Depreciated MACRO of copysign for MSVC

[ejguan]

BPO	42120
Nosy	@pfmoore, @ronaldoussoren, @tjguk, @zware, @zooba, @miss-islington, @ejguan
PRs	bpo-42120: Remove macro defining copysign to _copysign on Windows #23326 [3.8] bpo-42120: Remove macro defining copysign to _copysign on Windows (GH-23326) #23330 [3.9] bpo-42120: Remove macro defining copysign to _copysign on Windows (GH-23326) #23331

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

Show more details

GitHub fields:

assignee = 'https://github.com/zooba'
closed_at = <Date 2020-11-21.01:10:32.360>
created_at = <Date 2020-10-22.19:08:50.650>
labels = ['3.8', '3.9', '3.10', 'expert-C-API', 'build', 'OS-windows']
title = 'Depreciated MACRO of copysign for MSVC'
updated_at = <Date 2020-11-21.01:10:32.360>
user = 'https://github.com/ejguan'

bugs.python.org fields:

activity = <Date 2020-11-21.01:10:32.360>
actor = 'steve.dower'
assignee = 'steve.dower'
closed = True
closed_date = <Date 2020-11-21.01:10:32.360>
closer = 'steve.dower'
components = ['Windows', 'C API']
creation = <Date 2020-10-22.19:08:50.650>
creator = 'ejguan'
dependencies = []
files = []
hgrepos = []
issue_num = 42120
keywords = ['patch']
message_count = 7.0
messages = ['379323', '379325', '379570', '381174', '381181', '381186', '381217']
nosy_count = 7.0
nosy_names = ['paul.moore', 'ronaldoussoren', 'tim.golden', 'zach.ware', 'steve.dower', 'miss-islington', 'ejguan']
pr_nums = ['23326', '23330', '23331']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue42120'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

[ejguan]

At

cpython/PC/pyconfig.h

Line 196 in c60394c

#define copysign _copysign

, the MACRO converts copysign to _copysign. This MACRO is defined 13 years ago and it's really dangerous to define a lower-letter MACRO at this low level.
Currently, MSVC is supporting copysign (https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/copysign-copysignf-copysignl-copysign-copysignf-copysignl?view=vs-2019).
I am requesting to remove this MACRO, as my customized copysign API will also be converted to _copysign on MSVC platform.

[zooba]

Sounds good, but I don't think we can backport it. It's not _our_ public API, but it's still going to impact compiling modules.

Also, looking at the docs link above, copysign() is for floats and _copysign() is for doubles, which means it's an actual functional change. If POSIX/libc copysign() is floats, it's probably fine for a 3.10 change, but if we need to preserve the type then it needs to become _Py_copysign throughout.

[ronaldoussoren]

The standard is for copysign to work on doubles, with copysignf as the same functionality for floats.

https://en.cppreference.com/w/c/numeric/math/copysign

[zooba]

Turns out a straight delete is fine, as both names are defined in UCRT. I think it's safe to backport as well, since it's only going to affect other people's code poorly (and they'll need to recompile to see any change anyway).

[zooba]

New changeset 9cc9e27 by Steve Dower in branch 'master':
bpo-42120: Remove macro defining copysign to _copysign on Windows (GH-23326)
9cc9e27

[miss-islington]

New changeset 4f54ca0 by Miss Islington (bot) in branch '3.8':
bpo-42120: Remove macro defining copysign to _copysign on Windows (GH-23326)
4f54ca0

[miss-islington]

New changeset 2c38e49 by Miss Islington (bot) in branch '3.9':
[3.9] bpo-42120: Remove macro defining copysign to _copysign on Windows (GH-23326) (GH-23331)
2c38e49