Duplicate builds with target_sources

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Duplicate builds with target_sources

Wesley Smith
I have a library target defined as


add_library(mylib_core
    core_source1.cpp
    core_source2.cpp
    core_source3.cpp
)

if(UNIX)
    target_sources(mylib_core PUBLIC
        ${CMAKE_CURRENT_SOURCE_DIR}/core_source4.cpp
        ${CMAKE_CURRENT_SOURCE_DIR}/core_source5.cpp
    )
endif()


Then a target that uses it as a dependency:


add_library(mylib_thing
    thing_source1.cpp
    thing_source2.cpp
    thing_source3.cpp
)

target_link_libraries(mylib_thing
    PUBLIC
        mylib_core
)

When building with static libs, I noticed that the sources defined on mylib_core with target_sources are building twice.


[ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/thing_source1.cpp.o
[ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/thing_source2.cpp.o
[ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/thing_source3.cpp.o
[ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/__/mylib_core/core_source4.cpp.o
[ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/__/mylib_core/core_source5.cpp.o

The last two source files were already built when mylib_core was built.  Why are they being built again under mylib_thing?  When these files were defined in the add_library() call, this didn't happen.  Any thoughts?  Is it related to the PUBLIC v. PRIVATE enum?  If so, what is the setting on sources when defining them via add_library()?

thanks,
wes


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Re: Duplicate builds with target_sources

Robert Maynard
You have defined 4 && 5 as public sources so that means that consumers
of mylib_core and mylib_core will build them. If you want the sources
to be part of mylib_core the sources should be private, if you want
the sources to be part of mylib_thing use interface. In general don't
use PUBLIC with target_sources.
On Tue, Nov 20, 2018 at 9:19 AM Wesley Smith <[hidden email]> wrote:

>
> I have a library target defined as
>
>
> add_library(mylib_core
>     core_source1.cpp
>     core_source2.cpp
>     core_source3.cpp
> )
>
> if(UNIX)
>     target_sources(mylib_core PUBLIC
>         ${CMAKE_CURRENT_SOURCE_DIR}/core_source4.cpp
>         ${CMAKE_CURRENT_SOURCE_DIR}/core_source5.cpp
>     )
> endif()
>
>
> Then a target that uses it as a dependency:
>
>
> add_library(mylib_thing
>     thing_source1.cpp
>     thing_source2.cpp
>     thing_source3.cpp
> )
>
> target_link_libraries(mylib_thing
>     PUBLIC
>         mylib_core
> )
>
> When building with static libs, I noticed that the sources defined on mylib_core with target_sources are building twice.
>
>
> [ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/thing_source1.cpp.o
> [ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/thing_source2.cpp.o
> [ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/thing_source3.cpp.o
> [ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/__/mylib_core/core_source4.cpp.o
> [ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/__/mylib_core/core_source5.cpp.o
>
> The last two source files were already built when mylib_core was built.  Why are they being built again under mylib_thing?  When these files were defined in the add_library() call, this didn't happen.  Any thoughts?  Is it related to the PUBLIC v. PRIVATE enum?  If so, what is the setting on sources when defining them via add_library()?
>
> thanks,
> wes
>
> --
>
> 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:
>
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Re: Duplicate builds with target_sources

Wesley Smith
Thank you for the explanation Robert.

On Tue, Nov 20, 2018 at 7:34 AM Robert Maynard <[hidden email]> wrote:
You have defined 4 && 5 as public sources so that means that consumers
of mylib_core and mylib_core will build them. If you want the sources
to be part of mylib_core the sources should be private, if you want
the sources to be part of mylib_thing use interface. In general don't
use PUBLIC with target_sources.
On Tue, Nov 20, 2018 at 9:19 AM Wesley Smith <[hidden email]> wrote:
>
> I have a library target defined as
>
>
> add_library(mylib_core
>     core_source1.cpp
>     core_source2.cpp
>     core_source3.cpp
> )
>
> if(UNIX)
>     target_sources(mylib_core PUBLIC
>         ${CMAKE_CURRENT_SOURCE_DIR}/core_source4.cpp
>         ${CMAKE_CURRENT_SOURCE_DIR}/core_source5.cpp
>     )
> endif()
>
>
> Then a target that uses it as a dependency:
>
>
> add_library(mylib_thing
>     thing_source1.cpp
>     thing_source2.cpp
>     thing_source3.cpp
> )
>
> target_link_libraries(mylib_thing
>     PUBLIC
>         mylib_core
> )
>
> When building with static libs, I noticed that the sources defined on mylib_core with target_sources are building twice.
>
>
> [ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/thing_source1.cpp.o
> [ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/thing_source2.cpp.o
> [ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/thing_source3.cpp.o
> [ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/__/mylib_core/core_source4.cpp.o
> [ 60%] Building CXX object mylib_thing/CMakeFiles/mylib_thing.dir/__/mylib_core/core_source5.cpp.o
>
> The last two source files were already built when mylib_core was built.  Why are they being built again under mylib_thing?  When these files were defined in the add_library() call, this didn't happen.  Any thoughts?  Is it related to the PUBLIC v. PRIVATE enum?  If so, what is the setting on sources when defining them via add_library()?
>
> thanks,
> wes
>
> --
>
> 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

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