[CMake] FindBoost.cmake from 2.6

[Andreas Pakulat]

On 03.07.08 12:23:11, Doug Gregor wrote:
> On Tue, Jul 1, 2008 at 1:24 PM, Fernando Cacciola
> <fernando.cacciola at gmail.com> wrote:
> > (7)
> >
> > I couldn't understand the dicotomy between the cached and non-cached
> > versions of the include dirs:
> >
> > Boost_INCLUDE_DIRS vs Boost_INCLUDE_DIR
> >
> > What's the choice for? What doesn't the library dir, or for that matter, the
> > libraries list offer the same choice?
> 
> I actually don't know why this is the why it is, sorry.

I'll try to read the rest later and answer everything, but for now just
this: The module needs to be fully backwards compatible to the CMake 2.4
version (thats why it was included in 2.6.0), and in cmake 2.4 you had
only 2 variables, one for include dirs one for library dirs and did
something like

link_directories( ${Boost_LIBRARY_DIRS} )
target_link_libraries( foo boost-thread )

Andreas

> > (9)
> > It is documented that this requires CMake 2.5 (which is 2.6 for us end
> > users). And later overdocumented that this ships with CMake 2.6 so the
> > version is always right.
> >
> > Well, strictly speaking one can use *this* module with earlier cmake
> > versions, such as 2.4.7 which is still largely used in many linuxes, by
> > emulating the additional find_package feautres.
> > That is, instead of calling it like:
> >
> > find_package(Boost 1.37.1 COMPONENTS thread )
> >
> > call it like this:
> >
> > set( Boost_FIND_VERSION 1.37.1 )
> > set( Boost_FIND_VERSION_MAJOR 1 )
> > set( Boost_FIND_VERSION_MINOR 37 )
> > set( Boost_FIND_VERSION_PATCH 1 )
> > set( Boost_FIND_COMPONENTS thread )
> >
> > find_package(Boost)
> >
> > which works just the same with the old find_package (this is in fact what
> > I'm doing in CGAL to avoid requiring users to install CMake 2.6 which is
> > usually not just a simple apt-get/rmp call in many linuxes)
> 
> I'm not quite sure what to do about this... with the FindBoost we ship
> in CMake 2.6.1, we should take advantage of CMake's features (e.g.,
> the new HINTS feature, which eliminates a bunch of redundant code).

The reason its so backwards compatible is that I wanted to be
kdevplatform's (kde module) copy to be as similar as possible (and that
one needs to work with cmake 2.4) so that later when KDE depends on
CMake 2.6 I'll have to do as little porting of our find-boost-code as
possible.

> Should we maintain a separate version of FindBoost for older versions
> of CMake? I don't know, but I'm concerned about the maintenance burden
> there, particularly for a complicated module like this one.

IMHO no, the one included with cmake 2.4 works ok'ish and cmake never
supported using a FindXXX.cmake from a newer version with an older
version of cmake.

Andreas

-- 
Chicken Little only has to be right once.