[CMake] How to get a list of all the static libraries that a target will link against ?

[Angeliki Chrysochou]

Hi Glenn,

Adding linker flags exactly in target_link_libraries is not a very good
practice in my opinion. To add specific linker flags to an executable, you
can use the variable CMAKE_EXE_LINKER_FLAGS, which you can edit before
calling add_executable. You could set this variable accordingly in your
static and dynamic CMakeLists.txt to include the flags you wish in the
following way:

set(CMAKE_EXE_LINKER_FLAGS "-whole-archive")

If you set this variable to include more custom linker flags which you want
to preserve across libraries, then you should set it in the following way
to preserve its old value:

set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -whole-archive")

If you want to edit linker flags for a shared library or a module target
you can use these cmake variables (set them before add_library):

CMAKE_SHARED_LINKER_FLAGS
CMAKE_MODULE_LINKER_FLAGS

Be aware that variables have CMakeLists.txt file scope, so if you set
different values in one CMakeLists.txt then they might get overwritten or
appended (depending on the way you edit the variable).

All the best,
Angeliki





On Sat, Jul 19, 2014 at 2:39 PM, Glenn Coombs <glenn.coombs at gmail.com>
wrote:

> Don't all shout at once :-)  I'm guessing there are no easy solutions
> then...
>
> --
> Glenn
>
>
> On 28 June 2014 14:33, Glenn Coombs <glenn.coombs at gmail.com> wrote:
>
>> I have a project which compiles and links into both a stand alone
>> executable and a dynamic shared library.  The library and the executable
>> link against the same project libraries but have different object files
>> containing their entry points: main.o for the executable and dll_main.o for
>> the library.  My project heirarchy looks like this (simplified a bit for
>> brevity):
>>
>> CMakeLists.txt
>>     mtx_source/CMakeLists.txt
>>     mtx_wrapper/CMakeLists.txt
>>     testbench/CMakeLists.txt
>>
>> The top level CMakeLists.txt calls add_subdirectory on the various
>> project specific library folders which each build a static library.  The
>> testbench folder is the one that builds both the executable and the dynamic
>> library.  When building the dynamic library I need to use the linker
>> options -whole-archive and -no-whole-archive to force my static project
>> libraries to be included into the dynamic library. The problem is how to
>> insert the -whole-archive and -no-whole-archive options so that they select
>> the correct set of libraries.  Currently in the testbench CMakeLists.txt
>> file I have these lines:
>>
>> set(libs
>>     VLC
>>     mvea
>>     ${SYSTEMC_SUPPORT_LIBRARIES}
>>     ${DEVIFSLAVE_LIBRARIES}
>>     ${SYSTEMC_LIBRARIES}
>>     ${SIM_UTILS_LIBRARIES}
>>     ${HWDEBUG_LIBRARIES}
>> )
>>
>> if (NOT STUB_OUT_MTX)
>>     list(APPEND libs mtx_wrapper)
>> endif()
>>
>> set(libs_dll ${libs} transif_slave)
>>
>> if (UNIX)
>>     list(INSERT libs_dll 0 -Wl,-whole-archive)
>>     list(APPEND libs_dll   -Wl,-no-whole-archive)
>> endif()
>>
>> add_library ( csim_dll SHARED ${sources_dll} ${headers_dll} )
>> add_executable( testbench       ${sources}     ${headers}     )
>>
>> target_link_libraries(csim_dll  ${libs_dll} ${PTHREADS_LIBRARIES} )
>> target_link_libraries(testbench ${libs}     ${PTHREADS_LIBRARIES} )
>>
>> which produces the following link line:
>>
>> /usr/bin/g++-4.7  -fPIC -m32  -m32 -m32 -fPIC -m32 -O3  -O3 -DHIDEBUG
>> -Wl,-Bsymbolic
>> -shared -Wl,-soname,libtopazhp.so
>> -o libtopazhp.so
>> CMakeFiles/csim_dll.dir/dll_main.cpp.o
>> CMakeFiles/csim_dll.dir/main_common.cpp.o
>> -lm -lrt -lm -lrt
>> -Wl,-whole-archive
>> ../mvea/VLC/libVLC.a
>> ../mvea/libmvea.a
>> ../systemCSupport/libsystemc_support.a
>> ../devif_slave/libDevifSlave.a
>> ../systemC/libsystemc.a
>> ../sim_utils/libsim_utils.a
>> ../hwdebug/libhwDebug.a
>> ../mtx_wrapper/libmtx_wrapper.a
>> ../transif/libtransif_slave.a
>> -Wl,-no-whole-archive
>> -lpthread -lz
>> ../systemC/libpthreads_dummy.a
>> ../external_mtx/src/external_mtx-build/metag/libmetag.a
>> ../external_mtx/src/external_mtx-build/metagcopro/libmetagcopro.a
>> ../external_mtx/src/external_mtx-build/metac/vmetastub/libvmetastub.a
>> ../external_mtx/src/external_mtx-build/metac/insim/libinsimfpu.a
>> ../external_mtx/src/external_mtx-build/mtx/insim-mtxg/libinsim-mtxg.a
>> ../external_mtx/src/external_mtx-build/mtx/libmtxc.a
>> -ldl -lm -lrt -lm -lrt
>>
>> The problem is that the 6 external_mtx libraries should have been
>> included inside the -whole-archive section.  These libraries are specified
>> in the mtx_wrapper folder with a target_link_libraries(mtx_wrapper
>> ${METASIM_LIBRARIES}) command.  I have managed to wrap the direct library
>> dependencies inside the -whole-archive but I need to ensure that any
>> sub-dependencies are included as well (and any dependencies they might have
>> recursively).  Any system dynamic libaries (-ldl -lm -lrt etc.) must appear
>> after the -no-whole-archive option otherwise the link fails.  The
>> mtx_wrapper library can be built in two ways and only one of them will add
>> the extra METASIM libraries as a dependency, the other way fakes that code
>> internally.  Adding the METASIM libraries via target_link_libraries()
>> inside the mtx_wrapper CMakeLists.txt correctly handles that dependency
>> when linking the standalone executable but is not working for linking the
>> dynamic library.
>>
>> Is there an easy way to get cmake to handle all this ?  Is there a way to
>> get a list of all the static libraries (libXXX.a) that will be included on
>> the link line for a target ?
>>
>> --
>> Glenn
>>
>>
>
> --
>
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