custom target as a target library in cmake

Question

I have a custom target that is in fact an externally generated library that I want to integrate in my build.

add_custom_command(        OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/liblib2.a        COMMAND make -f ${CMAKE_CURRENT_SOURCE_DIR}/makefile liblib2.a)  add_custom_target(lib2          DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/liblib2.a) 

How can I tell cmake that this target is in fact a library, where it can be found and where are the headers ?

To be clear : I don't want the upper CMakeList using this library having to manually specify include folders and the library location folder It must be done automatically (from the target properties).

On a standard cmake library I would just have to add the INTERFACE_INCLUDE_DIRECTORIES property in the library CMakeLists to make cmake link my app with the relevant -I and -L gcc parameters :

set_target_properties(lib1   PROPERTIES   INTERFACE_INCLUDE_DIRECTORIES   ${CMAKE_CURRENT_SOURCE_DIR}) 

But in the case of a custom target I don't know how to to it.

Any clue ?

Thanks for your help.

---

Thanks to zaufi it works!

For others who may be interested in embedded externally build target inside cmake here is what I did :

cmake_minimum_required(VERSION 2.8)  SET(LIB_FILE ${CMAKE_CURRENT_SOURCE_DIR}/bin/liblib2.a) SET(LIB_HEADER_FOLDER ${CMAKE_CURRENT_SOURCE_DIR}/include)  # how to build the result of the library add_custom_command(OUTPUT  ${LIB_FILE}                    COMMAND make                     WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})  # create a target out of the library compilation result add_custom_target(lib2_target DEPENDS ${LIB_FILE})  # create an library target out of the library compilation result add_library(lib2 STATIC IMPORTED GLOBAL) add_dependencies(lib2 lib2_target)  # specify where the library is and where to find the headers set_target_properties(lib2     PROPERTIES     IMPORTED_LOCATION ${LIB_FILE}     INTERFACE_INCLUDE_DIRECTORIES ${LIB_HEADER_FOLDER}) 

Now in a CMakeLists.txt I can do somthing like

add_subdirectory(${ROOT_DIR}/lib1 bin/lib1) add_subdirectory(${ROOT_DIR}/lib2 bin/lib2) add_executable(app app.c ) target_link_libraries(app lib1 lib2) 

No need to specify where the .a and the .h are.

Answer 1

You can use add_library() and tell that it actually imported. Then, using set_target_properties() you can set required INTERFACE_XXX properties for it. After that, you can use it as an ordinal target like every other built by your project.

Answer 2

Thank you for posting the solution. I have wrapped your snippet in a function:

function(add_external_library)     set(options)     set(oneValueArgs TARGET WORKING_DIRECTORY OUTPUT COMMENT)     set(multiValueArgs COMMAND INCLUDE_DIRS)     cmake_parse_arguments(ARGS "${options}" "${oneValueArgs}" ${multiValueArgs}" ${ARGN})      # Specify how to build the result of the library     add_custom_command(OUTPUT "${ARGS_OUTPUT}"         COMMAND ${ARGS_COMMAND}         WORKING_DIRECTORY "${ARGS_WORKING_DIRECTORY}"         COMMENT "${ARGS_COMMENT}")      # Create a target out of the library compilation result     add_custom_target(${ARGS_TARGET}_target DEPENDS ${ARGS_OUTPUT})      # Create an library target out of the library compilation result     add_library(${ARGS_TARGET} STATIC IMPORTED GLOBAL)     add_dependencies(${ARGS_TARGET} ${ARGS_TARGET}_target)      # Specify where the library is and where to find the headers     set_target_properties(${ARGS_TARGET}         PROPERTIES         IMPORTED_LOCATION "${ARGS_OUTPUT}"         INTERFACE_INCLUDE_DIRECTORIES "${ARGS_INCLUDE_DIRS}") endfunction()  # Example add_external_library(TARGET YourLib     COMMAND           /bin/bash compile_your_lib.sh     WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"     OUTPUT            "output/yourlib.a"     INCLUDE_DIRS      "include/a" "include/b"     COMMENT           "Building YourLib")  add_executable(YourExe) target_link_libraries(YourExe YourLib)