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Hi,

Update on this issue: I merged my 2 PRs.
https://bugs.python.org/issue46850

The following APIs have been moved to the internal C API:

- _PyFrameEvalFunction type
- _PyInterpreterState_GetEvalFrameFunc()
- _PyInterpreterState_SetEvalFrameFunc()
- _PyEval_EvalFrameDefault()

If you use any of these API in your debugger/profiler project, you
have do add something like the code below to your project:
---
#ifndef Py_BUILD_CORE_MODULE
# define Py_BUILD_CORE_MODULE
#endif
#include <Python.h>
#if PY_VERSION_HEX >= 0x030B00A7
# include <internal/pycore_interp.h> // _PyInterpreterState_SetEvalFrameFunc()
# include <internal/pycore_ceval.h> // _PyEval_EvalFrameDefault()
#endif
---

Contact me if you need help to update your affected projects.

IMO PEP 523 doesn't have to be updated since it already says that the
APIs are private.

Since these APIs were added by PEP 523, I documented these changes in
What's New in Python 3.11 > C API > Porting to Python 3.11,even if
these APIs are private.

Victor
--
Night gathers, and now my watch begins. It shall not end until my death.
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On 4/1/2022 10:01 AM, Victor Stinner wrote:
> Update on this issue: I merged my 2 PRs.
> https://bugs.python.org/issue46850

So what was the point of this discussion then?

I don't see any additional discussion on the bug, and the prevailing
opinion from actual users of this API is that it probably shouldn't
change, and certainly shouldn't become internal without additional
guarantees about stability.

Did we all just waste a whole lot of electrons discussing a foregone
conclusion?

(My apologies to the people I invited into this thread. I genuinely
thought it would help to have outside perspective on this potential change.)

Cheers,
Steve
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On 01. 04. 22 11:01, Victor Stinner wrote:
> Hi,
>
> Update on this issue: I merged my 2 PRs.
> https://bugs.python.org/issue46850
>
> The following APIs have been moved to the internal C API:
>
> - _PyFrameEvalFunction type
> - _PyInterpreterState_GetEvalFrameFunc()
> - _PyInterpreterState_SetEvalFrameFunc()
> - _PyEval_EvalFrameDefault()

Really?
I haven't seen any support for that in this thread or on the issue,
except from you.
Now, the people who'd like a non-breaking solution will now need rush to
develop and merge one until the next release, or the API breaks for
users and it'll be too late to do anything about it. Meanwhile, you're
off to make more changes. That is, frankly, very frustrating.

Could you please stop unilaterally breaking documented API?


> If you use any of these API in your debugger/profiler project, you
> have do add something like the code below to your project:
> ---
> #ifndef Py_BUILD_CORE_MODULE
> # define Py_BUILD_CORE_MODULE
> #endif
> #include <Python.h>
> #if PY_VERSION_HEX >= 0x030B00A7
> # include <internal/pycore_interp.h> // _PyInterpreterState_SetEvalFrameFunc()
> # include <internal/pycore_ceval.h> // _PyEval_EvalFrameDefault()
> #endif
> ---

IMO, this is a terrible suggestion that undermines the whole point of
having a private API.


> Contact me if you need help to update your affected projects.
>
> IMO PEP 523 doesn't have to be updated since it already says that the
> APIs are private.
>
> Since these APIs were added by PEP 523, I documented these changes in
> What's New in Python 3.11 > C API > Porting to Python 3.11,even if
> these APIs are private.
>
> Victor
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Hi,

On 22/03/2022 6:07 pm, Victor Stinner wrote:
> Hi,
>
> I proposed two PRs to move the private C API (Include/cpython/) of PEP
> 523 "Adding a frame evaluation API to CPython" to the internal C API
> (Include/internals/):
>
> * https://github.com/python/cpython/pull/32052
> * https://github.com/python/cpython/pull/32054

I just want to say that it is important the API is easy to use and access.

Otherwise there is a temptation to directly set the underlying function pointer, and that means we don't get to see when PEP 523 is used.
We might then mis-optimize on the assumption that PEP 523 isn't used.

Cheers,
Mark.

>
> API:
>
> * _PyFrameEvalFunction type
> * _PyInterpreterState_GetEvalFrameFunc()
> * _PyInterpreterState_SetEvalFrameFunc()
> * (undocumented) _PyEval_EvalFrameDefault()
>
> The private API to get/set the eval function *is* documented at:
> https://docs.python.org/dev/c-api/init.html#c._PyInterpreterState_GetEvalFrameFunc
>
> I added the Get/Set functions so debuggers don't have to access
> directly to the PyInterpreterState structure which has been moved to
> the internal C API in Python 3.8.
>
> This API causes me multiple issues:
>
> * It's a private API and I'm trying to remove the private API from the
> public C API header files.
> * The _PyFrameEvalFunction type is not stable: it got a new "tstate"
> parameter in Python 3.9 and the type of the second parameter changed
> from PyFrameObject* to _PyInterpreterFrame* in Python 3.11.
> * These functions use the _PyInterpreterFrame type which is part of
> the internal C API.
>
> While Pyston didn't bring a JIT compiler to Python with PEP 523,
> debuggers were made faster by using this API. Debuggers like pydevd,
> debugpy and ptvsd use it.
>
> I propose to move theses API to the internal header files
> (Include/internals/) to clarify that it's not part of the public C API
> and that there is no backward compatibility warranty.
>
> The change is being discussed at:
> https://bugs.python.org/issue46850
>
> --
>
> 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.
>
> Victor
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On Fri, 1 Apr 2022, 6:47 pm Victor Stinner, <vstinner@python.org> wrote:

