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classification
Title: Update PC/pyconfig.h to support disabling auto linking
Type: enhancement Stage: patch review
Components: Windows Versions: Python 3.9, Python 3.8, Python 3.7, Python 3.6
process
Status: open Resolution:
Dependencies: Superseder:
Assigned To: Nosy List: Jean-Christophe Fillion-Robin, mathstuf, paul.moore, python-dev, steve.dower, tim.golden, zach.ware
Priority: normal Keywords: patch

Created on 2019-11-06 22:41 by Jean-Christophe Fillion-Robin, last changed 2022-04-11 14:59 by admin.

Pull Requests
URL Status Linked Edit
PR 19740 open python-dev, 2020-04-27 19:19
Messages (6)
msg356158 - (view) Author: Jean-Christophe Fillion-Robin (Jean-Christophe Fillion-Robin) * Date: 2019-11-06 22:41
When configuring project using build-system generator like CMake, the linking is explicitly handled and does not to be implicitly hard-coded in pyconfig.h

Having the "pythonXY.lib" library hard-coded in pyconfig.h currently requires to explicitly specify a link directory. While possible, this require to increase the complexity of our build-system.

I suggest we introduce a new macro (e.g PY_CONFIG_AUTOLINK_DISABLED)
msg356310 - (view) Author: Steve Dower (steve.dower) * (Python committer) Date: 2019-11-09 22:53
I'm not totally averse to just removing the link pragmas completely, but since that's got significant compatibility impact, I'm happy with this approach.

Let's shorten the name though. "PY_NO_LINK_LIB" might be better?
msg356365 - (view) Author: Jean-Christophe Fillion-Robin (Jean-Christophe Fillion-Robin) * Date: 2019-11-11 15:46
PY_NO_LINK_LIB will work well. I will work on a patch later this week.
msg368474 - (view) Author: Jean-Christophe Fillion-Robin (Jean-Christophe Fillion-Robin) * Date: 2020-05-08 21:58
Associated pull request has been updated, CLA signed and it is ready for final review and integration.

Thanks so much for your time,
msg368744 - (view) Author: Steve Dower (steve.dower) * (Python committer) Date: 2020-05-12 22:20
Thanks for the ping - sorry, I've been largely offline while I'm between internet providers.

The change is fine, but I wonder whether we should document it somewhere? Most likely in the devguide, which is in a separate repo, but perhaps a mention in PCbuild/readme.txt too?

Presumably you looked around for ideas before figuring out the issue - anywhere you might have found it? Just in the source code?
msg368749 - (view) Author: Ben Boeckel (mathstuf) Date: 2020-05-12 23:29
> Presumably you looked around for ideas before figuring out the issue

Usually when "could not find foo.lib" popping up without any mention of "foo.lib" on the link line points directly to these "autolinking" "features" being the culprit. It's just something I've learned through experience. If there's an FAQ of common problems when building C extensions, it belongs there.

While this functionality sounds nice in principle, it only really works if something also adds the directory to *look* for the library to the link line as well. But if you can get *that* to the link line, you may as well just add the ".lib" to the link line directly and not send the linker on a wild goose chase based on a header. In addition, nothing ties "find python.lib" to the one that actually goes with the header that's telling it to be found either, so you can get the wrong one too (probably not so much an issue for Python now that ABI flags are gone, but it's still a thing).

Due to these behaviors and the lack of a link directory pragma (not that you could write a relocatable one in C preprocessor anyways), I find `#pragma comment(lib)` to just be a misfeature more than anything.
History
Date User Action Args
2022-04-11 14:59:22adminsetgithub: 82909
2020-05-12 23:29:17mathstufsetmessages: + msg368749
2020-05-12 22:21:00steve.dowersetmessages: + msg368744
2020-05-08 21:58:03Jean-Christophe Fillion-Robinsetmessages: + msg368474
2020-04-27 19:19:03python-devsetkeywords: + patch
nosy: + python-dev

pull_requests: + pull_request19062
stage: patch review
2019-11-14 21:18:09mathstufsetnosy: + mathstuf
2019-11-11 15:46:43Jean-Christophe Fillion-Robinsetmessages: + msg356365
2019-11-09 22:53:37steve.dowersetmessages: + msg356310
2019-11-06 22:41:31Jean-Christophe Fillion-Robincreate