[Python-Dev] PEP 590 discussion

Jeroen Demeyer J.Demeyer at UGent.be
Mon Apr 15 04:38:11 EDT 2019


On 2019-04-14 13:30, Mark Shannon wrote:
> PY_VECTORCALL_ARGUMENTS_OFFSET exists so that callables that make onward
> calls with an additional argument can do so efficiently. The obvious
> example is bound-methods, but classes are at least as important.
> cls(*args) -> cls.new(cls, *args) -> cls.__init__(self, *args)

But tp_new and tp_init take the "cls" and "self" as separate arguments, 
not as part of *args. So I don't see why you need 
PY_VECTORCALL_ARGUMENTS_OFFSET for this.

> The updated minimal implementation now uses `const` arguments.
> Code that uses args[-1] must explicitly cast away the const.
> https://github.com/markshannon/cpython/blob/vectorcall-minimal/Objects/classobject.c#L55

That's better indeed.


Jeroen.


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