> On Wed, Mar 30, 2022 at 5:42 PM Guido van Rossum <guido@python.org> wrote:
>
> I'm not convinced that advertising an API as being Unstable (in the
> documentation?) is going to solve any kind of problem. People love to
> use private APIs, and they do it simply because it's technically
> possible :-) At the end of the day, we have to help them updating
> their code, otherwise we (at least my Red Hat team) cannot update
> Python.
>
> I designed the internal C API to be more annoying to be used (need to
> define a macro, need more specific #include) in the hope that people
> will think twice before using it :-)
>


The changes you've made have been excellent, and the existing 3 categories
(stable public ABI, stable public API, unstable internal API) cover the
vast majority of cases.

The final case that isn't quite covered yet is to offer a "semi-stable" API
category for use cases that are intrinsically coupled to implementation
details that may change between feature releases, but should remain stable
within a release series.

The concrete motivating example for the new category is the extra APIs you
need in order to provide an alternative eval loop implementation.

The internal API category doesn't properly cover that case, as the APIs
there are free to change even in maintenance releases, and setting
Py_BUILD_CORE exposes a lot more than what an alternative eval loop would
need.

Regular public functions may work in some cases, but aren't necessarily
practical in others (such as exposing the internal frame details for use in
alternative eval loops).

From an implementation PoV, my own suggestion would be to define a new API
tier with an opt-in macro rather than relying solely on documentation or
naming conventions.

For example, define "Py_SEMI_STABLE_API" to opt in, with the headers under
"Include/cpython/semi_stable/" (I don't like "unstable" as potential
terminology here, since the internal API is already unstable - we're
splitting the difference between that and the long term stability of the
full public API)

Cheers,
Nick.



> Victor
> _______________________________________________
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> Code of Conduct: http://python.org/psf/codeofconduct/
>

+1 to Nick's analysis and proposal. I had been mulling over my own reply
but this just about covers it.

On Sun, Apr 3, 2022 at 6:29 AM Nick Coghlan <ncoghlan@gmail.com> wrote:

> On Fri, 1 Apr 2022, 6:47 pm Victor Stinner, <vstinner@python.org> wrote:
>
>> On Wed, Mar 30, 2022 at 5:42 PM Guido van Rossum <guido@python.org>
>> wrote:
>>
>> I'm not convinced that advertising an API as being Unstable (in the
>> documentation?) is going to solve any kind of problem. People love to
>> use private APIs, and they do it simply because it's technically
>> possible :-) At the end of the day, we have to help them updating
>> their code, otherwise we (at least my Red Hat team) cannot update
>> Python.
>>
>> I designed the internal C API to be more annoying to be used (need to
>> define a macro, need more specific #include) in the hope that people
>> will think twice before using it :-)
>>
>
>
> The changes you've made have been excellent, and the existing 3 categories
> (stable public ABI, stable public API, unstable internal API) cover the
> vast majority of cases.
>
> The final case that isn't quite covered yet is to offer a "semi-stable"
> API category for use cases that are intrinsically coupled to implementation
> details that may change between feature releases, but should remain stable
> within a release series.
>
> The concrete motivating example for the new category is the extra APIs you
> need in order to provide an alternative eval loop implementation.
>
> The internal API category doesn't properly cover that case, as the APIs
> there are free to change even in maintenance releases, and setting
> Py_BUILD_CORE exposes a lot more than what an alternative eval loop would
> need.
>
> Regular public functions may work in some cases, but aren't necessarily
> practical in others (such as exposing the internal frame details for use in
> alternative eval loops).
>
> From an implementation PoV, my own suggestion would be to define a new API
> tier with an opt-in macro rather than relying solely on documentation or
> naming conventions.
>
> For example, define "Py_SEMI_STABLE_API" to opt in, with the headers under
> "Include/cpython/semi_stable/" (I don't like "unstable" as potential
> terminology here, since the internal API is already unstable - we're
> splitting the difference between that and the long term stability of the
> full public API)
>
> Cheers,
> Nick.
>
>
>
>> Victor
>> _______________________________________________
>> 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
>> https://mail.python.org/archives/list/python-dev@python.org/message/YCHLFQ5KW6XF5C5CFWF4MRTZEXVBZBMA/
>> Code of Conduct: http://python.org/psf/codeofconduct/
>>
>

--
--Guido van Rossum (python.org/~guido)
*Pronouns: he/him **(why is my pronoun here?)*
<http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>

