In my project, I have an external dependency (a Github repository) from which I want to copy certain files to the source and include directories of my project. I only need a subset of the source and header files in the external repository, so I just want to be able to copy the updated versions of the files I need into the relevant directories in my project. I believe ExternalProject_Add should be the right command to download the files from an external project but I can't figure out how to copy them to my source and include directories before each build. Is there an option of ExternalProject_Add to achieve this, or should a custom build rule be added using add_custom_command which copies the files after the external project is downloaded?
ou can check the CMakeLists.txt of the external repository I want to link to here. I need to compile and install the library and don't want to compile the executables
You can add the external code either via git submodule if your code is inside a submodule, or by using FetchContent as expalined in the documentation:
include(FetchContent)
FetchContent_Declare(
screamrepo
GIT_REPOSITORY "https://github.com/EricssonResearch/scream"
)
FetchContent_GetProperties(screamrepo)
if(NOT screamrepo_POPULATED)
FetchContent_Populate(screamrepo)
endif()
# use ${screamrepo_SOURCE_DIR} for source dir
If the external code is well structured and exposes the library you want to have, then:
add_subdirectory(the/source/path EXCLUDE_FROM_ALL)
and use the library. If not, like in cases you do not like third party cmake configuration or it comes with unsupported configuration, write your own target add_library and configuration and include paths that use the other repository files from source dir.