bundle_static.cmake

# https://cristianadam.eu/20190501/bundling-together-static-libraries-with-cmake/
function(bundle_static_library tgt_name bundled_tgt_name library_name)
  list(APPEND static_libs ${tgt_name})
  set(dep_libs "")

  function(_recursively_collect_dependencies input_target)
    set(_input_link_libraries LINK_LIBRARIES)
    get_target_property(_input_type ${input_target} TYPE)
    if (${_input_type} STREQUAL "INTERFACE_LIBRARY")
      set(_input_link_libraries INTERFACE_LINK_LIBRARIES)
    endif()
    get_target_property(public_dependencies ${input_target} ${_input_link_libraries})
    foreach(dependency IN LISTS public_dependencies)
      if(TARGET ${dependency})
        get_target_property(alias ${dependency} ALIASED_TARGET)
        if (TARGET ${alias})
          set(dependency ${alias})
        endif()
        get_target_property(_type ${dependency} TYPE)
        if (${_type} STREQUAL "STATIC_LIBRARY")
          list(APPEND static_libs ${dependency})
        endif()

        get_property(library_already_added
          GLOBAL PROPERTY _${tgt_name}_static_bundle_${dependency})
        if (NOT library_already_added)
          set_property(GLOBAL PROPERTY _${tgt_name}_static_bundle_${dependency} ON)
          _recursively_collect_dependencies(${dependency})
        endif()
      elseif(dependency)
        list(APPEND dep_libs ${dependency})
      endif()
    endforeach()
    set(static_libs ${static_libs} PARENT_SCOPE)
    set(dep_libs ${dep_libs} PARENT_SCOPE)
  endfunction()

  _recursively_collect_dependencies(${tgt_name})

  list(REMOVE_DUPLICATES static_libs)
  list(REMOVE_DUPLICATES dep_libs)

  set(bundled_tgt_full_name 
    ${CMAKE_BINARY_DIR}/${CMAKE_STATIC_LIBRARY_PREFIX}${library_name}${CMAKE_STATIC_LIBRARY_SUFFIX})
  
  if (APPLE)
    find_program(lib_tool libtool REQUIRED)

    foreach(tgt IN LISTS static_libs)
      list(APPEND static_libs_full_names $<TARGET_FILE:${tgt}>)
    endforeach()

    add_custom_command(
      COMMAND ${lib_tool} -static -o ${bundled_tgt_full_name} ${static_libs_full_names}
      OUTPUT ${bundled_tgt_full_name}
      COMMENT "Bundling ${bundled_tgt_name}"
      VERBATIM)
  elseif(UNIX OR MINGW)
    file(WRITE ${CMAKE_BINARY_DIR}/${bundled_tgt_name}.ar.in
    "CREATE ${bundled_tgt_full_name}\n" )
        
    foreach(tgt IN LISTS static_libs)
    file(APPEND ${CMAKE_BINARY_DIR}/${bundled_tgt_name}.ar.in
        "ADDLIB $<TARGET_FILE:${tgt}>\n")
    endforeach()

    file(APPEND ${CMAKE_BINARY_DIR}/${bundled_tgt_name}.ar.in "SAVE\n")
    file(APPEND ${CMAKE_BINARY_DIR}/${bundled_tgt_name}.ar.in "END\n")

    file(GENERATE
         OUTPUT ${CMAKE_BINARY_DIR}/${bundled_tgt_name}.ar
         INPUT ${CMAKE_BINARY_DIR}/${bundled_tgt_name}.ar.in)

    set(ar_tool ${CMAKE_AR})
    if (CMAKE_INTERPROCEDURAL_OPTIMIZATION)
        set(ar_tool ${CMAKE_CXX_COMPILER_AR})
    endif()

    add_custom_command(
        COMMAND ${ar_tool} -M < ${CMAKE_BINARY_DIR}/${bundled_tgt_name}.ar
        OUTPUT ${bundled_tgt_full_name}
        COMMENT "Bundling ${bundled_tgt_name}"
        VERBATIM)
  elseif(WIN32)
    # https://stackoverflow.com/a/38096930/1806760
    get_filename_component(vs_bin_path "${CMAKE_LINKER}" DIRECTORY)

    find_program(lib_tool lib HINTS "${vs_bin_path}" REQUIRED)

    foreach(tgt IN LISTS static_libs)
      list(APPEND static_libs_full_names $<TARGET_FILE:${tgt}>)
    endforeach()

    add_custom_command(
      COMMAND ${lib_tool} /NOLOGO /OUT:${bundled_tgt_full_name} ${static_libs_full_names}
      OUTPUT ${bundled_tgt_full_name}
      COMMENT "Bundling ${bundled_tgt_name}"
      VERBATIM)
  else()
    message(FATAL_ERROR "Unknown bundle scenario!")
  endif()

  add_custom_target(bundling_target ALL DEPENDS ${bundled_tgt_full_name})
  add_dependencies(bundling_target ${tgt_name})

  add_library(${bundled_tgt_name} STATIC IMPORTED)
  set_target_properties(${bundled_tgt_name} 
    PROPERTIES 
      IMPORTED_LOCATION ${bundled_tgt_full_name}
      INTERFACE_INCLUDE_DIRECTORIES $<TARGET_PROPERTY:${tgt_name},INTERFACE_INCLUDE_DIRECTORIES>
      INTERFACE_LINK_LIBRARIES "${dep_libs}")
      #IMPORTED_LINK_INTERFACE_LIBRARIES "${dep_libs}") # Deprecated
  add_dependencies(${bundled_tgt_name} bundling_target)

endfunction()