I agree that this would be cool. There is a tiny bit of a backwards compatibility concern as the new function signature would be incompatible with anything we had before, but I would guess that any code that chooses to bypass PyObject_Call() & friends would at least fall back to using it if it finds flags that it cannot handle. Cython code definitely does and always did, but there might be bugs. This change is the perfect way to "find" those. ;-)

Anyway, Victor, I definitely appreciate your efforts in this direction.