On 2018-07-31 12:10, INADA Naoki wrote:
Surely, they should understand they must use CCALL_* flags instead of METH_* flags when implementing fast-callable object.
Yes indeed. But implementing a fast-callable object is quite specialized, not something that ordinary extension writers would care about. And if they don't care about performance, tp_call remains supported.
More generally: with PEP 580, everything from the documented C API remains supported. So people can write extensions exactly as before. They only need to care about PEP 580 if they want to use the new features that PEP 580 adds (or if they used undocumented internals).