How does find_package(Boost) work with static and shared libraries? - c++

Question

I am currently working on a project that has multiple libraries and multiple executables. Some of the executables will link some of the libraries statically and others will be linked dynamically. My question is how to go about having the option to link a library statically or dynamically using find_package. I noticed boost has the option to set Boost_USE_STATIC_LIBS before calling find_package but I am not quite sure how Boost goes about using this. Does boost build both shared/static and then Boost_USE_STATIC_LIBS just picks the target? Would I strictly need to use MODULE mode or can I use CONFIG mode and what would be the benefit/costs of using either mode for this kind of behaviour?
My current approach uses config mode as all a library needs to do is just call rn_lib(<target_name>) and everything is set up for them. I am guessing the logic to pick the static vs shared target is done in the config/find file for the library.
Desired Behaviour
set(<lib_name>_USE_STATIC_LIBS TRUE)
find_package(<lib_name> REQUIRED)
Current CMakeLists.txt for libraries
function(rn_lib)
cmake_parse_arguments(RN_LIB
""
"NAME"
"SRCS;HEADERS"
${ARGN}
)
if (RN_LIB_NAME)
set(target_name ${RN_LIB_NAME})
else()
set(target_name ${PROJECT_NAME})
endif()
set(static_target_option ${target_name}_STATIC)
option(${static_target_option} "Force build as static library" OFF)
set(_config_file ${target_name}_config.h)
configure_file("cmake/${_config_file}.in" ${CMAKE_CURRENT_BINARY_DIR}/${_config_file})
if (${PROJECT_VERSION})
set(project_version ${PROJECT_VERSION})
else()
set(project_version 1.0)
endif()
if (static_target_option)
message("Build Static ${target_name}")
add_library(${target_name} STATIC
${RN_LIB_SRCS}
${RN_LIB_HEADERS}
)
else()
message("Build Shared ${target_name}")
# This could still produce a static library
add_library(${target_name}
${RN_LIB_SRCS}
${RN_LIB_HEADERS}
)
endif()
# setup lib variables
set(include_install_dir include)
set(include_install_abs ${RN_INSTALL_PATH}/${include_install_dir})
set(config_install_dir lib/cmake/${target_name})
set(generated_dir ${CMAKE_CURRENT_BINARY_DIR}/generated)
set(version_config ${generated_dir}/${target_name}ConfigVersion.cmake)
set(project_config ${generated_dir}/${target_name}Config.cmake)
set(package_namespace RustyNail::)
set(target_export_name ${target_name}Targets)
install(
FILES ${RN_LIB_HEADERS}
DESTINATION ${include_install_dir}/${base_name}
)
target_include_directories(
${target_name}
PUBLIC
$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
$<INSTALL_INTERFACE:${include_install_dir}>
)
write_basic_package_version_file(
${version_config}
VERSION ${project_version}
COMPATIBILITY AnyNewerVersion
)
configure_package_config_file(
${RN_CMAKE_PATH}/Config.cmake.in
${project_config}
INSTALL_DESTINATION ${config_install_dir}
)
install(
TARGETS ${target_name}
EXPORT ${target_export_name}
LIBRARY DESTINATION lib
ARCHIVE DESTINATION lib
RUNTIME DESTINATION bin
INCLUDES DESTINATION ${include_install_dir}
)
install(
FILES ${project_config} ${version_config}
DESTINATION ${config_install_dir}
)
install(
EXPORT ${target_export_name}
NAMESPACE ${package_namespace}
DESTINATION ${config_install_dir}
)
endfunction()
Project Tree
- < root>
- output dir
- lib
- bin
- build
- src
- lib
- lib1
- lib2
- apps
- app1
- app2