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/class...
That's better indeed.