compilation errors on catalina-xcode

[tlambert03]

I'm not exactly sure what's happening here, but we're seeing C-compilation errors (unable to find libcpp.algorithm) on the new catalina-xcode container that we did not see on mojave.

warning: include path for stdlibc++ headers not found; pass '-stdlib=libc++' on the 
command line to use the libc++ standard library instead [-Wstdlibcxx-not-found]
c-blosc/internal-complibs/snappy-1.1.1/snappy-stubs-internal.cc:29:10: fatal error: 
'algorithm' file not found
#include <algorithm>

(full task here https://cirrus-ci.com/task/6660339609632768?command=pip#L387-L455)

This occurs while building numcodecs on mac, but only with python 3.6, so I assume their sdist may also be playing a role here? or perhaps its the only one in our dependencies that exposes the issue.

this should be sufficient to replicate:

task:
  name: macos 3.6 catalina
  osx_instance:
    image: catalina-xcode
  setup_script:
    - curl https://repo.continuum.io/miniconda/Miniconda3-latest-MacOSX-x86_64.sh > install.sh
    - bash install.sh -b -p $HOME/conda
    - conda install --yes -c conda-forge setuptools
    - conda install -yn base conda=4.8.1  # 4.8.2 completely breaks py3.6 at the moment
    - conda install -y python=3.6
    - pip install zarr

I am trying to fix this on my own, maybe by adding something to includes? but figured I would mention it in case there is a more general catalina thing that might be useful to include by default in the osx container... thanks.

[tlambert03]

just wanted to add, for anyone who may come across this issue, adding:
- export MACOSX_DEPLOYMENT_TARGET=10.10 before the pip install command solved this for me.

I suspect that's not something that should be modified on a global container level, so closing this issue.

[fkorotkov]

@tlambert03 glad you found it! I was also researching the problem in the meantime. Will note it for future researchers. 🙌

[tlambert03]

thanks for looking into it!