Em sex., 22 de abr. de 2022 às 09:02, Petr Viktorin <encukou@gmail.com> escreveu:
Hello Fabio, Let's talk a bit about which API should, exactly, be guaranteed to not change across minor releases. So far it looks like: - PyEval_RequestCodeExtraIndex - PyCode_GetExtra - PyCode_SetExtra - PyFrameEvalFunction - PyInterpreterState_GetEvalFrameFunc - PyInterpreterState_SetEvalFrameFunc
Do any more come to mind?
The issue with this set is that in 3.11, _PyFrameEvalFunction changes its signature to take _PyInterpreterFrame rather than PyFrameObject. Exposing _PyInterpreterFrame would be quite problematic. For example, since it's not a PyObject, it has its own lifetime management that's controlled by the interpreter itself,. And it includes several pointers whose lifetime and semantics also isn't guaranteed (they might be borrowed, cached or filled on demand). I don't think we can make any guarantees on these, so the info needs to be accessed using getter functions.
There is the function _PyFrame_GetFrameObject, which returns a PyFrameObject. I think it would be best to only expose _PyInterpreterFrame as an opaque structure, and expose PyFrame_GetFrameObject so debuggers can get a PyFrameObject from it. Does that sound reasonable?
Humm, now I'm a bit worried... the approach the debugger is using gets the PyFrameObject that's about to be executed and changes the PyFrameObject.f_code just before the execution so that the new code is executed instead. From what you're saying the PyFrameObject isn't really used anymore (apparently it's substituted by a _PyInterpreterFrame?)... in this case, will this approach still let the debugger patch the code object in the frame before it's actually executed? -- i.e.: the debugger changes the state.interp.eval_frame to its own custom evaluation function, but _PyEval_EvalFrameDefault is still what ends up being called afterwards (it works more as a hook to change the PyFrameObject.f_code prior to execution than as an alternate interpreter). On Thu, Mar 24, 2022 at 8:13 PM Fabio Zadrozny <fabiofz@gmail.com> wrote:
Em qui., 24 de mar. de 2022 às 15:39, Fabio Zadrozny <fabiofz@gmail.com>
PEP 523 API added more private functions for code objects:
* _PyEval_RequestCodeExtraIndex() * _PyCode_GetExtra() * _PyCode_SetExtra()
The _PyEval_RequestCodeExtraIndex() function seems to be used by the pydevd debugger. The two others seem to be unused in the wild. I'm not sure if these ones should be moved to the internal C API. They can be left unchanged, since they don't use a type only defined by the internal C API.
Just to note, the pydevd/debugpy debuggers actually uses all of those APIs.
i.e.:
https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd...
https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd...
https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd...
The debugger already has workarounds because of changes to evaluation
api over time (see: https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd...) and I know 3.11 won't be different.
I'm ok with changes as I understand that this is a special API -- as
long as there's still a way to use it and get the information needed (the debugger already goes through many hops because it needs to use many internals of CPython -- in every new release it's a **really** big task to update to the latest version as almost everything that the debugger relies to make debugging fast changes across versions and I never really know if it'll be possible to support it until I really try to do the port -- I appreciate having less things in a public API so it's easier to have extensions work in other interpreters/not recompiling on newer versions, but please keep it possible to use private APIs which provides the same access that CPython has to access things internally for special cases such as the debugger).
Maybe later on that PEP from mark which allows a better debugger API
could alleviate that (but until then, if possible I appreciate it if
Anyways, to wrap up, the debugger already needs to be built with
`Py_BUILD_CORE_MODULE=1` anyways, so, I guess having it in a private API (as long as it's still accessible in that case) is probably not a big issue for the debugger and having setters/getters to set it instead of relying on `state.interp.eval_frame` seems good to me.
Cheers,
Fabio
I think the main issue here is the compatibility across the same version
escreveu: there's some effort not to break things unless really needed -- ideally with instructions on how to port). though... is it possible to have some kind of guarantee on private APIs that something won't change across micro-releases?
I.e.: having the frame evaluation function change across major releases
and having them be reworked seems reasonable, but then having the frame evaluation be changed across micro-releases wouldn't be.
So, I'm ok in pushing things to the internal API, but then I still would
like guarantees about the compatibility of that API in the same major release (otherwise those setters/getters/frame evaluation should probably remain on the public API if the related structure was moved to the internal API).
Cheers,
Fabio _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-leave@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at
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