[CMake] Dynamic library RPATH on OSX

[Steve Skutnik]

After some more attempts, I discovered the issue which was somewhat unclear
to me before.

CMake has the option CMAKE_INSTALL_NAME_DIR which specifies the parameter
for the install_name_tool in OSX. I was attempting to use this with "Module
B", however it turns out this is incorrect. Instead, the user should use
this command on "Module A" such that when "Module B" links to "Module A",
it pulls up the full path to find "Module A".

Adding this to the "Module A" CMakeLists.txt and rebuilding correctly
propagated the path to "Module A" when building "Module B" - my executable
now finds the dynamic library correctly.

Hopefully this helps someone else in the future...

-Steve
---
Steve Skutnik, Ph.D.
http://neutroneconomy.blogspot.com


On Wed, Feb 13, 2013 at 11:58 AM, Steve Skutnik <skutnik at gmail.com> wrote:

> I'm having an issue with the RPATH not showing up for one of my shared
> libraries on OSX. Basically, I end up with a "bare" rpath to one of my
> shared libraries (i.e., no path prefix) when I check my binary using otool
> - L
>
> Specifically, I have a project with a structure that looks like this
>
> project/module_A
> project/module_B
>
> I'm trying to build "Module B", which depends on a shared library I build
> in "Module A". (I also use several other shared libraries, but all of them
> are in system paths, i.e., /usr/local and /usr/lib.). What ends up
> happening is that all of the rpaths are set *except* for my shared library
> from Module A (for both the build and install versions of the binary).
>
> After carefully reading the CMake primer on RPath handling here:
>
> http://www.cmake.org/Wiki/CMake_RPATH_handling
>
> I tried the suggestion under "Always full rpath", i.e., my CMakeLists.txt
> file has the following:
>
> # use, i.e. don't skip the full RPATH for the build tree
> SET(CMAKE_SKIP_BUILD_RPATH  FALSE)
>
> # when building, don't use the install RPATH already
> # (but later on when installing)
> SET(CMAKE_BUILD_WITH_INSTALL_RPATH FALSE)
>
> SET(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")
>
> # add the automatically determined parts of the RPATH
> # which point to directories outside the build tree to the install RPATH
> SET(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
>
>
> # the RPATH to be used when installing, but only if it's not a system directory
> LIST(FIND CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES "${CMAKE_INSTALL_PREFIX}/lib" isSystemDir)
> IF("${isSystemDir}" STREQUAL "-1")
>    SET(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")
> ENDIF("${isSystemDir}" STREQUAL "-1")
>
>
> However, this still doesn't appear to be setting the RPATH variable for my
> dynamic library.  I likewise checked that CMAKE_INSTALL_RPATH is set
> correctly (i.e., the library from Module A sits in that directory).
> However, nothing I do seems to prefix an RPATH directory to my shared
> library for Module A.
>
> One other thing - I've also tried building this code on Linux
> (Ubuntu-12.10), and I've noticed that the same configuration correctly sets
> the RPATH for Module A - so this seems to be specific to OSX.
>
> What am I missing here? Going through the list archives, I've seen this
> problem pop up a few times with respect to OSX, but I haven't really seen
> anything that specifically solves this issue. Specifically, this message
> from a few weeks ago seems to be running into the exact same issue, but I
> don't see any replies:
>
> http://www.cmake.org/pipermail/cmake/2013-January/053335.html
>
> The only other thread I've seen on this recently is here:
>
> http://www.cmake.org/pipermail/cmake/2011-April/043888.html
>
> The solution here was pretty much to either use install_name_tool manually
> (which does work, but it requires one to do it each time you build) or to
> use BundleUtilities. However, I noticed that CMake runs install_name_tool
> on its own for a library which is built with Module B (i.e., I have
> libModuleB_core.dylib which is built and linked into the moduleB binary);
> i.e., this shows up in cmake_install.cmake. So shouldn't there be some way
> to get CMake to appropriately run install_name_tool for me for Module A as
> well? Or at the very least, is there a reason no RPATH is being appended to
> Module A?
>
> Thanks.
>
> -Steve
> ---
> Steve Skutnik, Ph.D.
> http://neutroneconomy.blogspot.com
>
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