[CMake] Project dependencies

[Benjamin Eikel]

Hello Alexander,

Am Montag, 19. April 2010 um 18:03:28 schrieb 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.
I implemented it this way and it works like a charm. Thank you for your input.

Kind regards,
Benjamin