[CMake] Project dependencies

[Alexander Neundorf]

On Monday 19 April 2010, Benjamin Eikel wrote:
> Hello Alexander,
>
> Am Sonntag, 18. April 2010 10:52:17 schrieb Alexander Neundorf:
> > Hi Benjamin,
> >
> > On Friday 16 April 2010, Benjamin Eikel wrote:
> > > Hello,
> > >
> > > maybe my first post was not clear enough.
> > > I created a minimal example to demonstrate what I mean (see attached
> > > files). That example contains a library called MyLib and a binary
> > > called MyBin. The enclosed shell script can be used to build the binary
> > > on Linux. At first the library will be configured such that the file
> > > "MyLibConfig.cmake" will be created. After that the binary will be
> > > configured and a build will be started. The build will fail because the
> > > library was intentionally not build before. After that another way of
> > > including the library is used. The second "CMakeLists.txt" file uses
> > > add_subdirectory to reference the library.
> >
> > Yes, that's the normal way to do it.
> >
> > > When issuing a make command now,
> > > the library will be built automatically. My question is if it is
> > > possible to achieve this behavior when using the approach mentioned
> > > first. This would make things easier in our projects when there are
> > > multiple dependencies to different libraries which will be changed
> > > often and a build of the binary should be triggered automatically.
> >
> > The normal and recommended way to to add all that (via add_subdirectory)
> >  into one CMake project. What is speaking against this in your case ?
> >
> > If you really want to have it separated, you may try how far you can get
> >  with externalproject_add(), but I would assume that the straightforward
> >  approach (add_subdirectory) will work much better.
>
> I think you are right.
> But I still want to build the libraries on their own (because they are used
> in some Hudson builds to check if the build works correctly). Therefore a
> library libA depending on another library libB calls find_package(libB) to
> find the needed files.
> When using the add_subdirectory() approach I currently have the problem
> that the find modules do not find the library libB (because it has not been
> build yet). Is it the right way to integrate a check for the target libB
> like the following into FindlibB.cmake?
>
> if(TARGET libB)
> 	set(libB_LIBRARY Geometry)
> else()
> 	find_library(libB_LIBRARY
> 		NAMES libB
> 		HINTS ${libB_PKGCONF_LIBRARY_DIRS} [...]
> 		PATH_SUFFIXES lib64 lib [...]
> 	)
> endif()
>
> This seems to work if I call add_subdirectory() in the correct order in the
> top-level project.

Yes, something like this can work.

Alex