On Sun, Apr 3, 2022 at 6:32 AM Nick Coghlan <ncoghlan@gmail.com> wrote:

> On Fri, 1 Apr 2022, 6:47 pm Victor Stinner, <vstinner@python.org> wrote:
>
>> On Wed, Mar 30, 2022 at 5:42 PM Guido van Rossum <guido@python.org>
>> wrote:
>>
>> I'm not convinced that advertising an API as being Unstable (in the
>> documentation?) is going to solve any kind of problem. People love to
>> use private APIs, and they do it simply because it's technically
>> possible :-) At the end of the day, we have to help them updating
>> their code, otherwise we (at least my Red Hat team) cannot update
>> Python.
>>
>> I designed the internal C API to be more annoying to be used (need to
>> define a macro, need more specific #include) in the hope that people
>> will think twice before using it :-)
>>
>
>
> The changes you've made have been excellent, and the existing 3 categories
> (stable public ABI, stable public API, unstable internal API) cover the
> vast majority of cases.
>
> The final case that isn't quite covered yet is to offer a "semi-stable"
> API category for use cases that are intrinsically coupled to implementation
> details that may change between feature releases, but should remain stable
> within a release series.
>
> The concrete motivating example for the new category is the extra APIs you
> need in order to provide an alternative eval loop implementation.
>
> The internal API category doesn't properly cover that case, as the APIs
> there are free to change even in maintenance releases, and setting
> Py_BUILD_CORE exposes a lot more than what an alternative eval loop would
> need.
>
> Regular public functions may work in some cases, but aren't necessarily
> practical in others (such as exposing the internal frame details for use in
> alternative eval loops).
>
> From an implementation PoV, my own suggestion would be to define a new API
> tier with an opt-in macro rather than relying solely on documentation or
> naming conventions.
>
> For example, define "Py_SEMI_STABLE_API" to opt in, with the headers under
> "Include/cpython/semi_stable/" (I don't like "unstable" as potential
> terminology here, since the internal API is already unstable - we're
> splitting the difference between that and the long term stability of the
> full public API)
>
> Cheers,
> Nick.
>

+1 for an official "semi stable API tier".
It's already the case that essentially anything in Python can change,
it's just a question of how quickly and with how much friction.
Public APIs need to go through a multi-version deprecation cycle
(https://peps.python.org/pep-0387/#making-incompatible-changes).
Private internal APIs can (theoretically) change without notice between
patch releases.
There's a missing tier for APIs that can change without notice between
feature releases,
but are guaranteed(*) to be backwards compatible within a feature release,
and the PEP 523 frame evaluation API is an excellent example for this need
(maybe any newly added API should always go through this stage for a few
releases?).

Even though the docs (
https://docs.python.org/3.10/c-api/intro.html#include-files) explicitly
call out that _Py-prefixed APIs are internal and should not be used by
extensions,
this isn't the case in practice, so introducing the 3-tier concept could be
an opportunity
to clean up this situation a bit.
What exactly should be the naming conventions per tier, and the names of
the tiers,
is bikeshedding that should happen after there's agreement about the tiers
concept :-)

(*) "guaranteed" with exceptions of course (e.g. security or other critical
issue)


>
>
>
>> Victor
>> _______________________________________________
>> Python-Dev mailing list -- python-dev@python.org
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>> Code of Conduct: http://python.org/psf/codeofconduct/
>>
> _______________________________________________
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> Code of Conduct: http://python.org/psf/codeofconduct/
>

On Fri, Apr 1, 2022 at 2:06 AM Victor Stinner <vstinner@python.org> wrote:

> Hi,
>
> Update on this issue: I merged my 2 PRs.
> https://bugs.python.org/issue46850
>
> The following APIs have been moved to the internal C API:
>
> - _PyFrameEvalFunction type
> - _PyInterpreterState_GetEvalFrameFunc()
> - _PyInterpreterState_SetEvalFrameFunc()
> - _PyEval_EvalFrameDefault()
>
> If you use any of these API in your debugger/profiler project, you
> have do add something like the code below to your project:
> ---
> #ifndef Py_BUILD_CORE_MODULE
> # define Py_BUILD_CORE_MODULE
> #endif
> #include <Python.h>
> #if PY_VERSION_HEX >= 0x030B00A7
> # include <internal/pycore_interp.h> //
> _PyInterpreterState_SetEvalFrameFunc()
> # include <internal/pycore_ceval.h> // _PyEval_EvalFrameDefault()
> #endif
> ---
>
> Contact me if you need help to update your affected projects.
>
> IMO PEP 523 doesn't have to be updated since it already says that the
> APIs are private.
>

Thanks for bringing this up on python-dev, Victor. That was good. But the
point of the discussion should've been to continue working with people
based on the replies rather than proceeding to merge removals of the APIs
after people said they used them. (echoing Steve and Petr here...)

We discussed this on the steering council today. These APIs were in a weird
state and despite past decisions at the time of PEP-523
<https://peps.python.org/pep-0523/> in 2016 they should be treated as
public-ish rather than entirely private. Because we published a document
saying "here they are, use them!" and multiple projects have done so to
good effect.

