Criteria for a warning to be in -Wall? (was: Re: a warning to implement)

[Tim Hollebeek]

> As an aside, I'm a bit surprised to see that far more misleading
> constructs should be warned about by GCC, but the corresponding flags
> are not turned on by -Wall and yet nobody is arguing so strongly about
> having them in -Wall.  An example is -Wnested-externs.  

Let's discuss what the conditions should be for a warning to be in
-Wall, and then document it.  If that ends up meaning -Wnested-externs
should be added, so be it.

-Tim