Fails to compile; __attribute((fallthrough)) requires GCC 7
__attribute((fallthrough)) used in libs/container/hashfunc.h
requires GCC 7. Older GCC fails to compile; GCC 4.9 in my case on Debian Jessie. It was added in commit 951a604c.
Should be able to replace it with "fall through" comments or add a custom macro only defined to __attribute((fallthrough)) if GCC 7+ (what about Clang?). (GCC 4.9 doesn't report a warning here so I can't easily test silencing warnings using comments.)