[OE-core] cmake.bbclass questions

[Matt Madison]

On Wed, 2015-02-11 at 11:21 +0100, Stefan Herbrechtsmeier wrote:
> Am 10.02.2015 um 23:53 schrieb Matt Madison:
> > I just finished some recipes for some CMake-built packages (from the 
> > Kurento project).  I managed to get everything building, but I had to 
> > modify how cmake.bbclass does things, and I'm wondering if there's a 
> > better way to solve some of these.
> >
> > Each of the packages generates a pkg-config file and a CMake module 
> > that are then used by other packages (later in the build) to locate 
> > their dependencies.  I see that cmake.bbclass hard-codes the 
> > CMAKE_MODULE_PATH setting to point to just the location in the native 
> > sysroot, but target packages can't install their CMake modules there.  
> > I tweaked the definition so that when building non-native packages, 
> > CMAKE_MODULE_PATH points into both the target sysroot and the native 
> > sysroot.  This seemed to do the trick, but wasn't sure it was the 
> > correct way to solve this.
> Instead of a CMake module the project should install a 
> <Name>Config.cmake in its data directory and append a private module 
> directory to the CMAKE_MODULE_PATH.

Ah, OK. Is that the typical pattern for CMake-based packages?  

> 
> > The generated pkg-config files were a bit trickier - the CMakefiles 
> > that generate them assume that the CMAKE_INSTALL_xxxDIR variables are 
> > always relative paths, but cmake.bbclass passes in absolute paths -- 
> > which, by my read of the CMake docs, is allowed.  I think in this case 
> > the Kurento CMakefiles need fixing, but there were a lot of them, so 
> > it was simpler to change cmake.bbclass to strip the prefix off the 
> > front of those variable settings.
> CMake supports relative and absolute paths for the CMAKE_INSTALL_xxxDIR 
> variables but the default are relative paths.
> 
> The CMake files sould be fixed and extract the relative path from the 
> full path variable:
> file (RELATIVE_PATH CMAKE_INSTALL_RELATIVE_LIBDIR 
> "${CMAKE_INSTALL_PREFIX}" "${CMAKE_INSTALL_FULL_LIBDIR}")

Great, thanks, I'll suggest that to them.

Regards,
-Matt