Drop libpython38.a from Windows release

[zooba]

BPO	37351
Nosy	@pfmoore, @tjguk, @ocroquette, @merwok, @zware, @zooba, @dstufft
PRs	bpo-37351: Removes libpython38.a from standard Windows distribution #14276 [3.8] bpo-37351: Removes libpython38.a from standard Windows distribution (GH-14276) #14298

^{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 = 'https://github.com/zooba'
closed_at = <Date 2019-06-24.17:32:22.237>
created_at = <Date 2019-06-20.16:54:16.730>
labels = ['3.8', 'type-bug', 'library', '3.9', 'OS-windows']
title = 'Drop libpython38.a from Windows release'
updated_at = <Date 2020-11-04.22:27:40.159>
user = 'https://github.com/zooba'

bugs.python.org fields:

activity = <Date 2020-11-04.22:27:40.159>
actor = 'ocroquette'
assignee = 'steve.dower'
closed = True
closed_date = <Date 2019-06-24.17:32:22.237>
closer = 'steve.dower'
components = ['Distutils', 'Windows']
creation = <Date 2019-06-20.16:54:16.730>
creator = 'steve.dower'
dependencies = []
files = []
hgrepos = []
issue_num = 37351
keywords = ['patch']
message_count = 7.0
messages = ['346136', '346138', '346151', '346254', '346300', '346421', '380373']
nosy_count = 7.0
nosy_names = ['paul.moore', 'tim.golden', 'ocroquette', 'eric.araujo', 'zach.ware', 'steve.dower', 'dstufft']
pr_nums = ['14276', '14298']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue37351'
versions = ['Python 3.8', 'Python 3.9']

[zooba]

The step of generating a MinGW import library for Python releases is very rarely used, forces us to take extra build dependencies, and is better handled by the end-users who need it.

We will drop the libpython38.a file from the main distribution, and update the docs to contain the commands necessary (users who are using MinGW will have these tools easily available):

gendef python38.dll > tmp.def
dlltool --dllname python38.dll --def tmp.def --output-lib libpython38.a

Here is where Anaconda have been doing this themselves, rather than relying on our distributed file: https://github.com/AnacondaRecipes/aggregate/blob/master/libpython-feedstock/recipe/bld.bat

We also heard that the regex module no longer relies on this: https://mail.python.org/archives/list/python-dev@python.org/message/A7IXOTARTYJUNSCFAU3YY2VOVILC4EBY/

A few people do regularly use this file, according to https://mobile.twitter.com/zooba/status/1139661637521031168 which is why including the instructions and porting notes is important. I haven't heard from any of them that they would have trouble running the above commands themselves.

[zooba]

Realising that this may have an impact on distutils.cygwincompiler.Mingw32CCompiler, but I can't tell from the source code how/whether it would pick up the pre-packaged libpython38.a. Does anyone know?

[zooba]

Turns out that using distutils/setuptools with --compiler=mingw32 is just doomed to fail when it hits get_msvcr(), which has never been updated for Python 3.5 onwards.

So I think it's probably safe to assume that this scenario isn't a real thing and people are linking MinGW/Python in some other way?

[zooba]

New changeset f569092 by Steve Dower in branch 'master':
bpo-37351: Removes libpython38.a from standard Windows distribution (bpo-14276)
f569092

[zooba]

New changeset fa23bd2 by Steve Dower in branch '3.8':
bpo-37351: Removes libpython38.a from standard Windows distribution (GH-14276)
fa23bd2

[zooba]

Fixing --compiler=mingw32 is left for another bug, if anyone is so motivated.

[ocroquette]

I don't know what version of gendef is meant, but the one from MSYS2 / MinGW64 doesn't output the result on stdout, but rather writes the file "python38.def" itself. So the commands are the following:

cd libs
gendef ..\python38.dll
dlltool --dllname python38.dll --def python38.def --output-lib libpython38.a