Conda should use newer (the newest?) OSX SDK for building

[rggjan]

Please see the discussion here:
conda-forge/pyside2-feedstock#46 (comment)

Conda-forge currently builds against the OSX SDK 10.9. This causes issues for example with Qt + Pyside2, which requires both Qt and python to be built with OSX SDK 10.14 or 10.15.

I understand that Conda-forge builds against SDK 10.9 to be backwards compatible to that version of OSX. However, this is also possible with building against the newest SDK (10.15), and the setting the deployment target to a lower OSX version, like 10.9.

Here again the details:

Where did you read this? That's not how how SDKs work. You build with 10.12 and it will run on 10.14, not the other way around.

See on developer.apple.com:

It works both ways on OSX.

In the example of the link I posted, they build with base SDK 10.6 and run on 10.4 and newer. If the code doesn't use any of the newer API's (not existing in 10.6) this works out of the box. If the code wants to use new 10.5 or 10.6 API's on supported operating systems, the code must first check the OS version before using the API's. Which I guess Qt does, when they say on their official docs that compiling against the 10.14 SDK and then running on 10.12 works fine...

So Apple recommends always using the newest SDK, and then setting the Deployment target to the lowest OSX version you want to support...

[CJ-Wright]

xref: conda-forge/conda-forge.github.io#891

[scopatz]

Yep, I believe that this is a duplicate

[isuruf]

It's not. conda-forge/conda-forge.github.io#891 is about packages with a requirement on newer MACOSX_DEPLOYMENT_TARGET (like 10.12). This issue is about packages with a requirement of a newer SDK, but with the same lower MACOSX_DEPLOYMENT_TARGET (like 10.9) that uses weak linking.

[scopatz]

In that case it seems like it should be moved to the conda-forge/conda-forge.github.io repo

[isuruf]

This is where the code lives, but I'm fine with either.

[scopatz]

Oh ok, nm

[rggjan]

Is there any timeline on this issue? Any way I can help?

[isuruf]

@rggjan, it looks like we can't enable this globally, but we can have an option to enable per feedstock. Issue is that most autotools based packages would check whether functions exist and using a newer SDK would make them available even if they are weak symbols. (For eg: clock_gettime is in 10.12, but autotools detects it even if target is set to 10.9 if the SDK is 10.12 or higher)

[rggjan]

I see, thanks. That makes sense.

Would it be possible to enable it for the python feedstock? As this would fix the original issue of PySide2/Qt being broken?

Should I create a separate issue for this?

[isuruf]

I suggest changing the logic at https://github.com/conda-forge/conda-forge-ci-setup-feedstock/blob/master/recipe/run_conda_forge_build_setup_osx#L9-L27 to use 10.15 as the SDK if there's a variable like WITH_LATEST_OSX_SDK instead of using MACOSX_DEPLOYMENT_TARGET for the SDK version. Then we can have that variable enabled in the python-feedstock.

[rggjan]

Sounds like a good plan! However, it should be in addition to MACOSX_DEPLOYMENT_TARGET, I think. We might want to use the latest sdk, but still set MACOSX_DEPLOYMENT_TARGET to 10.9, for example, if we want the built executable to be able to run on OSX 10.9...

[rggjan]

Any updates on this? Or is there at least a way to do the same as in bioconda/bioconda-recipes#21180 and use a newer SDK for python to fix conda-forge/pyside2-feedstock#46?

[isuruf]

@rggjan, see my comment at #67 (comment). PRs are welcome.

[rggjan]

Thanks a lot @psavery @isuruf!

What needs to happen to rebuild python 3.7 on OSX with these changes, so PySide2 actually works on OSX? (conda-forge/pyside2-feedstock#46)

(Sorry, I'm not very familiar with the conda CI / building pipeline)

[cjh1]

@rggjan I think we need to raise an issue with python-feedstock, to see if they are prepared to accept setting WITH_LATEST_OSX_SDK.

[psavery]

@rggjan I put up an issue for it on the python feedstock. It is conda-forge/python-feedstock#365

[rggjan]

Perfect, thanks @psavery!

Would it make sense to do this for qt and/or PySide2 as well?

[cjh1]

I think PySide2 is already be build with a newer SDK.

[rggjan]

@cjh1 How do you know?

[cjh1]

@rggjan May be not, I thought this one had been merged, but apparently is was closed. In our testing we only needed to rebuild python.