From 9e008fe3519b6c08edc2f2363bc2eb4a4e044698 Mon Sep 17 00:00:00 2001
From: "Miss Islington (bot)"
<31488909+miss-islington@users.noreply.github.com>
Date: Mon, 19 Sep 2022 04:48:58 -0700
Subject: [PATCH] gh-96821: Fix undefined behaviour in `_testcapimodule.c`
(GH-96915) (GH-96927)
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* gh-96821: Assert for demonstrating undefined behaviour
* Fix UB
(cherry picked from commit cbdeda8ce7a3543cb3376d70e4cd46fcf24f42a7)
Co-authored-by: C.A.M. Gerlach <CAM.Gerlach@Gerlach.CAM>
Co-authored-by: Matthias Görgens <matthias.goergens@gmail.com>
---
.../2022-09-18-08-47-40.gh-issue-96821.Co2iOq.rst | 1 +
Modules/_testcapimodule.c | 4 +++-
2 files changed, 4 insertions(+), 1 deletion(-)
create mode 100644 Misc/NEWS.d/next/Core and Builtins/2022-09-18-08-47-40.gh-issue-96821.Co2iOq.rst
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-09-18-08-47-40.gh-issue-96821.Co2iOq.rst b/Misc/NEWS.d/next/Core and Builtins/2022-09-18-08-47-40.gh-issue-96821.Co2iOq.rst
new file mode 100644
index 00000000000..4fd0532e827
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-09-18-08-47-40.gh-issue-96821.Co2iOq.rst
@@ -0,0 +1 @@
+Fix undefined behaviour in ``_testcapimodule.c``.
diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 1a3cbe0b212..43fec8138a0 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -5576,8 +5576,10 @@ meth_fastcall_keywords(PyObject* self, PyObject* const* args,
if (pyargs == NULL) {
return NULL;
}
+ assert(args != NULL || nargs == 0);
+ PyObject* const* args_offset = args == NULL ? NULL : args + nargs;
PyObject *pykwargs = PyObject_Vectorcall((PyObject*)&PyDict_Type,
- args + nargs, 0, kwargs);
+ args_offset, 0, kwargs);
return Py_BuildValue("NNN", _null_to_none(self), pyargs, pykwargs);
}
--
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