On 06. 12. 21 21:50, Guido van Rossum wrote:
On Mon, Dec 6, 2021 at 12:12 PM Petr Viktorin <encu...@gmail.com
<mailto:encu...@gmail.com>> wrote:
On 06. 12. 21 20:29, Guido van Rossum wrote:
> Hi Petr,
>
> In PEP 384 it is written that no functions starting with an
underscore
> are part of the stable ABI:
>
> PEP 384 -- Defining a Stable ABI | Python.org
> <https://www.python.org/dev/peps/pep-0384/#excluded-functions
<https://www.python.org/dev/peps/pep-0384/#excluded-functions>>
> > All functions starting with _Py are not available to applications
>
> OTOH there's a data file in the repo, Misc/stabe_abi.txt, which
lists
> many functions starting with _Py_, for example
_PyObject_GC_Malloc. Then
> again, that function is not listed in Doc/data/stable_abi.dat. (I
didn't
> check other functions, but maybe there are others.)
>
> So is Misc/stable_abi.txt just out of date? Or how can the
discrepancy
> be explained?
These are not part of the limited API, so extension authors can't use
them in the C source. But they typically are (or have been) called by
macros from the limited API. So, they are part of the stable ABI; they
need to be exported.
Misc/stable_abi.txt says "abi_only" for all of these. They don't
show up
in the user-facing docs.
Thanks, that helps. It's too bad that there's no comment at the top
explaining the format (in fact it appears to discourage reading the file?).
You can read it, but I want to discourage people from relying on the
format: Tools/scripts/stable_abi.py should be the only consumer.
I will add a comment though.
Also, it looks like Mark is proposing to *remove* _PyObject_GC_Malloc
from stable_abi.txt in https://github.com/python/cpython/pull/29879
<https://github.com/python/cpython/pull/29879> Is that allowed? If it's
being used by a macro it means code using that macro will fail unless
recompiled for 3.11.
Generally, that's not allowed. In this particular case, Victor's
analysis is right: if you trawl through the history from 3.2 on, you can
see that you can't call _PyObject_GC_Malloc via macros in the limited
API. So yes, this one can be removed.
I'll also note that removing things that are "allowed" to go is not nice
to people who relied on PEP 384, which says that defining Py_LIMITED_API
"will hide all definitions that are not part of the ABI" -- even though
that's incompatible with the part where it says "All functions starting
with _Py are not available to applications".
PEP 384 is a historical document, but before 3.10 it was the best
available documentation. PEP 652 sort of changed the rules mid-course
(ref. https://www.python.org/dev/peps/pep-0652/#backwards-compatibility).
But for _PyObject_GC_Malloc specifically, IMO the speedup is worth it.
Go ahead and remove it.
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