FindQt4 and other CMake module duplication

[Alexander Neundorf]

On Wednesday 08 July 2009, Andreas Pakulat wrote:
> On 08.07.09 16:08:10, Mike Arthur wrote:
> > 2009/7/8 Andreas Pakulat <apaku at gmx.de>:
> > > That usually happens when there are bugs in the FindXXX modules in
> > > cmake, in particular in the cmake version we require (current 2.6.2 I
> > > think). Or if the cmake version we require doesn't ship a suitable
> > > FindXXX module we need.
> > >
> > > If you are sure that switching to the one coming with the minimum
> > > required cmake doesn't cause any bugs, then sure.
> >
> > Ok, I'd be tempted to go down this route. How sure do I need to be? Is
> > it sufficient to try and remove it and see if I can still do a clean
> > build on 2.6.2 and 2.6.4 (the most recent)?
>
> If "clean build" means all of KDE svn (well, at least extragear I think),
> then I guess yes. Please make sure to also test things like installing
> kdelibs and all the modules into separate prefixes.

We require 2.6.3, so you must compare the modules we have with the ones 
shipped with cmake 2.6.3.
I'm not aware of any modules which are really easy to remove (I'm sure FindQt4 
is not one of them).
In general this means if we want to remove one of ours, first we have to merge 
the modifications we did into the ones in cmake, wait until a cmake version 
is released with these modified modules, and then increase the minimum 
required cmake version for KDE.
Increasing the required cmake version for KDE is a big step and needs serious 
arguments.
My impression is that we should be able to stay with 2.6.3 also for KDE 4.4.

> > >> If not, can these be updated to
> > >> the latest versions from CMake after each CMake release?
> > >
> > > You can merge in relevant changes, sure, they're writeable by anyone.
> > > However you need to make sure to use only features which are available
> > > in the minimum required cmake version.
> >
> > Again, I think this leans towards the approach of deleting our stuff
> > that's duplicated in the minimum version of CMake we support.
>
> Right, but you need to study the files and be aware of possible
> side-effects. Basically you can only remove a file if its 100% the same
> code.

More or less, yes.

Alex