gh-99948: Support ctypes.util.find_library in emscripten environment

[ryanking13]

This PR adds ctypes.util.find_library support in Emscripten environment. I am resubmitting the patch that was closed around 3 years ago (#99950).

The previous pull request was closed at that time, as CPython did not have an official Emscripten build. But now it is back to tier-3 with buildbot support, so I think it makes sense to support this in CPython Emscripten builds.

Pyodide is applying this patch to support packages that rely on ctypes.util.find_library to locate packages.

• Issue: ctypes.util.find_library support on WASM platforms #99948

[ryanking13]

!buildbot emscripten

[bedevere-bot]

You don't have write permissions to trigger a build

[hoodmane]

!buildbot emscripten

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @hoodmane for commit 857b0fa 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F138519%2Fmerge

The command will test the builders whose names match following regular expression: emscripten

The builders matched are:

• WASM Emscripten PR

[freakboy3742]

A couple of comments/suggestions about the implementation and testing strategy.

I'd also like @hoodmane to confirm the emscripten details on this; this all makes sense assuming LD_LIBRARY_PATH exits in the environment - but my understanding was the there were very limited opportunities to actually manipulate environment variables in a runtime environment.

It's entirely possible I'm missing something here - and the fact this patch comes from Pyodide suggests I might be - I just want to make sure I understand the full context here, and this isn't encoding as Pyodide-ism that won't necessarily apply elsewhere.

[bedevere-app]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[ryanking13]

I'd also like @hoodmane to confirm the emscripten details on this; this all makes sense assuming LD_LIBRARY_PATH exits in the environment - but my understanding was the there were very limited opportunities to actually manipulate environment variables in a runtime environment.

The runtime environment might not have LD_LIBRARY_PATH. If it doesn't, it will simply fail to locate the library, but if it does, it can be used to locate the library from a specific location. Emscripten utilizes LD_LIBRARY_PATH in their dlopen implementation, so I think it makes sense to use the same approach.

I think this is a general approach that can be used in other non-Pyodide environments. We've noticed that a few packages use ctypes.util.find_library (example1) to locate and load shared libraries. Any Emscripten-targetting Python runtimes that want to support those packages should provide a way to support this function.

[hoodmane]

LD_LIBRARY_PATH exists and works as expected.

[freakboy3742]

!buildbot Emscripten

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @freakboy3742 for commit ff6a669 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F138519%2Fmerge

The command will test the builders whose names match following regular expression: Emscripten

The builders matched are:

• WASM Emscripten PR

[freakboy3742]

!buildbot emscripten

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @freakboy3742 for commit 8157604 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F138519%2Fmerge

The command will test the builders whose names match following regular expression: emscripten

The builders matched are:

• WASM Emscripten PR

[freakboy3742]

One very cosmetic suggestion, but otherwise this looks good to me - thanks for the patch!

[miss-islington-app]

Thanks @ryanking13 for the PR, and @freakboy3742 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-139022 is a backport of this pull request to the 3.14 branch.

[ryanking13]

Thanks!