For 3.11 we'd like those PRs reverted. We see the following as the better
way forward for these APIs:

Add a new #define that can be set before the #include <Python.h> that
exposes non-limited but stable within a bugfix/patch releases APIs (ie:
Petr's earlier suggestion).
These would be the first to fall within. To do so we should give these,
behind that #define, non _-prefixed "public style" names as these are
quasi-public and cannot be changed as readily as other true internals. We
still, per the PEP, reserve the right to turn these into no-op potentially
warning setting APIs in a future release (likely 3.12?) as they are at
least documented as being unstable/private in the PEP.

So in 3.11 these should continue to exist as in 3.6-3.10:
- _PyFrameEvalFunction type
- _PyInterpreterState_GetEvalFrameFunc()
- _PyInterpreterState_SetEvalFrameFunc()
- _PyEval_EvalFrameDefault()

AND in 3.11:
- #define protected versions of those without the leading _ become
available.
- (i'm intentionally not suggesting a #define name, y'all can pick
something)

In 3.12:
- the _ prefixed versions can go away. People using the APIs should've
updated their code to use the new #define and new names when building
against >=3.11 by then.
- Whether the APIs continue to be as useful and act as originally claimed
in PEP 523 is up to the 3.12 implementors (out of scope for this thread).
They occupy a newly defined middle ground between the "forever" style
limited API and the "can break even on bugfix/patch release" internal API
that wasn't a concept for us in 2016 when PEP 523 was written.

Why? Being conservative with things in active use that weren't *really*
private, and similar to what Mark Shannon and Petr said, we *do not* want
people to #define Py_BUILD_CORE_MODULE and start poking at internals in
arbitrary ways. That exposes a whole pile of other things for (ab)use that
are even more unstable. Avoiding that helps avoid temptation to go wild and
helps us identify users.

-gps (steering council hat on)


> Since these APIs were added by PEP 523, I documented these changes in
> What's New in Python 3.11 > C API > Porting to Python 3.11,even if
> these APIs are private.
>
> Victor
> --
> Night gathers, and now my watch begins. It shall not end until my death.
> _______________________________________________
> 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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> Code of Conduct: http://python.org/psf/codeofconduct/
>

On Sun, Apr 3, 2022 at 3:29 PM Nick Coghlan <ncoghlan@gmail.com> wrote:
> The changes you've made have been excellent, and the existing 3 categories (stable public ABI, stable public API, unstable internal API) cover the vast majority of cases.
>
> The final case that isn't quite covered yet is to offer a "semi-stable" API category for use cases that are intrinsically coupled to implementation details that may change between feature releases, but should remain stable within a release series.
>
> The concrete motivating example for the new category is the extra APIs you need in order to provide an alternative eval loop implementation.
>
> The internal API category doesn't properly cover that case, as the APIs there are free to change even in maintenance releases, and setting Py_BUILD_CORE exposes a lot more than what an alternative eval loop would need.
>
> Regular public functions may work in some cases, but aren't necessarily practical in others (such as exposing the internal frame details for use in alternative eval loops).
>
> From an implementation PoV, my own suggestion would be to define a new API tier with an opt-in macro rather than relying solely on documentation or naming conventions.
>
> For example, define "Py_SEMI_STABLE_API" to opt in, with the headers under "Include/cpython/semi_stable/" (I don't like "unstable" as potential terminology here, since the internal API is already unstable - we're splitting the difference between that and the long term stability of the full public API)

For me an API is either stable (remains the same forever) or unstable
(change time to time).

Public API means: stable, documented, tested.

Internal API means: unstable, not documented, not tested.

I'm not convinced that it's worth it to create something in the
middle. If you want to add doc and tests, it should become a public
stable API.

For example, IMO PyCode_New() (C API) and types.CodeType constructor
(Python API) should be moved to the internal C API, likely with a
deprecation period. Cython should not use it but a new stable API.

Victor
--
Night gathers, and now my watch begins. It shall not end until my death.
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Hi,

Steve, Petr: sorry if you feel that I didn't take your feedback in
account, it's not case. Thanks for your valuable feedback. It seems
like there was some misunderstanding.


On Tue, Apr 5, 2022 at 2:49 AM Gregory P. Smith <greg@krypto.org> wrote:
> Thanks for bringing this up on python-dev, Victor. That was good. But the point of the discussion should've been to continue working with people based on the replies rather than proceeding to merge removals of the APIs after people said they used them. (echoing Steve and Petr here...)
>
> We discussed this on the steering council today. These APIs were in a weird state and despite past decisions at the time of PEP-523 in 2016 they should be treated as public-ish rather than entirely private. Because we published a document saying "here they are, use them!" and multiple projects have done so to good effect.
>
> For 3.11 we'd like those PRs reverted.

Ok, I created https://github.com/python/cpython/pull/32343 to revert
these two PRs. I will merge it as soon as the Python 3.11 release
manager (Pablo) unblocks the main branch (he is currently preparing
the alpha7 release).


