I’ve been one of the people who used GCC 5 for a long time.
With recent cuda (I’m currently on 9.2) supporting newer GCC I had switched to 6 and this week (because I had trouble with MKLDNN’s use of -werror) to gcc 7.
For my (CPU only) laptop, I always use the default compiler of Debian/unstable, currently gcc 8.2.0.
Best regards
Thomas