On gcc 7 the new -Wimplicit-fallthrough option was introduced which produces warnings about switch cases that can fall through.

The easiest way to silence these warnings is to add the comment /* Falls through. */ for those cases. More information here [0]

Attaching the stderr output from compilation from the master branch.

[0] https://developers.redhat.com/blog/2017/03/10/wimplicit-fallthrough-in-gcc-7/