[CMake] Creating relocatable packages

Mon Oct 19 17:56:53 EDT 2015

I had a look at his example, but stopped at the 'export' line.  That's
just black magic to me :-)
CMake user package registry?  Yikes.

I stopped trying to use cmake for uberbuilds several years ago.
- Dan

On Mon, Oct 19, 2015 at 2:35 PM, Pau Garcia i Quiles
<pgquiles at elpauer.org> wrote:
> Hi Dan,
>
> On a second read, it seems Zac's problem was actually finding the dependency
> (libpcap) of a dependency. Or rather, making if findable, because the second
> depenency contains an absolute path which is broken due to
> cross-compilation.
>
> I have never used it but this page contains information on how to fix the
> paths in the config file to be relative instead of absolute. That should fix
> the problem:
>
> https://cmake.org/Wiki/CMake/Tutorials/How_to_create_a_ProjectConfig.cmake_file
>
>
>
> On Mon, Oct 19, 2015 at 11:15 PM, Dan Kegel <dank at kegel.com> wrote:
>>
>> Well, that's one answer.  But if you want to use system libpcap, it's not
>> a very satisfying one.
>>
>> It's odd that pcap doesn't ship with a .pc file.
>> I guess the pcap folks are hostile to pkgconfig because it's LGPL; see
>> https://github.com/the-tcpdump-group/libpcap/issues/374
>> - Dan
>>
>>
>>
>> On Mon, Oct 19, 2015 at 2:04 PM, Pau Garcia i Quiles
>> <pgquiles at elpauer.org> wrote:
>>>
>>> Hello,
>>>
>>> Use ExternalProject to build libpcap as part of your project. Make sure
>>> you use $ORIGIN in rpath everywhere. Install your application (and your
>>> bundled libpcap) to /opt to avoid polluting the system.
>>>
>>> On Mon, Oct 19, 2015 at 10:37 PM, Zac Bergquist <zbergquist99 at gmail.com>
>>> wrote:
>>>>
>>>> Thank you for your reply, Guillaume.
>>>>
>>>> I understand that this is the expected behavior.  I even linked to the
>>>> documentation that says this is the expected behavior.  What I don't
>>>> understand is how to resolve it.  Are you saying it is not possible to
>>>> create a relocatable package unless all dependencies are also using CMake?
>>>> That doesn't seem right.
>>>>
>>>> Should I be trying to write a package config file for libpcap, or is
>>>> there a better way to approach this?
>>>>
>>>> On Sat, Oct 17, 2015 at 8:19 AM, Guillaume Dumont
>>>> <dumont.guillaume at gmail.com> wrote:
>>>>>
>>>>> What you are seeing is the expected behavior. You can get a relocatable
>>>>> package if all your dependencies (in your case libcap) have themselves
>>>>> relocatable package config files with exported targets. Then you package
>>>>> should make use of find_dependency macro.
>>>>>
>>>>> On Fri, Oct 16, 2015 at 4:56 PM, Zac Bergquist <zbergquist99 at gmail.com>
>>>>> wrote:
>>>>>>
>>>>>> I've created a sample project to replicate my issue in hopes that it
>>>>>> would make it easier to troubleshoot.
>>>>>>
>>>>>> Thanks for any help,
>>>>>> Zac
>>>>>>
>>>>>> https://github.com/zmb3/cmaketest
>>>>>>
>>>>>> On Mon, Oct 12, 2015 at 8:53 AM, Zac Bergquist
>>>>>> <zbergquist99 at gmail.com> wrote:
>>>>>>>
>>>>>>> Hello,
>>>>>>>
>>>>>>> I'm trying to fix a project so that its output is relocatable.  The
>>>>>>> project is a library that itself depends on libpcap.  My goal is to be able
>>>>>>> to import the library into my CMake application and have CMake automatically
>>>>>>> link libpcap with it.
>>>>>>>
>>>>>>> I'm using a toolchain file that invokes an ARM cross compiler, sets
>>>>>>> CMAKE_INSTALL_PREFIX and appends it to CMAKE_FIND_ROOT_PATH.  This all seems
>>>>>>> to work well.
>>>>>>>
>>>>>>> What I'm seeing is that the exported files that get installed to
>>>>>>> CMAKE_INSTALL_PREFIX contain absolute paths to libpcap on my machine, which
>>>>>>> make them useless to other team members.
>>>>>>>
>>>>>>> The first thing I changed was to use CONFIGURE_PACKAGE_CONFIG_FILE
>>>>>>> instead of CONFIGURE_FILE.  This got rid of absolute paths in the generated
>>>>>>> CMake config file.
>>>>>>>
>>>>>>> However, I still have absolute paths in the CMake target import file
>>>>>>> that gets generated.  The IMPORTED_LINK_INTERFACE_LIBRARIES target property
>>>>>>> has an absolute path instead of one relative to CMAKE_INSTALL_PREFIX.
>>>>>>>
>>>>>>> I've read the "Creating Relocatable Packages" [1] section of the
>>>>>>> CMake packages documentation. I'm pretty sure this is what I'm running into,
>>>>>>> but I don't quite understand how to solve it.  The documentation says that I
>>>>>>> should be using imported targets, but I'm not sure how to do so.  The
>>>>>>> library is just using its own FindPCAP.cmake file to locate libpcap.
>>>>>>>
>>>>>>> Does anyone know of an example of a CMake package that imports other
>>>>>>> libraries?  I could also try to create a minimal example project with this
>>>>>>> setup if it would be helpful.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Zac
>>>>>>>
>>>>>>> [1]:
>>>>>>> https://cmake.org/cmake/help/v3.3/manual/cmake-packages.7.html#creating-relocatable-packages
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>>
>>>>>> Powered by www.kitware.com
>>>>>>
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>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Guillaume Dumont
>>>>> =========================
>>>>> dumont.guillaume at gmail.com
>>>>
>>>>
>>>>
>>>> --
>>>>
>>>> Powered by www.kitware.com
>>>>
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>>>
>>>
>>>
>>>
>>> --
>>> Pau Garcia i Quiles
>>> http://www.elpauer.org
>>> (Due to my workload, I may need 10 days to answer)
>>>
>>> --
>>>
>>> Powered by www.kitware.com
>>>
>>> Please keep messages on-topic and check the CMake FAQ at:
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>>
>>
>
>
>
> --
> Pau Garcia i Quiles
> http://www.elpauer.org
> (Due to my workload, I may need 10 days to answer)