Issue 29943: PySlice_GetIndicesEx change broke ABI in 3.5 and 3.6 branches

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classification

Title:	PySlice_GetIndicesEx change broke ABI in 3.5 and 3.6 branches
Type:	behavior	Stage:	resolved
Components:	Interpreter Core	Versions:	Python 3.6, Python 3.5, Python 2.7

process

Status:	closed	Resolution:	fixed
Dependencies:		Superseder:
Assigned To:	serhiy.storchaka	Nosy List:	arigo, benjamin.peterson, cgohlke, cstratak, hroncok, jhelmus, josh.r, larry, mark.dickinson, ned.deily, njs, serhiy.storchaka, skrah, steve.dower
Priority:	release blocker	Keywords:

Created on 2017-03-29 23:36 by njs, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Pull Requests
URL	Status	Linked	Edit
PR 1049	merged	serhiy.storchaka, 2017-04-08 09:26
PR 1050	merged	serhiy.storchaka, 2017-04-08 09:27
PR 1813	merged	serhiy.storchaka, 2017-05-25 11:27
PR 2015		dino.viehland, 2017-06-09 01:22

Messages (27)
msg290796 - (view)	Author: Nathaniel Smith (njs) *	Date: 2017-03-29 23:36
In the process of fixing issue 27867, a new function PySlice_AdjustIndices was added, and PySlice_GetIndicesEx was converted into a macro that calls this new function. The patch was backported to both the 3.5 and 3.6 branches, was released in 3.6.1, and is currently slated to be released as part of 3.5.4. Unfortunately, this breaks our normal ABI stability guarantees for micro releases: it means that if a C module that uses PySlice_GetIndicesEx is compiled against e.g. 3.6.1, then it cannot be imported on 3.6.0. This affects a number of high-profile packages (cffi, pandas, mpi4py, dnf, ...). The only workaround is that if you are distributing binary extension modules (e.g. wheels), then you need to be careful not to upgrade to 3.6.1. It's not possible for a wheel to declare that it requires 3.6.1-or-better, because CPython normally follows the rule that we don't make these kinds of changes. Oops. CC'ing Ned and Larry, because it's possible this should trigger a 3.6.2, and I think it's a blocker for 3.5.4. CC'ing Serhiy as the author of the original patch, since you probably have the best idea how this could be unwound with minimal breakage :-). python-dev discussion:

msg290796 - (view)

Author: Nathaniel Smith (njs) * (Python committer)

Date: 2017-03-29 23:36

In the process of fixing issue 27867, a new function PySlice_AdjustIndices was added, and PySlice_GetIndicesEx was converted into a macro that calls this new function. The patch was backported to both the 3.5 and 3.6 branches, was released in 3.6.1, and is currently slated to be released as part of 3.5.4.

Unfortunately, this breaks our normal ABI stability guarantees for micro releases: it means that if a C module that uses PySlice_GetIndicesEx is compiled against e.g. 3.6.1, then it cannot be imported on 3.6.0. This affects a number of high-profile packages (cffi, pandas, mpi4py, dnf, ...). The only workaround is that if you are distributing binary extension modules (e.g. wheels), then you need to be careful not to upgrade to 3.6.1. It's not possible for a wheel to declare that it requires 3.6.1-or-better, because CPython normally follows the rule that we don't make these kinds of changes. Oops.

CC'ing Ned and Larry, because it's possible this should trigger a 3.6.2, and I think it's a blocker for 3.5.4. CC'ing Serhiy as the author of the original patch, since you probably have the best idea how this could be unwound with minimal breakage :-).

python-dev discussion: