bazel build //:clotestbin-cc fails with .../copy-closure: paths["$lib"]: unbound variable

[hofbi]

Describe the bug
Fresh bazel build //:clotestbin-cc fails

To Reproduce

• Clone the repo
• Install the requirements
• cd tests
• bazel build //:clotestbin-cc

Expected behavior
The target is corecctly built

Environment

• OS name + version: Ubuntu 20.04
• Version of the code: Latest master

Additional context

WARNING: Option 'host_javabase' is deprecated
WARNING: Option 'host_javabase' is deprecated
INFO: Analyzed target //:clotestbin-cc (0 packages loaded, 0 targets configured).
ERROR: ~/clodl/tests/BUILD:109:15: Action clotestbin-cc-closure.zip failed: (Exit 1): bash failed: error executing Action command (from target //:clotestbin-cc-closure) /bin/bash -c ... (remaining 4 arguments skipped)

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
bazel-out/k8-opt-exec-ST-879f06706572/bin/external/io_tweag_clodl/copy-closure: line 76: paths["$lib"]: unbound variable
Target //:clotestbin-cc failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 0.321s, Critical Path: 0.07s
INFO: 2 processes: 2 internal.
ERROR: Build did NOT complete successfully

[aherrmann]

The build succeeds for me if I use the Nix shell

$ nix-shell ../shell.nix --run 'bazel build //:clotestbin-cc'

Without Nix I observe

ERROR: /home/aj/tweag.io/clodl/tests/BUILD:109:15: output 'scanelf' was not created
ERROR: /home/aj/tweag.io/clodl/tests/BUILD:109:15: Action bash failed: not all outputs were created or valid
Target //:clotestbin-cc failed to build

[hofbi]

Using the nix shell, it works for me as well. Is this how people should use this? Should we update the README here?

[facundominguez]

Thanks for the report, @hofbi.

bazel-out/k8-opt-exec-ST-879f06706572/bin/external/io_tweag_clodl/copy-closure: line 76: paths["$lib"]: unbound variable

This looks like a bug. It would need to be investigated why paths is undefined for the given lib, before deciding a remedy. This is the location of the failure. paths maps library names to their paths, and it is computed by calling to ldd. The missing $lib is coming from the needed array, which is computed by scanelf.

ERROR: /home/aj/tweag.io/clodl/tests/BUILD:109:15: output 'scanelf' was not created

I can reproduce this in the nix-shell if I remove pax-utils from the dependencies. Which hints to me that this is caused by scanelf being missing from the path. This is mentioned as a requirement in the readme, but I'd expect the build to fail in a more telling way when scanelf is missing, so it would be another thing to improve. I think the error comes from executing this action.