Why change warning level of a specific warning in C++?

Question

Visual C++ features #pragma warning that among other things allows to change the warning level of a specific warning. Say warning X has level 4 by default, then after

#pragma warning( 3, X )

it will have level 3 from that point.

I understand why I would temporarily disable a warning, turn a warning into an error or turn on a waring that is off by default. But why would I change a warning level?

I mean warning level of a specific warning works together with the compiler "warning level" option /W, so I currently can't imagine a setup in which I would want to change a level of an individual warning since the warning being emitted or not will depend on the project settings.

What are real-life examples of when I really need to change a warning level of a specific warning in C++?

Answer 1

When you want to run on level 3 or 4, but you want to see/not see a specific message, you can change its level. Sure, the pragma might have no effect if the warning level isn't what you think, but that's life with pragmas.

Answer 2

It is much easier to take the one or two level 4 warnings you want detected and use the pragma to bring them into level 3 than it is to use /W4 and disable (/Wd####)the all the warnings you don't care about.