Sync pre-release CPython main branch from GitHub (2026-08-22)

Summary:
Imported python/cpython `3.16.0a0` from upstream rev [`b062727`](https://www.github.com/python/cpython/commit/b062727097e997bcb900e11503d3248daac903da) (committed 2026-08-22 18:45:59+00:00).

# Commit Info

- Base: (`3.16.0a0`) - [`918fb3a`](https://www.github.com/python/cpython/commit/918fb3aec907baf8d9b6181570ff308529be16a3) (commit date: 2026-08-22 03:51:49+00:00)
- Imported: (`3.16.0a0`) - [`b062727`](https://www.github.com/python/cpython/commit/b062727097e997bcb900e11503d3248daac903da) (commit date: 2026-08-22 18:45:59+00:00)

# Noteworthy file changes

- Low-signal files (3 added) (NEWS.d, docs, .github)

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GJWGnSd-OwxZ3PIPAISkJ09wVXI-br0LAAAz

Differential Revision: D117103803

fbshipit-source-id: bdc8d465325b49d07dcecec5ae4d9c1daa784af1

Author: generatedunixname1734921407115435

.github/CODEOWNERS

@@ -620,6 +620,12 @@ Lib/test/test_unittest/testmock/ @cjw296
 # Weakref
 **/*weakref*                  @kumaraditya303
 
+# Zlib
+Doc/library/zlib.rst          @StanFromIreland
+Lib/compression/zlib.py       @StanFromIreland
+Lib/test/test_zlib.py         @StanFromIreland
+Modules/_zlibmodule.c         @StanFromIreland
+
 # Zipfile.Path
 Lib/test/test_zipfile/_path/  @jaraco
 Lib/zipfile/_path/            @jaraco

Doc/glossary.rst

@@ -509,7 +509,7 @@ Glossary
       A piece of syntax which can be evaluated to some value.  In other words,
       an expression is an accumulation of expression elements like literals,
       names, attribute access, operators or function calls which all return a
-      value.  In contrast to many other languages, not all language constructs
+      value.  Not all language constructs
       are expressions.  There are also :term:`statement`\s which cannot be used
       as expressions, such as :keyword:`while`.  Assignments are also statements,
       not expressions.

Lib/test/test_clinic.py

@@ -4981,6 +4981,18 @@ def test_kwds_with_pos_only(self):
         self.assertEqual(ac_tester.kwds_with_pos_only(1, 2, y='y', z='z'), (1, 2, kwds))
         self.assertEqual(ac_tester.kwds_with_pos_only(1, 2, **kwds), (1, 2, kwds))
 
+    def test_kwds_with_optional_pos_only(self):
+        with self.assertRaises(TypeError):
+            ac_tester.kwds_with_optional_pos_only()
+        with self.assertRaises(TypeError):
+            ac_tester.kwds_with_optional_pos_only(y='y')
+        self.assertEqual(ac_tester.kwds_with_optional_pos_only(1), (1, None, {}))
+        self.assertEqual(ac_tester.kwds_with_optional_pos_only(1, 2), (1, 2, {}))
+        self.assertEqual(ac_tester.kwds_with_optional_pos_only(1, y='y'),
+                         (1, None, {'y': 'y'}))
+        self.assertEqual(ac_tester.kwds_with_optional_pos_only(1, 2, y='y'),
+                         (1, 2, {'y': 'y'}))
+
     def test_kwds_with_stararg(self):
         self.assertEqual(ac_tester.kwds_with_stararg(), ((), {}))
         self.assertEqual(ac_tester.kwds_with_stararg(1, 2), ((1, 2), {}))

Lib/test/test_zlib.py

@@ -182,6 +182,9 @@ def test_combine_no_iv_invalid_length(self):
             self.assertNotEqual(invalid_res, checksum)
 
         self.assertRaises(TypeError, self.combine, 0, 0, "len")
+        self.assertRaises(ValueError, self.combine, 0, 0, -1)
+        self.assertRaises(OverflowError, self.combine, 0, 0, 2**1000)
+        self.assertRaises(OverflowError, self.combine, 0, 0, -2**1000)
 
     def test_combine_with_iv(self):
         for _ in range(self.N):

Misc/NEWS.d/next/Build/2026-08-20-17-41-11.gh-issue-155911.yL3z8q.rst

@@ -0,0 +1,2 @@
+Fix curses detection with libraries in ``LIBS`` and
+:option:`--without-curses`. Patch by Shamil Abdulaev.

Misc/NEWS.d/next/Library/2026-08-21-14-30-00.gh-issue-156180.Qz3Lv8.rst

@@ -0,0 +1,3 @@
+:func:`zlib.adler32_combine` and :func:`zlib.crc32_combine` now raise
+:exc:`ValueError` if the *len2* argument is negative, instead of returning
+rubbish or hanging indefinitely, respectively.

Misc/NEWS.d/next/Tools-Demos/2026-08-22-11-00-00.gh-issue-156219.Wq2nRt.rst

@@ -0,0 +1,2 @@
+Fix Argument Clinic generating code which reads an optional positional
+argument which was not passed, if the function has a ``**kwds`` parameter.

Modules/_testclinic.c

@@ -2474,6 +2474,23 @@ kwds_with_pos_only_impl(PyObject *module, PyObject *a, PyObject *b,
 }
 
 
+/*[clinic input]
+kwds_with_optional_pos_only
+    a: object
+    b: object = None
+    /
+    **kwds: dict
+[clinic start generated code]*/
+
+static PyObject *
+kwds_with_optional_pos_only_impl(PyObject *module, PyObject *a, PyObject *b,
+                                 PyObject *kwds)
+/*[clinic end generated code: output=25a8458f5acc1a07 input=0b18b9e1670904ec]*/
+{
+    return pack_arguments_newref(3, a, b, kwds);
+}
+
+
 /*[clinic input]
 kwds_with_stararg
     *args: tuple
@@ -2611,6 +2628,7 @@ static PyMethodDef tester_methods[] = {
 
     LONE_KWDS_METHODDEF
     KWDS_WITH_POS_ONLY_METHODDEF
+    KWDS_WITH_OPTIONAL_POS_ONLY_METHODDEF
     KWDS_WITH_STARARG_METHODDEF
     KWDS_WITH_POS_ONLY_AND_STARARG_METHODDEF
 

Modules/clinic/_testclinic_kwds.c.h

@@ -1948,7 +1948,10 @@ zlib_adler32_combine_impl(PyObject *module, unsigned int adler1,
 #else
     z_off_t len = convert_to_z_off_t(len2);
 #endif
-    if (PyErr_Occurred()) {
+    if (len < 0) {
+        if (!PyErr_Occurred()) {
+            PyErr_SetString(PyExc_ValueError, "len2 must be non-negative");
+        }
         return (unsigned int)-1;
     }
     return adler32_combine(adler1, adler2, len);
@@ -2033,7 +2036,10 @@ zlib_crc32_combine_impl(PyObject *module, unsigned int crc1,
 #else
     z_off_t len = convert_to_z_off_t(len2);
 #endif
-    if (PyErr_Occurred()) {
+    if (len < 0) {
+        if (!PyErr_Occurred()) {
+            PyErr_SetString(PyExc_ValueError, "len2 must be non-negative");
+        }
         return (unsigned int)-1;
     }
     return crc32_combine(crc1, crc2, len);