[Python-Dev] PEP 590: vectorcall without tp_call

[Jeroen Demeyer]

Hello,

I have one implementation question about vectorcall which is not 
specified in PEP 590: what should happen if a type implements vectorcall 
(i.e. _Py_TPFLAGS_HAVE_VECTORCALL is set) but doesn't set tp_call (i.e. 
tp_call == NULL)? I see the following possibilities:

1. Ignore this problem/assume that it won't happen. This would be bad, 
since callable(obj) would be False even though obj() would succeed.

2. Raise SystemError.

3. Automatically set tp_call to PyVectorcall_Call.

I would vote for 3 since it's the most user-friendly option. There is 
also no way how it could be wrong: it ensures that tp_call and 
vectorcall are consistent.

Any opinions?


Jeroen.