[CMake] transitive linkage of OBJECT library targets

[Richard Szabo]

With Public it is still the same problem :(

cmake_minimum_required(VERSION 3.14)
project(test_object_lib_nesting)

set(CMAKE_CXX_STANDARD 14)

add_library(first_object_lib OBJECT first.cpp)

add_library(second_object_lib OBJECT second.cpp)

target_link_libraries(second_object_lib PUBLIC first_object_lib)

add_executable(test_object_lib_nesting main.cpp)

target_link_libraries(test_object_lib_nesting second_object_lib)


/cmake -E cmake_link_script
CMakeFiles/test_object_lib_nesting.dir/link.txt --verbose=1
/usr/bin/clang++-6.0  -g
CMakeFiles/test_object_lib_nesting.dir/main.cpp.o
CMakeFiles/second_object_lib.dir/second.cpp.o  -o
test_object_lib_nesting
CMakeFiles/second_object_lib.dir/second.cpp.o: In function
`Second::get_second()':
/home/csita/CLionProjects/test_object_lib_nesting/second.cpp:10:
undefined reference to `First::get_first() const'
clang: error: linker command failed with exit code 1 (use -v to see invocation)

I read the issue and it seems that there is no solution jet ....

Is there an easy / not so easy workaround ?
I have a dependency tree which can go down to 20 - 30 libs. (code
generator ) also diamond graph. :(.

Cheers
Richard

On Wed, 22 May 2019 at 14:25, Robert Maynard <robert.maynard at kitware.com> wrote:
>
> This is a known limitation of the current design. Only directly linked
> object library objects are propagated.
>
> For more details on why see: https://gitlab.kitware.com/cmake/cmake/issues/18090
>
> On Wed, May 22, 2019 at 1:48 AM Richard Szabo <sz.richard at gmail.com> wrote:
> >
> > Hi cmakers
> >
> > I'm trying to get the following example working:
> > ```
> > cmake_minimum_required(VERSION 3.14)
> > project(test_object_lib_nesting)
> >
> > set(CMAKE_CXX_STANDARD 14)
> >
> > add_library(first_object_lib OBJECT first.cpp)
> >
> > add_library(second_object_lib OBJECT second.cpp)
> >
> > target_link_libraries(second_object_lib first_object_lib)
> >
> > add_executable(test_object_lib_nesting main.cpp)
> >
> > target_link_libraries(test_object_lib_nesting second_object_lib)
> > ```
> >
> > The problem I have that the linker command line will have only the
> > second.cpp.o for linking the first.cpp.o will not be added as link
> > object to the exe. Causing missing symbols on exe linkage.
> >
> > How to transitively resolve and link "nested" Object library targets ?.
> > --
> >
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