[pypy-dev] PyCodeObject incompatibility

[Carl Friedrich Bolz-Tereick]

Hi Dmitry,

I can only reiterate, we would need some information about what that
library is actually for to give more useful information at this point.
As Matti said, most of these APIs cannot be usefully implemented in
PyPy. most jitted functions do not *have* a filled frame object at all
in PyPy. so if you want to access the frames, you need to leave the
jit-produced machine code, which is very slow.

Cheers,

CF

On 15.02.22 04:15, Dmitry Kovner wrote:
> Hi, again! First of all, thanks for the fast reply! The answer helped me
> a lot. However, during the porting of the extension to the awesome PyPy,
> I've got more questions:
> 1. The extension uses opcodes from cPython's opcode.h header file.
> (https://github.com/python/cpython/blob/8a84aef0123bd8c13cf81fbc3b5f6d45f96c2656/Include/opcode.h
> <https://github.com/python/cpython/blob/8a84aef0123bd8c13cf81fbc3b5f6d45f96c2656/Include/opcode.h>)
> There is no such file in the implementation of C API in PyPy. What could
> you recommend as the best alternative?
> 2. The extension uses some fields of PyThreadState structure. For
> example, its frame field
> (https://github.com/python/cpython/blob/8a84aef0123bd8c13cf81fbc3b5f6d45f96c2656/Include/cpython/pystate.h#L59
> <https://github.com/python/cpython/blob/8a84aef0123bd8c13cf81fbc3b5f6d45f96c2656/Include/cpython/pystate.h#L59>).
> Is it right to use PyObject_GetAttrString() to access that field in PyPy
> C API?
> 3. There is no function PyFrame_FastToLocals
> (https://github.com/python/cpython/blob/8a84aef0123bd8c13cf81fbc3b5f6d45f96c2656/Objects/frameobject.c#L931
> <https://github.com/python/cpython/blob/8a84aef0123bd8c13cf81fbc3b5f6d45f96c2656/Objects/frameobject.c#L931>)
> in the C API of PyPy. Are there any alternatives?
> 4. Functions PyEval_SetTrace(), PyEval_SetProfile(),
> PyFrame_GetLineNumber() are defined only in stubs.py in PyPy.
> (https://foss.heptapod.net/pypy/pypy/-/blob/branch/py3.7/pypy/module/cpyext/stubs.py#L918
> <https://foss.heptapod.net/pypy/pypy/-/blob/branch/py3.7/pypy/module/cpyext/stubs.py#L918>)
> Is there a way to get that information in PyPy except patching of its
> source code?
> 5. Are there any analogues of all PyTrace_* constants
> (https://github.com/python/cpython/blob/8a84aef0123bd8c13cf81fbc3b5f6d45f96c2656/Include/cpython/pystate.h#L26
> <https://github.com/python/cpython/blob/8a84aef0123bd8c13cf81fbc3b5f6d45f96c2656/Include/cpython/pystate.h#L26>)
> in the PyPy C API?
> 6. There is no function PyFrame_Check()
> (https://github.com/python/cpython/blob/8a84aef0123bd8c13cf81fbc3b5f6d45f96c2656/Include/frameobject.h#L53
> <https://github.com/python/cpython/blob/8a84aef0123bd8c13cf81fbc3b5f6d45f96c2656/Include/frameobject.h#L53>)
> in the PyPy C API. Are there any alternatives?
>
> I'm really sorry for the long question! I hope the list of the problems
> described above is full enough to port the extension and I will have no
> more questions. :)
>
> Best regards, Dmitrii
>
> чт, 10 февр. 2022 г. в 23:07, Armin Rigo <armin.rigo at gmail.com
> <mailto:armin.rigo at gmail.com>>:
>
>     Hi,
>
>     On Thu, 10 Feb 2022 at 14:03, Dmitry Kovner <dmitryk at lightrun.com
>     <mailto:dmitryk at lightrun.com>> wrote:
>      > Hello! I'm trying to build a low-level C API extension of cPython
>     to be used in PyPy. The extension extensively uses some fields of
>     PyCodeObject
>     (https://github.com/python/cpython/blob/f87e616af038ee8963185e11b96841c81e8ef15a/Include/code.h#L23
>     <https://github.com/python/cpython/blob/f87e616af038ee8963185e11b96841c81e8ef15a/Include/code.h#L23>):
>     co_firstlineno, co_stacksize, co_consts and so on. However, it seems
>     these fields are not defined in the similar structure of the PyPy
>     implementation:
>     https://foss.heptapod.net/pypy/pypy/-/blob/branch/py3.8/pypy/module/cpyext/include/code.h#L7
>     <https://foss.heptapod.net/pypy/pypy/-/blob/branch/py3.8/pypy/module/cpyext/include/code.h#L7>.
>     Is it possible to get values of these fields using PyPy C API somehow?
>
>     Yes, it's a limitation of PyPy not to expose these fields.  If you
>     want to write portable code that always works, the simplest is to call
>     `PyObject_GetAttrString(code, "__consts__")` etc.  Remember that you
>     need to call `Py_DECREF()` on the result at some point.
>
>
>     A bientôt,
>
>     Armin.
>
>
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