Issue #27809: PyEval_CallObjectWithKeywords() doesn't increment temporary the
reference counter of the args tuple (positional arguments). The caller already
holds a strong reference to it.
This was found by PVS-Studio:
V595 The 'def' pointer was utilized before it was verified
against nullptr. Check lines: 286, 292. pystate.c 286
Initial patch by Christian Heimes.
Issue #27128. When a Python function is called with no arguments, but all
parameters have a default value: use default values as arguments for the fast
path.
Issue #27128: Modify PyEval_CallObjectWithKeywords() to use
_PyObject_FastCall() when args==NULL and kw==NULL. It avoids the creation of a
temporary empty tuple for positional arguments.
Issue #27128: Add _PyObject_FastCall(), a new calling convention avoiding a
temporary tuple to pass positional parameters in most cases, but create a
temporary tuple if needed (ex: for the tp_call slot).
The API is prepared to support keyword parameters, but the full implementation
will come later (_PyFunction_FastCall() doesn't support keyword parameters
yet).
Add also:
* _PyStack_AsTuple() helper function: convert a "stack" of parameters to
a tuple.
* _PyCFunction_FastCall(): fast call implementation for C functions
* _PyFunction_FastCall(): fast call implementation for Python functions
