[CMake] Absolute Path linking library

Wed Sep 4 12:02:55 EDT 2013

Thank you for you help Clint.

I actually relinked, but as you said I still had the LINK_DIRECTORIES.
However, if I remove it, I have a linking error telling me it cannot find
the library.

Should I keep the library in Target_Link_Libraries, or with new flags,
dependency will automatically find the library ?

Thank you.
-Laurent

On Wed, Sep 4, 2013 at 11:59 AM, Clinton Stimpson <clinton at elemtech.com>wrote:

> On Wednesday, September 04, 2013 11:53:45 AM Laurent Chauvin wrote:
> > Hello,
> >
> > I just tried to set the MACOSX_RPATH 1 in the top CMakeLists of MyLib,
> and
> > when I now do otool -L libMyLib.dyld, I can indeed see
> @rpath/libMyLib.dyld.
> > However, my executable "MyExample" is still not able to find the library
> at
> > runtime. When I do otool -L MyExample, I still have libMyLib.dyld, not
> > @rpath/libMyLib.dyld.
>
> Did you relink MyExamle against the new libMyLib.dylib?  CMake doesn't
> modify
> the install names of libraries being linked against, so if otool -L
> MyExample
> still gives "libMyLib.dylib", I'm assuming you didn't relink it.  Using a
> cmake generated export file would take care of setting up dependencies so
> the
> relink would happen simply by doing a make.  If you use LINK_DIRECTORIES,
> you
> miss the relink dependency.
>
> Clint
>
> > And I have same error (Library not loaded, image not found) when trying
> to
> > start the example.
> >
> > Should I add something more (or remove something) from my CMakeLists
> > example ?
> >
> > I'm sorry I'm not really familiar with these mechanisms.
> >
> > Thank you very much.
> > -Laurent
> >
> >
> > On Wed, Sep 4, 2013 at 11:30 AM, Laurent Chauvin
> >
> > <lchauvin at bwh.harvard.edu>wrote:
> > > Thank you very much for your answer.
> > >
> > > I will try to use the MACOSX_RPATH.
> > >
> > > However, I have some questions. As the flag suggests, it's only for
> mac.
> > > Is there anything similar for Linux (and eventually Windows systems) ?
> > >
> > > Also, the problem to set the full path of the library is, if I compile
> on
> > > Windows the extension of library will be dll, on Mac it will be dyld,
> and
> > > .a on linux.
> > > I could make a condition to set the extension at the end of the name of
> > > the library like libMyLib.(dll, dyld, a) but, I feel like it's not
> really
> > > a
> > > clean way to do it.
> > >
> > > Is there a better way to do it ?
> > >
> > > Thank you very much.
> > > -Laurent
> > >
> > > On Wed, Sep 4, 2013 at 10:57 AM, Clinton Stimpson
> <clinton at elemtech.com>wrote:
> > >> On Tuesday, September 03, 2013 09:47:45 PM Laurent Chauvin wrote:
> > >> > Hello everyone,
> > >> >
> > >> > I'm working on a library, and I would like the users be able to
> create
> > >>
> > >> their
> > >>
> > >> > own program and liking to my library (by specifying path in cmake).
> > >> >
> > >> > I created the library and an example to test it.
> > >> > Everything compiles.
> > >> >
> > >> > However, when I try to run my example I have this error:
> > >> >
> > >> > MyExample:
> > >> >       libMyLib.1.dylib (compatibility version 1.0.0, current version
> > >>
> > >> 1.0.0)
> > >>
> > >> >       /usr/lib/libstdc++.6.dylib (compatibility version 7.0.0,
> current
> > >>
> > >> version
> > >>
> > >> > 56.0.0) /usr/lib/libSystem.B.dylib (compatibility version 1.0.0,
> > >> > current
> > >> > version 169.3.0)
> > >> >
> > >> > The problem is my example is not in the same directory as my library
> > >>
> > >> (not
> > >>
> > >> > even in a subdirectory). And it seems it's linking to my library
> with a
> > >> > relative path.
> > >> >
> > >> > If I add the path of my library in DYLD_LIBRARY_PATH it works, but I
> > >>
> > >> would
> > >>
> > >> > like the users to be able to compile and link straight forward.
> > >> >
> > >> > To link the library to my example I use find_package(MyLib REQUIRED)
> > >> > and
> > >> > include(${MyLib_USE_FILE}) which basically do a LINK_DIRECTORIES
> with
> > >>
> > >> the
> > >>
> > >> > absolute path of the library.
> > >> >
> > >> > Then I do add_executable and target_link_libraries(MyExample
> > >> > ${MyLib_LIBRARIES})
> > >> >
> > >> > Compilation is working fine. There is these options:
> > >> >
> > >> > -L/Absolute/Path/To/MyLib -lMyLib
> > >> >
> > >> > But at runtime, library cannot be found.
> > >> >
> > >> > Would it be possible to put the full path of my library when
> linking in
> > >>
> > >> the
> > >>
> > >> > CMakeLists ?
> > >>
> > >> You should use the full path to the library instead of
> LINK_DIRECTORIES.
> > >> Its easiest if you use install(EXPORT ...) to have CMake generate an
> > >> export
> > >> file for you that can be included by your FindMyLib.cmake file.
> > >> That export file will use the full path, and include any other
> necessary
> > >> information about the library.
> > >>
> > >> But to solve the problem of finding the library at runtime
> (specifying a
> > >> full
> > >> path won't solve it), CMake 2.8.12 has a new feature to address
> exactly
> > >> that
> > >> problem.  For details: http://www.kitware.com/blog/home/post/510
> > >>
> > >> If you can use CMake 2.8.12, then you need to put
> > >>
> > >>  set(MACOSX_RPATH 1)
> > >>
> > >> in the CMakeLists.txt of MyLib.
> > >>
> > >> If the user is using 2.8.12, then any executable they compile with
> your
> > >> library will be able to find the library, no matter where it is.
> > >>
> > >> By the way, 2.8.12 is in a release candidate stage right now, and
> right
> > >> now
> > >> would be a good time for you to test the new feature that is meant to
> > >> solve
> > >> your problem.
> > >>
> > >> Clint
> > >
> > > --
> > > Laurent Chauvin, MS
> > > Surgical Navigation and Robotics Laboratory, Radiology Department
> > > Brigham And Women's Hospital, Harvard Medical School
> > > http://wiki.ncigt.org/index.php/User:Lchauvin
> --
> Clinton Stimpson
> Elemental Technologies, Inc
> Computational Simulation Software, LLC
> www.csimsoft.com
>

-- 
Laurent Chauvin, MS
Surgical Navigation and Robotics Laboratory, Radiology Department
Brigham And Women's Hospital, Harvard Medical School
http://wiki.ncigt.org/index.php/User:Lchauvin
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