custom target as a target library in cmake

问题:

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.

回答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.