On Fri, Apr 1, 2022 at 12:36 PM Steve Dower <steve.dower@python.org> wrote:
> I don't see any additional discussion on the bug, and the prevailing
> opinion from actual users of this API is that it probably shouldn't
> change,

From what I understood my change basically only impacts "pydevd"
users. Fabio who works on that project said that he was fine with
that change ("I'm ok with changes"):
https://mail.python.org/archives/list/python-dev@python.org/message/XPDT55ANVKHGG74D62HDBOFLC4EXWJ26/

debugpy, ptvsd, PyDev, PyCharm and VSCode Python use the same code
base: https://github.com/fabioz/PyDev.Debugger

Jason Ansel of TorchDynamo was worried that the API couldn't be used
anymore. I replied that the API remains available. It's just about
adding a few lines of code (that I provided).

For me, all impacted users were made aware and joined the discussion.
It's very rare to be able to reach *all* users impacted by an
incompatible C API change!

If I understood correctly, all questions were replied. For example,
yes, the API remains accessible (with additional code), but no, sadly
the API is not stable (can change at each 3.x.0 major release, but
should not change in 3.x.y bugfix release).


On Fri, Apr 1, 2022 at 12:36 PM Steve Dower <steve.dower@python.org> wrote:
> and certainly shouldn't become internal without additional
> guarantees about stability.

The discussed API is not stable, Brett repeated that. The internal API
is not stable on purpose. I missed the discussion proposing to design
a stable API for PEP 523.

PEP 523 users are that the API is unstable and seem to be used to
update their code at each major (3.x) Python releases. I'm not
surprised that a debugger which requires a fast low-level access to
Python internals require that.

Or are you talking about not breaking the API in 3.x.y bugfix
releases? Currently, it's an unwritten rule. IMO it's well respected
by all core devs who understand that it's important to not break any
API, including private and internal APIs, in minor bugfix releases. My
changes are unrelated to that.


On Fri, Apr 1, 2022 at 1:24 PM Petr Viktorin <encukou@gmail.com> wrote:
> Now, the people who'd like a non-breaking solution will now need rush to
> develop and merge one until the next release, or the API breaks for
> users and it'll be too late to do anything about it.

We are talking about two projects (pydevd and TorchDynamo) and there
are 6 months until Python 3.11 final release (PEP 664). We are still
at the alpha phase, no? I don't see why a change only affecting two
projects is a big deal, knowing that these two projects have been made
aware, and I offered a patch that they can apply right now. They don't
need to wait for next October to apply my patch.


Anyway, I will revert my changes (once the main branch is unblocked)
to apply the SC's decision.

Victor
--
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On 4/5/2022 11:52 PM, Victor Stinner wrote:
> On Fri, Apr 1, 2022 at 12:36 PM Steve Dower <steve.dower@python.org> wrote:
>> I don't see any additional discussion on the bug, and the prevailing
>> opinion from actual users of this API is that it probably shouldn't
>> change,
>
> From what I understood my change basically only impacts "pydevd"
> users. Fabio who works on that project said that he was fine with
> that change ("I'm ok with changes"):
> https://mail.python.org/archives/list/python-dev@python.org/message/XPDT55ANVKHGG74D62HDBOFLC4EXWJ26/

"I'm okay with" isn't really a sign of support, particularly in this
kind of relationship where *we* have all the power. Fabio doesn't have a
choice but to be okay with whatever we decide, and he obviously accepts
that.

I'm still going to strongly advocate for not going out of our way to
break users like Fabio. Just because we have a reputation for doing it
doesn't mean we should keep doing it.

> For me, all impacted users were made aware and joined the discussion.
> It's very rare to be able to reach *all* users impacted by an
> incompatible C API change!

There's no way we reached all the users :) But we did reach more than usual.

> On Fri, Apr 1, 2022 at 12:36 PM Steve Dower <steve.dower@python.org> wrote:
>> and certainly shouldn't become internal without additional
>> guarantees about stability.
>
> The discussed API is not stable, Brett repeated that. The internal API
> is not stable on purpose. I missed the discussion proposing to design
> a stable API for PEP 523.

I can't tell whether you missed the discussion or if you're deliberately
misrepresenting it as a persuasive technique.

The API may not be "stable" according to our typical rules around public
C APIs, but it has explicit rules about its own stability (well, had,
though once the revert goes in it will have them again).

Nobody suggested making it *more* stable than it already was. We just
want to treat its existing stability rules with respect and either
transition out of them slowly, or leave them as they are.

Cheers,
Steve
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On Wed, 6 Apr 2022, 7:05 am Victor Stinner, <vstinner@python.org> wrote:

> On Sun, Apr 3, 2022 at 3:29 PM Nick Coghlan <ncoghlan@gmail.com> wrote:
> > The changes you've made have been excellent, and the existing 3
> categories (stable public ABI, stable public API, unstable internal API)
> cover the vast majority of cases.
> >
> > The final case that isn't quite covered yet is to offer a "semi-stable"
> API category for use cases that are intrinsically coupled to implementation
> details that may change between feature releases, but should remain stable
> within a release series.
> >
> > The concrete motivating example for the new category is the extra APIs
> you need in order to provide an alternative eval loop implementation.
> >
> > The internal API category doesn't properly cover that case, as the APIs
> there are free to change even in maintenance releases, and setting
> Py_BUILD_CORE exposes a lot more than what an alternative eval loop would
> need.
> >
> > Regular public functions may work in some cases, but aren't necessarily
> practical in others (such as exposing the internal frame details for use in
> alternative eval loops).
> >
> > From an implementation PoV, my own suggestion would be to define a new
> API tier with an opt-in macro rather than relying solely on documentation
> or naming conventions.
> >
> > For example, define "Py_SEMI_STABLE_API" to opt in, with the headers
> under "Include/cpython/semi_stable/" (I don't like "unstable" as potential
> terminology here, since the internal API is already unstable - we're
> splitting the difference between that and the long term stability of the
> full public API)
>
> For me an API is either stable (remains the same forever) or unstable
> (change time to time).
>
> Public API means: stable, documented, tested.
>
> Internal API means: unstable, not documented, not tested.
>
> I'm not convinced that it's worth it to create something in the
> middle. If you want to add doc and tests, it should become a public
> stable API.
>

The middle semi-stable tier formalises a concept that we already have: no
guarantees across feature releases, but both API and ABI stable within a
release series.

It's useful for tightly coupled projects like Cython, as it means they can
get core level performance without the risk of API compatibility breaks in
maintenance releases.

Without defining this tier, effectively the *entire* internal API becomes
semi-stable, as any changes made will risk breaking the third party
projects that we've told to define Py_BUILD_CORE when compiling.

Cheers,
Nick.



>

So here's my proposal:

- This API stays with the regular public API (Include/cpython/), but to
use it you'll need to #define Py_USING_UNSTABLE_API (name up for
bikeshedding).

- Since we're nearing Beta and there's no rush to break things, in 3.11
you only get a warning if you try to use it without the opt-in #define.
In 3.12 it'll fail.

- The functions will be renamed to drop the leading underscore. The old
names will be available as aliases (using #define) and may be removed
whenever the API changes. (Ideally, the underscore should always mark
API that's fully private with no guarantees at all.)

- The API will be stable during a minor release. (As usual, for extreme
cases, exceptions are possible with SC approval.)

- Docs will be updated:
- https://devguide.python.org/c-api/
- Individual reference entries for the API and the new opt-in macro


This applies to:

- Functions added in PEP 523
- PyCode_New, PyCode_NewWithPosOnlyArgs
- Ideally anything documented as subject to change between minor
releases. (To be kind to users, if something is added later we should
again have one release of compiler warnings before requiring the opt-in.
Unless that API just changed and users would get errors anyway.)


(Technically, this proposal needs SC approval -- PEP 387 exception for
PyCode_New*. I'll play by the rules, of course.)



On 06. 04. 22 17:21, Nick Coghlan wrote:
>
>
> On Wed, 6 Apr 2022, 7:05 am Victor Stinner, <vstinner@python.org
> <mailto:vstinner@python.org>> wrote:
>
> On Sun, Apr 3, 2022 at 3:29 PM Nick Coghlan <ncoghlan@gmail.com
> <mailto:ncoghlan@gmail.com>> wrote:
> > The changes you've made have been excellent, and the existing 3
> categories (stable public ABI, stable public API, unstable internal
> API) cover the vast majority of cases.
> >
> > The final case that isn't quite covered yet is to offer a
> "semi-stable" API category for use cases that are intrinsically
> coupled to implementation details that may change between feature
> releases, but should remain stable within a release series.
> >
> > The concrete motivating example for the new category is the extra
> APIs you need in order to provide an alternative eval loop
> implementation.
> >
> > The internal API category doesn't properly cover that case, as
> the APIs there are free to change even in maintenance releases, and
> setting Py_BUILD_CORE exposes a lot more than what an alternative
> eval loop would need.
> >
> > Regular public functions may work in some cases, but aren't
> necessarily practical in others (such as exposing the internal frame
> details for use in alternative eval loops).
> >
> > From an implementation PoV, my own suggestion would be to define
> a new API tier with an opt-in macro rather than relying solely on
> documentation or naming conventions.
> >
> > For example, define "Py_SEMI_STABLE_API" to opt in, with the
> headers under "Include/cpython/semi_stable/" (I don't like
> "unstable" as potential terminology here, since the internal API is
> already unstable - we're splitting the difference between that and
> the long term stability of the full public API)
>
> For me an API is either stable (remains the same forever) or unstable
> (change time to time).
>
> Public API means: stable, documented, tested.
>
> Internal API means: unstable, not documented, not tested.
>
> I'm not convinced that it's worth it to create something in the
> middle. If you want to add doc and tests, it should become a public
> stable API.
>
>
> The middle semi-stable tier formalises a concept that we already have:
> no guarantees across feature releases, but both API and ABI stable
> within a release series.
>
> It's useful for tightly coupled projects like Cython, as it means they
> can get core level performance without the risk of API compatibility
> breaks in maintenance releases.
>
> Without defining this tier, effectively the *entire* internal API
> becomes semi-stable, as any changes made will risk breaking the third
> party projects that we've told to define Py_BUILD_CORE when compiling.
>
> Cheers,
> Nick.
>
>
>
>
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On Thu, Apr 7, 2022 at 12:02 PM Petr Viktorin <encukou@gmail.com> wrote:
> - This API stays with the regular public API (Include/cpython/), but to
> use it you'll need to #define Py_USING_UNSTABLE_API (name up for
> bikeshedding).

