +408,8 @@ Object Protocol
    a TypeError is raised when *o* is an integer instead of a zero-initialized
    bytes object.
 
+   If argument is ``NULL``, return the :class:`bytes` object ``b'<NULL>'``.
+
 
 .. c:function:: int PyObject_IsSubclass(PyObject *derived, PyObject *cls)
 

Doc/c-api/unicode.rst

@@ -1867,7 +1867,7 @@ object.
    On success, return ``0``.
    On error, set an exception, leave the writer unchanged, and return ``-1``.
 
-.. c:function:: int PyUnicodeWriter_WriteUCS4(PyUnicodeWriter *writer, Py_UCS4 *str, Py_ssize_t size)
+.. c:function:: int PyUnicodeWriter_WriteUCS4(PyUnicodeWriter *writer, const Py_UCS4 *str, Py_ssize_t size)
 
    Writer the UCS4 string *str* into *writer*.
 
@@ -1887,6 +1887,8 @@ object.
 
    Call :c:func:`PyObject_Repr` on *obj* and write the output into *writer*.
 
+   If *obj* is ``NULL``, write the string ``"<NULL>"`` into *writer*.
+
    On success, return ``0``.
    On error, set an exception, leave the writer unchanged, and return ``-1``.
 

Include/cpython/unicodeobject.h

@@ -496,7 +496,7 @@ PyAPI_FUNC(int) PyUnicodeWriter_WriteWideChar(
     Py_ssize_t size);
 PyAPI_FUNC(int) PyUnicodeWriter_WriteUCS4(
     PyUnicodeWriter *writer,
-    Py_UCS4 *str,
+    const Py_UCS4 *str,
     Py_ssize_t size);
 
 PyAPI_FUNC(int) PyUnicodeWriter_WriteStr(

Lib/test/test_capi/test_list.py

@@ -350,6 +350,10 @@ def test_list_extend(self):
         # CRASHES list_extend(NULL, [])
         # CRASHES list_extend([], NULL)
 
+    def test_uninitialized_list_repr(self):
+        lst = _testlimitedcapi.list_new(3)
+        self.assertEqual(repr(lst), '[<NULL>, <NULL>, <NULL>]')
+
 
 if __name__ == "__main__":
     unittest.main()

Lib/test/test_capi/test_tuple.py

@@ -73,6 +73,7 @@ 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
@@ -357,6 +358,10 @@ def my_iter():
         self.assertEqual(tuple(my_iter()), (TAG, *range(10)))
         self.assertEqual(tuples, [])
 
+    def test_uninitialized_tuple_repr(self):
+        tup = _testlimitedcapi.tuple_new(3)
+        self.assertEqual(repr(tup), '(<NULL>, <NULL>, <NULL>)')
+
 
 if __name__ == "__main__":
     unittest.main()

Lib/test/test_capi/test_unicode.py

@@ -1779,6 +1779,13 @@ def test_basic(self):
         self.assertEqual(writer.finish(),
                          "var=long value 'repr'")
 
+    def test_repr_null(self):
+        writer = self.create_writer(0)
+        writer.write_utf8(b'var=', -1)
+        writer.write_repr(NULL)
+        self.assertEqual(writer.finish(),
+                         "var=<NULL>")
+
     def test_utf8(self):
         writer = self.create_writer(0)
         writer.write_utf8(b"ascii", -1)

Misc/NEWS.d/next/C_API/2026-03-18-20-18-59.gh-issue-146056.nnZIgp.rst

@@ -0,0 +1 @@
+:c:func:`PyUnicodeWriter_WriteRepr` now supports ``NULL`` argument.

Misc/NEWS.d/next/C_API/2026-03-18-23-44-29.gh-issue-146143.pwIrJq.rst

@@ -0,0 +1,2 @@
+:c:func:`PyUnicodeWriter_WriteUCS4` now accepts a pointer to a constant buffer
+of ``Py_UCS4``.

Misc/NEWS.d/next/Core_and_Builtins/2026-03-18-18-52-00.gh-issue-146056.r1tVSo.rst

@@ -0,0 +1 @@
+Fix :meth:`!list.__repr__` for lists containing ``NULL``\ s.