How to include header files in external library in CMake

Question

I have a C application which is running on Raspberry Pi 3 and currently, I have to build it on PI with Cmake. I am trying to build it on Ubuntu machine. I have added a CMAKE_TOOLCHAIN_FILE as described here . I could run cmake. -DCMAKE_TOOLCHAIN_FILE cmake. -DCMAKE_TOOLCHAIN_FILE without any problem but the "make" command is not successful and it can not find a header file inside one of the external library: "mirsdrapi-rsp". The error message is:

fatal error: mirsdrapi-rsp.h: No such file or directory
 #include "mirsdrapi-rsp.h"
                           ^
compilation terminated.

I have created a folder named "lib" and have put the "libmirsdrapi-rsp.so" file inside it. my CMakeLists.txt is as below:

cmake_minimum_required(VERSION 3.4.1)
set(CMAKE_C_STANDARD 11)
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_C_STANDARD_REQUIRED ON)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -pedantic -Wextra -v -g -D_XOPEN_SOURCE")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -pedantic -Wextra -v ")
set(CMAKE_EXE_LINKER_FLAGS  ${CMAKE_EXE_LINKER_FLAGS} "-v")
set (SDR_API_PATH ${CMAKE_SOURCE_DIR}/lib)
include_directories (include ${SDR_API_PATH})

include_directories("${CMAKE_SOURCE_DIR}/lib")

find_library(mirslocation NAMES mirsdrapi-rsp HINTS ${SDR_API_PATH} NO_CMAKE_FIND_ROOT_PATH)
message(STATUS ${mirslocation})

add_library(mirs STATIC IMPORTED)
set_target_properties(mirs PROPERTIES IMPORTED_LOCATION ${mirslocation})

target_link_libraries (raspberryPiDaemon mirs)
target_link_libraries(raspberryPiDaemon m)

Cmake is printing the right path of the library mirsdrapi-rsp while running "find_library" and as I mentioned I am getting the error message just while running "make" command and not "cmake" command. My content of CMAKE_TOOLCHAIN_FILE is as below:

# Define our host system
SET(CMAKE_SYSTEM_NAME Linux)
SET(CMAKE_SYSTEM_VERSION 1)

# Define the cross compiler locations
SET(CMAKE_C_COMPILER   ${CMAKE_SOURCE_DIR}/../tools-master/arm-bcm2708/arm-rpi-4.9.3-linux-gnueabihf/bin/arm-linux-gnueabihf-gcc)
SET(CMAKE_CXX_COMPILER ${CMAKE_SOURCE_DIR}/../tools-master/arm-bcm2708/arm-rpi-4.9.3-linux-gnueabihf/bin/arm-linux-gnueabihf-gcc)

# Define the sysroot path for the RaspberryPi distribution in our tools folder 
SET(CMAKE_FIND_ROOT_PATH ${CMAKE_SOURCE_DIR}/../tools-master/arm-bcm2708/arm-rpi-4.9.3-linux-gnueabihf/arm-linux-gnueabihf/sysroot/SET)


# Use our definitions for compiler tools
SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
# Search for libraries and headers in the target directories only
SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY BOTH)
SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE BOTH)

add_definitions(-Wall -std=c11)

Anybody knows how I can add the header file from mirsdrapi-rsp library to include path?

Answer 1

I guess that you're setting include_directories to the wrong path (it is set 2 times to ${CMAKE_SOURCE_DIR}/lib which must be the folder of libraries not the header files). Check again the correct location of the missing header file.

More precisely: you need to find the path of mirsdrapi-rsp.h and let CMake know it just like for find_library:

find_path(MIRSDRAPI_INCLUDE_DIRS NAMES mirsdrapi-rsp.h PATHS {proper-location})

if (MIRSDRAPI_INCLUDE_DIRS)
  target_include_directories(raspberryPiDaemon PRIVATE ${MIRSDRAPI_INCLUDE_DIRS})
endif()

In addition, you can set the INTERFACE_INCLUDE_DIRECTORIES property to the library like this:

set_property(TARGET mirsdrapi-rsp APPEND PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${MIRSDRAPI_INCLUDE_DIRS})

This way, target_include_directories might be unnecessary and target_link_directories should be enough.