Cached executables are not executable

Thanks a lot for the action, it’s been a pleasure to use!

We’re using the cache to store some precompiled Haskell artifacts, which include executable files. On Linux everything seems to be running smoothly, but from time to time the macOS build cache seems to get corrupted. Here’s an example:

1. A new PR triggers a CI run. For some reason the cache didn’t work out (not a big deal), so the artifacts get recompiled. The executables get used in the later stages of the run, so they had to be built correctly.
2. An update to PR is pushed, triggering another run. This one no longer rebuilds from scratch, but it almost immediately fails with the following error (~/.stack is part of the cache):

/Users/runner/.stack/setup-exe-cache/x86_64-osx/Cabal-simple_mPHDZzAJ_2.4.0.1_ghc-8.6.5: /Users/runner/.stack/setup-exe-cache/x86_64-osx/Cabal-simple_mPHDZzAJ_2.4.0.1_ghc-8.6.5: cannot execute binary file

I’ve been trying to debug this issue, but I’m running out of ideas for what might be going wrong. Is it possible that the macOS runners are using different CPU architectures? Is executable caching supported?

[dhadka]

It sounds like this might be related to a few other reported issues of corrupted executables on MacOS. As far as I an tell, the corruption is caused by BSD tar. No idea why, but the problem seems to go away when switching to GNU tar. See https://github.com/actions/cache/issues/460#issuecomment-728366594 for the workaround.

[apaszke]

@Martinsos we’re doing the same thing in our repo. Fortunately in this case it doesn’t cost us much because the setup executables are small, but I’m afraid that it might hint at a larger problem with this action.