Re: Detect unused header files?

[Sam Ravnborg <sam@ravnborg.org>]

On Tue, Jul 28, 2009 at 01:36:26PM -0700, Christopher Li wrote:
> On Tue, Jul 28, 2009 at 11:18 AM, Sam Ravnborg<sam@ravnborg.org> wrote:
> > In the kernel we would like to avoid all
> > unused include files.
> > Especially in the headers we export to userspace.
> >
> > Are there any easy way we can use sparse to detect
> > that a specific header file is not used?
> 
> I don't know a way to do that with current sparse.
> We can implement some code for this.

Would be great...
If you can give some general into I can maybe give
it a shot albeit I have only very limited sprase
hacking knowledge.

> 
> We need to have a good definition of what is used.

The short version...
The header file that include the file is dependent
on the included file.

So if we:
- use (check/test/reference) a macro from the file => used
- use a typedef/struct
- ...
then we need the included header file.

> 
> > The header files I have in mind will be fully self-contained
> > as they all include the header files they need to be used.
> 
> But a lot of case we have the header file is used in *another*
> file.
We do not care about this case...

The objective is to get the exported kernel headers as lean as possible.
This may occasionally break userland - but until now this has
been manageable.


If we apply this to kernel internal headers then we need to
do a bit of test builds to check things.
This is the same thing we do when we untange the include mess we have
today so we know what to do.
-next is btw a great help here.

If we do this inside spase or using a dedicated backend is not so important.
But adding this as a default=disabled option to sparse would be preferred.

	Sam