Support CMake-Version-Variables

[Andreas Pakulat]

On 15.08.08 00:13:49, Alexander Neundorf wrote:
> On Thursday 07 August 2008, Andreas Pakulat wrote:
> > On 07.08.08 22:11:11, Thiago Macieira wrote:
> > > Andreas Pakulat wrote:
> > > >This has a problem, I can't depend on KDE 4.2.0 until its released and
> > > >hence modules in trunk/ cannot have a dependency on kdelibs from trunk/
> > > >
> > > >For example kdevplatform now has a hard dependency on kdelibs from
> > > >trunk/, so what I need is require KDE >= 4.1.60 (current version used in
> > > >trunk/) not 4.2.0 as that doesn't exist yet and 4.1.0 doesn't work
> > > >anymore.
> > >
> > > Right, sorry. I hadn't thought of pre-releases.
> >
> > Thanks for doing the logic-thinking for me :) Patch attached, it uses a
> > negation of your pseudo-code to avoid having to create new variables.
> >
> > Andreas
> 
> Looks good from the technical side.
> Still there is one thing:
> right now the way to specify the required KDE version is to set the 
> KDE_MIN_VERSION variable before calling find_package(KDE4).
> 
> This patch now adds a second way how to specify the required version.
> Pro:
> -this is how find_package() now supports specifying the minimum version 
> number, i.e. in some way the officially recommended way

Another pro is that we don't have to take care of moving a whole block
(variable-setting+find_package) when reorganizing a module's
CMakeLists.txt. 

> Con:
> -with the patch there are now two ways how to do the same thing (and the old 
> way has to stay, in order to stay source compatible)

Well, while I agree its better to leave it in, the variable isn't
documented and hence is IMHO an internal variable - bound to change at
any time. Just like in code anything that has no api dox is bound to
change at any time.

> -several other modules also support FOO_MIN_VERSION or similar variables, so 
> using such a variable is currently kind of de-facto standard for specifying 
> the minimum version.

Well, I think those modules support a version variable only because
there was no other way until now. If we'd always just stay with what we
have we'd never make any progress at all :) 

So to conclude: I don't think the two con's weigh heavy enough not to
apply the patch.

Andreas

-- 
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