Since there is already something similar called "Py_LIMITED", I
suggest dropping "USING_" for just: "Py_UNSTABLE_API".


> - The functions will be renamed to drop the leading underscore. The old
> names will be available as aliases (using #define) and may be removed
> whenever the API changes. (Ideally, the underscore should always mark
> API that's fully private with no guarantees at all.)

Should functions entering the "unstable API" be documented and tested?

For example, _PyEval_EvalFrameDefault() and
_PyInterpreterState_SetEvalFrameFunc() have no test nor doc.


> This applies to:
>
> - PyCode_New, PyCode_NewWithPosOnlyArgs

It would be nice to update Cython to define the Py_UNSTABLE_API macro
before the macro is required to get the function, since Cython still
uses PyCode_New().

Should we deprecate types.CodeType constructor in the Python API,
since types.CodeType.replace() exists and seems to be a better API
("more stable")?

Victor
--
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On 07. 04. 22 17:10, Victor Stinner wrote:
> On Thu, Apr 7, 2022 at 12:02 PM Petr Viktorin <encukou@gmail.com> wrote:
>> - This API stays with the regular public API (Include/cpython/), but to
>> use it you'll need to #define Py_USING_UNSTABLE_API (name up for
>> bikeshedding).
>
> Since there is already something similar called "Py_LIMITED", I
> suggest dropping "USING_" for just: "Py_UNSTABLE_API".

But I really like the explicit “USING” :)
I don't think there's too much value in these two being consistent.
(Yay, bikeshedding!)


>> - The functions will be renamed to drop the leading underscore. The old
>> names will be available as aliases (using #define) and may be removed
>> whenever the API changes. (Ideally, the underscore should always mark
>> API that's fully private with no guarantees at all.)
>
> Should functions entering the "unstable API" be documented and tested?
>
> For example, _PyEval_EvalFrameDefault() and
> _PyInterpreterState_SetEvalFrameFunc() have no test nor doc.

Yes.
I'll add docs, for tests I'll at least open an issue.


>> This applies to:
>>
>> - PyCode_New, PyCode_NewWithPosOnlyArgs
>
> It would be nice to update Cython to define the Py_UNSTABLE_API macro
> before the macro is required to get the function, since Cython still
> uses PyCode_New().

That (for any project, not just Cython) is why I propose warnings in
3.11, before requiring the opt-in in 3.12.


> Should we deprecate types.CodeType constructor in the Python API,
> since types.CodeType.replace() exists and seems to be a better API
> ("more stable")?

I don't know. But it's for a different discussion.
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On Thu, 7 Apr 2022, 8:02 pm Petr Viktorin, <encukou@gmail.com> wrote:

> So here's my proposal:
>
> - This API stays with the regular public API (Include/cpython/), but to
> use it you'll need to #define Py_USING_UNSTABLE_API (name up for
> bikeshedding).
>

I'm fine with the rest of what you suggest, but I don't think this is the
right mechanical approach:

* "unstable" is the wrong term. We already have an unstable API tier: the
internal API, which can change even in maintenance releases. The value of
the new tier is that it is "semi stable": stable in maintenance releases,
unstable in feature releases.
* the lesson I take from our stable ABI experience is that mixing two tiers
of the API in a single header file is hard to maintain, as it's too easy to
add a new API to the wrong section. A separate file that gets included
automatically from the relevant header file(s) when the new definition is
used makes the split much clearer.

Cheers,
Nick.



>
>

On Thu, 7 Apr 2022, 8:02 pm Petr Viktorin, <encukou@gmail.com> wrote:

>
> This applies to:
>
> - Functions added in PEP 523
> - PyCode_New, PyCode_NewWithPosOnlyArgs
> - Ideally anything documented as subject to change between minor
> releases. (To be kind to users, if something is added later we should
> again have one release of compiler warnings before requiring the opt-in.
> Unless that API just changed and users would get errors anyway.)
>


Other candidate items for this tier:


* non-opaque access to frame structs and any other key APIs needed to
implement alternate eval loops with comparable performance to the default
eval loop (unless & until we can figure out stable public APIs that can
deliver equivalent performance)

> * C APIs that provide access to compiled code whether in AST or opcode
form (the API itself may be stable, but the compiled code isn't, so this is
kinda covered by your last point)

Cheers,
Nick.


