[CMake] OBJECT libraries and INTERFACE_SOURCES

[Giovanni Funchal]

Hello,

PRIVATE works, but I don't understand why (the only difference between the
two examples is using a subdirectory).

Using ${CMAKE_CURRENT_SOURCE_DIR} does not work.

Thanks,
-- Giovanni


On Fri, Dec 9, 2016 at 4:17 PM, Chuck Atkins <chuck.atkins at kitware.com>
wrote:

> Hi Giovanni,
> Does it work if you add lib1 as a private dependency of lib2?  i.e.:
> target_link_libraries(lib2 PRIVATE lib1)
>
> Also, it shouldn't matter but what about in your original example if you
> use the full path to the source file instead while still keeping the public
> link dependency?  i.e.:
> add_library(lib1-obj OBJECT $(CMAKE_CURRENT_SOURCE_DIR}/lib1.cpp).
>
> ----------
> Chuck Atkins
> Staff R&D Engineer, Scientific Computing
> Kitware, Inc.
>
>
> On Fri, Dec 9, 2016 at 5:26 AM, Giovanni Funchal <gio at cloudnc.co.uk>
> wrote:
>
>> Hi,
>>
>> Apologies, the problem wasn't properly minimised because I had some
>> trouble wrapping my head around it. Here's two complete examples which I
>> hope can explain the problem better this time.
>>
>> 1) This works:
>>
>> [CMakeLists.txt]
>>     cmake_minimum_required(VERSION 3.6)
>>     project(Test)
>>     add_library(lib1-obj OBJECT lib1.cpp)
>>     add_library(lib1 INTERFACE)
>>     set_target_properties(lib1 PROPERTIES INTERFACE_SOURCES
>> $<TARGET_OBJECTS:lib1-obj>)
>>     add_library(lib2 lib2.cpp)
>>     target_link_libraries(lib2 lib1)
>>     add_executable(main main.cpp)
>>     target_link_libraries(main lib2)
>>
>> 2) But this does not:
>>
>> [CMakeLists.txt]
>>     cmake_minimum_required(VERSION 3.6)
>>     project(Test)
>>     add_library(lib1-obj OBJECT lib1.cpp)
>>     add_library(lib1 INTERFACE)
>>     set_target_properties(lib1 PROPERTIES INTERFACE_SOURCES
>> $<TARGET_OBJECTS:lib1-obj>)
>>     add_library(lib2 lib2.cpp)
>>     target_link_libraries(lib2 lib1)
>>     add_subdirectory(main)
>>
>> [main/CMakeLists.txt]
>>     add_executable(main main.cpp)
>>     target_link_libraries(main lib2)
>>
>> With the second example, I get an error "cannot find source file
>> lib1.cpp.o tried extensions...".
>>
>> Thanks,
>> -- Giovanni
>>
>>
>> On Thu, Dec 8, 2016 at 9:56 PM, Stephen Kelly <steveire at gmail.com> wrote:
>>
>>> Giovanni Funchal wrote:
>>>
>>> > Hi,
>>> >
>>> > The help page [1] mentions that:
>>> >
>>> >> Although object libraries may not be named directly in calls to the
>>> >> target_link_libraries() command, they can be “linked” indirectly by
>>> >> using an Interface Library whose INTERFACE_SOURCES target property
>>> >> is set to name $<TARGET_OBJECTS:objlib>.
>>> >
>>> > However, I was unable to get this to work. Doing this:
>>> >
>>> > add_library(lib-obj OBJECT test.cpp)
>>> > add_library(lib INTERFACE)
>>> > add_dependencies(lib lib-obj)
>>> > set_target_properties(lib PROPERTIES INTERFACE_SOURCES
>>> > $<TARGET_OBJECTS:lib-obj>)
>>> >
>>> > And then trying to specify lib in link_libraries of an executable
>>> yields
>>> > an error message "Cannot find source file: ... Tried extensions:... ".
>>> >
>>> > Am I doing something wrong?
>>>
>>> This works for me:
>>>
>>>     cmake_minimum_required(VERSION 3.3)
>>>
>>>     project(testit CXX)
>>>
>>>     add_library(lib-obj OBJECT foo.cpp)
>>>     add_library(lib-iface INTERFACE)
>>>     set_target_properties(lib-iface PROPERTIES
>>>       INTERFACE_SOURCES $<TARGET_OBJECTS:lib-obj>
>>>     )
>>>     add_executable(main foo-user.cpp)
>>>     target_link_libraries(main lib-iface)
>>>
>>>
>>> Thanks,
>>>
>>> Steve.
>>>
>>>
>>> --
>>>
>>> Powered by www.kitware.com
>>>
>>> Please keep messages on-topic and check the CMake FAQ at:
>>> http://www.cmake.org/Wiki/CMake_FAQ
>>>
>>> Kitware offers various services to support the CMake community. For more
>>> information on each offering, please visit:
>>>
>>> CMake Support: http://cmake.org/cmake/help/support.html
>>> CMake Consulting: http://cmake.org/cmake/help/consulting.html
>>> CMake Training Courses: http://cmake.org/cmake/help/training.html
>>>
>>> Visit other Kitware open-source projects at
>>> http://www.kitware.com/opensource/opensource.html
>>>
>>> Follow this link to subscribe/unsubscribe:
>>> http://public.kitware.com/mailman/listinfo/cmake
>>
>>
>>
>> --
>>
>> Powered by www.kitware.com
>>
>> Please keep messages on-topic and check the CMake FAQ at:
>> http://www.cmake.org/Wiki/CMake_FAQ
>>
>> Kitware offers various services to support the CMake community. For more
>> information on each offering, please visit:
>>
>> CMake Support: http://cmake.org/cmake/help/support.html
>> CMake Consulting: http://cmake.org/cmake/help/consulting.html
>> CMake Training Courses: http://cmake.org/cmake/help/training.html
>>
>> Visit other Kitware open-source projects at
>> http://www.kitware.com/opensource/opensource.html
>>
>> Follow this link to subscribe/unsubscribe:
>> http://public.kitware.com/mailman/listinfo/cmake
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://public.kitware.com/pipermail/cmake/attachments/20161209/d304ce51/attachment.html>