When I write my own code I turn on as many compiler warnings as I can, and make sure it compiles clean. If there were more warnings I'd turn them on.
Problem is usually third party libraries. Plenty of open source projects don't give a single shit about compiler warnings and unsafe practices. So if I include a header from libSomething package, here come 10k warnings. I remember one project (don't remember which one) specifically said in its documentation something like "don't submit patches to fix compiler warnings, it's impossible to keep up with every complaining compiler out there." With programmers like that out there, what hope do we have?
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wfoo"
#pragma GCC diagnostic pop
(Despite the "GCC" moniker, Clang supports the same approach.)