I realized that our C++ unit tests were failing on my newer MacOS (12.1). Took me a while to figure out that it was simple "cout" and "cerr" print statements that were causing the failures. Finally figured out that the standard C++ library was not being automatically linked. This seems to be a Bazel issue. Luckily there is a fix and it is in newer versions of Bazel (4.2.2 and 5.0).
I have a PR here ready for review to bump the version of Bazel. https://github.com/apache/incubator-heron/pull/3764 Nick