>

Here's the issue with the plan (including Nick's suggestions):
https://github.com/python/cpython/issues/91744

On Sun, Apr 10, 2022 at 5:43 AM Nick Coghlan <ncoghlan@gmail.com> wrote:
>
> On Thu, 7 Apr 2022, 8:02 pm Petr Viktorin, <encukou@gmail.com> wrote:
>>
>> So here's my proposal:
>>
>> - This API stays with the regular public API (Include/cpython/), but to
>> use it you'll need to #define Py_USING_UNSTABLE_API (name up for
>> bikeshedding).
>
>
> I'm fine with the rest of what you suggest, but I don't think this is the right mechanical approach:
>
> * "unstable" is the wrong term. We already have an unstable API tier: the internal API, which can change even in maintenance releases. The value of the new tier is that it is "semi stable": stable in maintenance releases, unstable in feature releases.
> * the lesson I take from our stable ABI experience is that mixing two tiers of the API in a single header file is hard to maintain, as it's too easy to add a new API to the wrong section. A separate file that gets included automatically from the relevant header file(s) when the new definition is used makes the split much clearer.
>
> Cheers,
> Nick.
>
>
>>
>>
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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?


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> escreveu:
>>>
>>> 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_frame_evaluator.template.pyx#L187
>> https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd_frame_evaluator.template.pyx#L232
>> https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd_frame_evaluator.template.pyx#L311
>>
>> 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_frame_evaluator.template.pyx#L491) 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 there's some effort not to break things unless really needed -- ideally with instructions on how to port).
>>
>> 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 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
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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>
> escreveu:
> >>>
> >>> 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_frame_evaluator.template.pyx#L187
> >>
> https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd_frame_evaluator.template.pyx#L232
> >>
> https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd_frame_evaluator.template.pyx#L311
> >>
> >> 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_frame_evaluator.template.pyx#L491)
> 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
> there's some effort not to break things unless really needed -- ideally
> with instructions on how to port).
> >>
> >> 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
> 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
> https://mail.python.org/archives/list/python-dev@python.org/message/DHKE7LVN4R7NQFTBJJHGXI3AJOK6OYIV/
> > Code of Conduct: http://python.org/psf/codeofconduct/
>

On 22. 04. 22 14:47, Fabio Zadrozny wrote:
>
>
> Em sex., 22 de abr. de 2022 às 09:02, Petr Viktorin <encukou@gmail.com
> <mailto: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?

PyFrameObject is a fairly thin wrapper around _PyInterpreterFrame -- it
adds PyObject metadata (type & refcount), and not much else. It's
allocated at most once for each _PyInterpreterFrame -- once it's created
it stays attached to the frame.
So, for the most heavily optimized code paths a PyFrameObject is not
allocated, but it's trivial to get it whenever it's needed.

> -- 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).

Ah, you also need PyEval_EvalFrameDefault exposed. The public version
would take PyFrameObject and pass its _PyInterpreterFrame to the
internal _PyEval_EvalFrameDefault.


> On Thu, Mar 24, 2022 at 8:13 PM Fabio Zadrozny <fabiofz@gmail.com
> <mailto:fabiofz@gmail.com>> wrote:
> >
> >
> > Em qui., 24 de mar. de 2022 às 15:39, Fabio Zadrozny
> <fabiofz@gmail.com <mailto:fabiofz@gmail.com>> escreveu:
> >>>
> >>> 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_frame_evaluator.template.pyx#L187
> <https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd_frame_evaluator.template.pyx#L187>
> >>
> https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd_frame_evaluator.template.pyx#L232
> <https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd_frame_evaluator.template.pyx#L232>
> >>
> https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd_frame_evaluator.template.pyx#L311
> <https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd_frame_evaluator.template.pyx#L311>
> >>
> >> 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_frame_evaluator.template.pyx#L491
> <https://github.com/fabioz/PyDev.Debugger/blob/main/_pydevd_frame_eval/pydevd_frame_evaluator.template.pyx#L491>)
> 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 there's some effort not to break things unless really needed
> -- ideally with instructions on how to port).
> >>
> >> 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 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
> <mailto:python-dev@python.org>
> > To unsubscribe send an email to python-dev-leave@python.org
> <mailto:python-dev-leave@python.org>
> > https://mail.python.org/mailman3/lists/python-dev.python.org/
> <https://mail.python.org/mailman3/lists/python-dev.python.org/>
> > Message archived at
> https://mail.python.org/archives/list/python-dev@python.org/message/DHKE7LVN4R7NQFTBJJHGXI3AJOK6OYIV/
> <https://mail.python.org/archives/list/python-dev@python.org/message/DHKE7LVN4R7NQFTBJJHGXI3AJOK6OYIV/>
> > Code of Conduct: http://python.org/psf/codeofconduct/
> <http://python.org/psf/codeofconduct/>
>
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On Fri, Apr 22, 2022 at 2:52 PM Fabio Zadrozny <fabiofz@gmail.com> wrote:
> 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.

You can already modify _PyInterpreterFrame.f_code using the internal C API.

> 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?

There is no public C API to modify the "f_code" attribute of a
PyFrameObject. There is only PyFrame_GetCode() *getter*.

Victor
--
Night gathers, and now my watch begins. It shall not end until my death.
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