I think I am looking at this from a different viewpoint than is mentioned here. First, I always leave warnings on in production. I used to make changes between "production" and "non-production" code and later realized how easy it is to miss those changes. So I don't change 'em. If anything, I use config files for those differences.

So what happens when I leave warnings enabled? For one of our applications, we get huge error logs. They are completely ignored until a problem occurs, then we waste a lot of time trying to narrow down which of the entries might match our problem.

I'm working on a new version of this application and one of my goals is to completely eliminate warnings. So far, I've had a test version of the new app running for a month and the only entries in the error log are bad login attempts -- exactly what I wanted. If an app generates spurious warnings, it is crying wolf and programmers will be conditioned to ignore them. If all warnings are eliminated, it makes you sit up and take notice on the rare occassions when one does occur.

One of our shop standards is that all code must run clean under warnings. Follow that standard, leave the warnings on, and if you see something in your logs, there's a very good chance that you really do have a problem.

Cheers,
Ovid

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