[cmake-developers] Support for imported targets in CMAKE_REQUIRED_LIBRARIES

[Alexander Neundorf]

On Thursday 19 January 2012, Brad King wrote:
> On 1/18/2012 4:24 PM, Alexander Neundorf wrote:
> > On Wednesday 18 January 2012, Alexander Neundorf wrote:
> >> Hi,
> >> 
> >> the variable CMAKE_REQUIRED_LIBRARIES is used by several of the
> >> check-modules for listing additional libraries which should be linked.
> >> It is common to use variables set by Find-modules for this, e.g.
> >> set(CMAKE_REQUIRED_LIBRARIES ${JPEG_LIBRARIES} )
> >> 
> >> Now, if the module did not simply set JPEG_LIBRARIES to the full path,
> >> but instead created an imported target, e.g. FindJPEG::libjpeg, this
> >> leads to a problem.
> >> The check-modules will simply append this to the linker command, so
> >> there will be -lFindJPEG::libjpeg, which will not work.
> >> This actually happened in KDE the first time more than 2 years ago.
> >> 
> >> On cmake stage there is now a branch
> >> HandleTargetsInCMakeRequiredLibraries, where I ported the solution from
> >> KDE to CMake and applied it to all places where
> >> CMAKE_REQUIRED_LIBRARIES is used.
> >> I did not test it yet (but it should work, since it is exactly the same
> >> as in KDE).
> >> 
> >> Please have a look at it.
> > 
> > It's here:
> > http://cmake.org/gitweb?p=stage/cmake.git;a=log;h=refs/heads/HandleTarget
> > sInCMakeRequiredLibraries
> 
> When inspecting the IMPORTED_CONFIGURATIONS, rather than choosing the first
> one might you honor CMAKE_TRY_COMPILE_CONFIGURATION?

Yes, I wasn't aware of this.
 
> Does it handle link-interface libraries recursively?

Yes, it should (but not tested extensively).
 
> I think a full solution to this will end up duplicating a lot of the logic
> that CMake already has in its C++ code for link dependency analysis.  I
> wonder if instead you could modify the signature of try_compile to accept
> the LINK_LIBRARIES as a formal argument.  Then teach the C++ code to
> resolve the imported targets and take care of the link interfaces.

I'll have a look at that too.
What things exactly do you have in mind additionally ?

Alex