gh-118702: Implement vectorcall for BaseException (#118703)

* BaseException_vectorcall() now creates a tuple from 'args' array.
* Creation an exception using BaseException_vectorcall() is now a
  single function call, rather than having to call
  BaseException_new() and then BaseException_init().
  Calling BaseException_init() is inefficient since it overrides
  the 'args' attribute.
* _PyErr_SetKeyError() now uses PyObject_CallOneArg() to create the
  KeyError instance to use BaseException_vectorcall().

1 files changed, 5 insertions, 4 deletions

diff --git a/Python/errors.c b/Python/errors.c
index 433253b..ad6b7db 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -257,13 +257,14 @@ void
 _PyErr_SetKeyError(PyObject *arg)
 {
     PyThreadState *tstate = _PyThreadState_GET();
-    PyObject *tup = PyTuple_Pack(1, arg);
-    if (!tup) {
+    PyObject *exc = PyObject_CallOneArg(PyExc_KeyError, arg);
+    if (!exc) {
         /* caller will expect error to be set anyway */
         return;
     }
-    _PyErr_SetObject(tstate, PyExc_KeyError, tup);
-    Py_DECREF(tup);
+
+    _PyErr_SetObject(tstate, (PyObject*)Py_TYPE(exc), exc);
+    Py_DECREF(exc);
 }
 
 void