On 05/20/2018 02:21 PM, Gößwein Matthias / eeas gmbh wrote: > I found a strange behavior within the object libraries in the upcoming > CMake 3.12 (I used 3.11.20180519-gdb88f for testing).
Thanks for trying it out! > If I have for example two object libraries, which are used in one > executable: > > add_library(ObjLib1 OBJECT ObjLib1.c) > target_include_directories(ObjLib1 PUBLIC ...) > > add_library(ObjLib2 OBJECT ObjLib2.c) > target_include_directories(ObjLib2 PUBLIC ...) > > add_executable(MyExe main.c) > target_link_libraries(MyExe ObjLib1 ObjLib2) > > Then this works fine. Good. > But if for some reason one object library "links" > to the other and this is used for the executable then it does not work: > > add_library(ObjLib1 OBJECT ObjLib1.c) > target_include_directories(ObjLib1 PUBLIC ...) > target_link_libraries(ObjLib1 PUBLIC ObjLib2) > > add_library(ObjLib2 OBJECT ObjLib2.c) > target_include_directories(ObjLib2 PUBLIC ...) > > add_executable(MyExe main.c) > target_link_libraries(MyExe ObjLib1) > > I only get the usage requirements of ObjLib2, but not the object files > of ObjLib2 into the executable. This is expected as things are currently designed. Object files are only linked when the object library is *directly* referenced by a target. Only usage requirements are transitive, not the object files. > If I use STATIC Libraries instead it works. > I read the documentation too and i know that > there is no link step for object libraries, but I guess it's the same > for the static libraries Static libraries have an archiving step rather than a link step and plays the role of collecting object files together. Object libraries have no such step. A major distinction is that listing object files on a link line causes them to be included in the link unconditionally. We can't simply list all object library transitive dependencies or their objects may be included multiple times in one target or duplicated in multiple dependent targets. > usage of object libraries which depend on other object libraries > is not working well...I have to repeat in some sort the dependency Yes, and this is because object libraries are meant to be building blocks for normal libraries and executables. How they are packaged into those libraries and executables needs to be in full control of project code. For example, maybe your ObjLib2 objects are supposed to go into some static library that MyExe links. -Brad -- 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: https://cmake.org/mailman/listinfo/cmake-developers
