I saw this first time many years ago. It clearly states that exceptions is a good thing but shouldn't be used in Google's projects because their code is not prepared for exceptions:

> On their face, the benefits of using exceptions outweigh the costs, especially in new projects. However, for existing code, the introduction of exceptions has implications on all dependent code. If exceptions can be propagated beyond a new project, it also becomes problematic to integrate the new project into existing exception-free code. Because most existing C++ code at Google is not prepared to deal with exceptions, it is comparatively difficult to adopt new code that generates exceptions.

And most importantly, I don't think that they're disabling exceptions using compiler flag. I'm sure that they just using error codes for error handling instead of exceptions.