[issue42035] [C API] PyType_GetSlot cannot get tp_name

[Petr Viktorin]

Petr Viktorin <encukou at gmail.com> added the comment:

Sorry for the delay; getting 652 into Python 3.10 took up most of my time.


So, in the current proposal:
- `PyType_GetName(t)` is equivalent to `PyObject_GetAttrString(t, "__name__")`
- for the qualified name you can use `PyObject_GetAttrString(t, "__qualname__")`
- there is still no way to get t.tp_name

The advantage of PyType_GetName over a regular getattr is that it's fast for heap types (there's no dict lookup, and the string object is cached as ht_name). For static types, it's a bit slower (a string object needs to be built, but still there's no dict lookup).

If we go this way, why not add PyType_GetQualName as well?

(Is the speed, compared to getattr, worth adding two new functions? I guess it is, barely.)

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The OP specifically requested a way to get tp_name, which the current PR does not do. I don't think it should, either:
- there's no way to assure that `char* tp_name` is not deallocated before the caller is done with it (especially considering that other Python implementations should be able to implement the stable ABI, and those shouldn't need store tp_name as char*).
- there is already __name__ and __qualname__ (and __module__); tp_name is a weird mix that I, personally, won't miss if it goes away. I think it's OK to only use it for creation (as PyType_Spec.name), and then expose the __name__/__module__ derived from it. It's not how CPython works, but that's OK for the limited API.

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