As a company you can decide where to fall on this scale, I applaud you for -Wall'ing but for most it's too much, the important thing is to make sure that everyone has agreed which warnings are acceptable and you refuse code that violates that.
We're using PHP (so runtime warnings, instead of compiler issues) but we have a zero-error policy, if anything raises a warning or error we refuse to merge (or ticketize fixing since a bunch of stuff is legacy and we're still paying it down).