pyfpe.h: Exclude PyFPE_START_PROTECT and PyFPE_END_PROTECT from the Py_LIMITED_API

[vstinner]

BPO	38835
Nosy	@vstinner
PRs	bpo-38835: Exclude PyFPE macros from the stable API #17228 bpo-38835: Don't use PyFPE_START_PROTECT and PyFPE_END_PROTECT #17231

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2019-11-20.11:19:41.795>
created_at = <Date 2019-11-18.14:35:51.139>
labels = ['library', '3.9']
title = 'pyfpe.h: Exclude PyFPE_START_PROTECT and PyFPE_END_PROTECT from the Py_LIMITED_API'
updated_at = <Date 2019-11-20.11:19:41.792>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2019-11-20.11:19:41.792>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2019-11-20.11:19:41.795>
closer = 'vstinner'
components = ['Library (Lib)']
creation = <Date 2019-11-18.14:35:51.139>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 38835
keywords = ['patch']
message_count = 5.0
messages = ['356870', '356871', '357021', '357059', '357060']
nosy_count = 1.0
nosy_names = ['vstinner']
pr_nums = ['17228', '17231']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue38835'
versions = ['Python 3.9']

[vstinner]

The bpo-29137 removed the fpectl module. But two macros were kept in pyfpe.h:

/* These macros used to do something when Python was built with --with-fpectl,

• but support for that was dropped in 3.7. We continue to define them though,
• to avoid breaking API users.
  */

#define PyFPE_START_PROTECT(err_string, leave_stmt)
#define PyFPE_END_PROTECT(v)

I propose to exclude them from the stable API. Maybe at least exclude them from the stable API >= 3.9?

commit 735ae8d
Author: Nathaniel J. Smith <njs@pobox.com>
Date: Fri Jan 5 23:15:34 2018 -0800

bpo-29137: Remove fpectl module (bpo-4789)

This module has never been enabled by default, never worked correctly
on x86-64, and caused ABI problems that caused C extension
compatibility. See bpo-29137 for details/discussion.

[vstinner]

Python/pyfpe.c still contains two variables (PyFPE_jbuf and PyFPE_counter) and one function (PyFPE_dummy) for ABI compatibility:
---
/* These variables used to be used when Python was built with --with-fpectl,

• but support for that was dropped in 3.7. We continue to define them,
• though, because they may be referenced by extensions using the stable ABI.
  */

#include "setjmp.h"

jmp_buf PyFPE_jbuf;
int PyFPE_counter;

double
PyFPE_dummy(void *dummy)
{
    return 1.0;
}

---

[vstinner]

New changeset be143ec by Victor Stinner in branch 'master':
bpo-38835: Don't use PyFPE_START_PROTECT and PyFPE_END_PROTECT (GH-17231)
be143ec

[vstinner]

New changeset 488d02a by Victor Stinner in branch 'master':
bpo-38835: Exclude PyFPE macros from the stable API (GH-17228)
488d02a

[vstinner]

Pablo asked on PR 17231:

Do you want to left the empty macro in Include/pyfpe.h?

#17231 (review)

I replied:

If someone wants to remove them, I would suggest to first deprecate them, and wait at least one Python release before removing them. And do that in a separated issue: https://bugs.python.org/issue38835 title is "pyfpe.h: Exclude PyFPE_START_PROTECT and PyFPE_END_PROTECT from the Py_LIMITED_API", it's not directly related :-)

#17231 (comment)

In short, I'm not interested to remove it right now :-)

The initial issue has been fixed, so I close the issue. Thanks for your review Pablo ;-)