[CMake] Absolute Path linking library

Clinton Stimpson clinton at elemtech.com
Wed Sep 4 15:05:34 EDT 2013 

On Wednesday, September 04, 2013 03:01:06 PM Laurent Chauvin wrote:
> Thank you for your help Clint.
> 
> I identified the problem. When I compile my library with
> CMAKE_MACOSX_RPATH, the library created is linked with
> @rpath/libMyLib.dylib.
> When I was recompiling (make) it was updating the library in the build
> directory but it was not re-installing (copying in the MyLibrary-install
> directory).
> That's why the link was keep failing.
> 
> Is there a way to automatically reinstall when recompiling in Cmake ?

Not really.
You can always do a "make install" instead of "make", which will do both the 
make and install in one step.

Clint

> 
> Thank you very much.
> -Laurent
> 
> On Wed, Sep 4, 2013 at 2:16 PM, Clinton Stimpson 
<clinton at elemtech.com>wrote:
> > On Wednesday, September 04, 2013 01:22:11 PM Laurent Chauvin wrote:
> > > Does your example still works if you replace this line:
> > > 
> > > target_link_libraries(app ${CMAKE_CURRENT_LIST_DIR}/../lib/liblib.dylib)
> > > 
> > > by this one:
> > > 
> > > target_link_libraries(app lib)
> > 
> > No.  It doesn't work.  I get "ld: library not found for -llib"
> > 
> > If I add a link_directories() I can get it working again.
> > If I were to use an export file, it would also work again.
> > 
> > Feel free to try experiment with the example I gave you to verify that the
> > library can be found at runtime without setting DYLD_LIBRARY_PATH.  You
> > only
> > need to supply 2 .cpp files with some dummy functions.  The library and
> > executable are in two separate directories.
> > 
> > Clint
> > 
> > > ?
> > > 
> > > Thank you.
> > > -Laurent
> > > 
> > > On Wed, Sep 4, 2013 at 1:18 PM, Clinton Stimpson
> > 
> > <clinton at elemtech.com>wrote:
> > > > On Wednesday, September 04, 2013 12:48:41 PM Laurent Chauvin wrote:
> > > > > Yes I'm using 2.8.12-rc2 for the library and the example.
> > > > > 
> > > > > But my example is not in the same directory as my library.
> > > > 
> > > > Neither was my example.
> > > > 
> > > > > I can see in your example you specify the full path in
> > > > > target_link_libraries of your library, which I could probably do.
> > > > > 
> > > > > The problem is, if later on my library I want to put the .dyld not
> > > > > in
> > > > > MyLib/lib but MyLib/testLib, then I will have (or users) to modify
> > 
> > all
> > 
> > > > > their CMakeLists to modify path of the library.
> > > > > That's why I would like not to have to hardcode the library path
> > 
> > into my
> > 
> > > > > example.
> > > > 
> > > > Of course the users shouldn't hard code it.  My example was simply
> > > > demonstrating the solution to the problem of locating the shared
> > 
> > library
> > 
> > > > at
> > > > runtime, which works in 2.8.12-rc2, without setting DYLD_LIBRARY_PATH.
> > > > 
> > > > Really, this problem/solution for finding the .dylib at runtime has
> > > > nothing to
> > > > do with whether your target_link_libraries() has a full path or not.
> >  
> >  Or
> >  
> > > > whether you are using LINK_DIRECTORIES or not.
> > > > I just tested with full path vs. LINK_DIRECTORIES, and it makes no
> > > > difference
> > > > to whether the library can be found at runtime.
> > > > 
> > > > As an aside, I'm encouraging you to not use LINK_DIRECTORIES.
> > > > 
> > > > Clint
> > > > 
> > > > > I'm using find_package to find my library, and include the use file,
> > > > 
> > > > which
> > > > 
> > > > > define the include_directories and link_directories.
> > > > > 
> > > > > I also checked the INSTALL(EXPORT ..), here
> > 
> > http://www.cmake.org/Wiki/CMake/Tutorials/How_to_create_a_ProjectConfig.cm
> > 
> > > > ak>
> > > > 
> > > > > e_file but I don't understand what it's doing and how it works.
> > > > > 
> > > > > Thank you.
> > > > > -Laurent
> > > > > 
> > > > > On Wed, Sep 4, 2013 at 12:26 PM, Clinton Stimpson
> > > > 
> > > > <clinton at elemtech.com>wrote:
> > > > > > On Wednesday, September 04, 2013 12:02:55 PM Laurent Chauvin 
wrote:
> > > > > > > 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 ?
> > > > > > 
> > > > > > You can leave your LINK_DIRECTORIES as its not the cause of your
> > > > 
> > > > runtime
> > > > 
> > > > > > failure to find the library.
> > > > > > 
> > > > > > For compiling MyExample, did you also use CMake 2.8.12 RC?
> > > > > > 
> > > > > > Here's a minimal example that works for me.
> > > > > > 
> > > > > > -- lib/CMakeLists.txt
> > > > > > set(CMAKE_MACOSX_RPATH 1)
> > > > > > add_library(lib SHARED lib.cpp)
> > > > > > 
> > > > > > -- app/CMakeLists.txt
> > > > > > add_executable(app app.cpp)
> > > > > > target_link_libraries(app
> > > > 
> > > > ${CMAKE_CURRENT_LIST_DIR}/../lib/liblib.dylib)
> > > > 
> > > > > > In lib/
> > > > > > I run "cmake . && make"
> > > > > > 
> > > > > > In app/
> > > > > > I run "cmake . && make && ./app"
> > > > > > 
> > > > > > With 2.8.12, it works.
> > > > > > 
> > > > > > With an older version, I get
> > > > > > dyld: Library not loaded: @rpath/liblib.dylib
> > > > > > 
> > > > > >   Referenced from: ..../app
> > > > > >   Reason: image not found
> > > > > > 
> > > > > > Trace/BPT trap
> > > > > > 
> > > > > > Clint
> > > > > > 
> > > > > > > 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
> > 
> > --
> > Clinton Stimpson
> > Elemental Technologies, Inc
> > Computational Simulation Software, LLC
> > www.csimsoft.com
-- 
Clinton Stimpson
Elemental Technologies, Inc
Computational Simulation Software, LLC
www.csimsoft.com

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