Link external library CMakeLists.txt on Windows - c++

Question

I'm trying to realize a CMakeLists.txt to compile my project under Linux and Windows. I use two libraries : SFML and boost. However, I want that my project can be built under Linux or Windows without the installation of libraries from a user.
I explain. Libraries SFML and boost are compiled and placed in my folder project and I want that no matter on which computer I download my project, I can build it.
And here is my problem, I can't link externally from the libraries folder in my folder project, the SFML and boost libraries.
Here is my CMakeLists.txt :
cmake_minimum_required(VERSION 3.0)
project(r-type_client CXX)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")
include_directories(./boost/include
./SFML/include
./include
)
if(UNIX)
set(BOOST_LIBRARY
-L./boost/linux
-lboost_regex
)
set(SFML_LIBRARY
-L./SFML/linux
-lsfml-graphics
-lsfml-window
-lsfml-system
)
add_executable(r-type_client
srcs/Main.cpp
)
target_link_libraries(r-type_client
${BOOST_LIBRARY}
${SFML_LIBRARY}
)
elseif(WIN32)
add_library(bar SHARED IMPORTED)
set_property(TARGET bar PROPERTY IMPORTED_LOCATION
C:/Users/Hugo/Downloads/Old/client/SFML/windows/sfml-graphics.dll)
set_property(TARGET bar PROPERTY IMPORTED_IMPLIB
C:/Users/Hugo/Downloads/Old/client/SFML/windows/sfml-graphics.lib)
add_library(bor SHARED IMPORTED)
set_property(TARGET bor PROPERTY IMPORTED_LOCATION
C:/Users/Hugo/Downloads/Old/client/SFML/windows/sfml-window.dll)
set_property(TARGET bor PROPERTY IMPORTED_IMPLIB
C:/Users/Hugo/Downloads/Old/client/SFML/windows/sfml-window.lib)
add_library(bur SHARED IMPORTED)
set_property(TARGET bur PROPERTY IMPORTED_LOCATION
C:/Users/Hugo/Downloads/Old/client/SFML/windows/sfml-system.dll)
set_property(TARGET bur PROPERTY IMPORTED_IMPLIB
C:/Users/Hugo/Downloads/Old/client/SFML/windows/sfml-system.lib)
add_executable(r-type_client srcs/Main.cpp)
target_link_libraries(r-type_client bar bor bur)
endif(UNIX)

Answer 1

As I've mentioned in the comments, you should set up your CMake project in a proper way by using find_package() to properly locate everything.
CMake is a tool to allow people to creation files needed for compilation on the fly no matter the host system. By hardcoding paths and (unneeded) per-platform branches, you're basically negating the whole purpose of CMake.
To include a third party library in CMake, you'll typically want to use find_package(), which includes the necessary logic to locate the library and setup variables properly (it essentially does what you've done by hand so far).
Let's do it for SFML, since it's basically the same for Boost (and I don't really have Boost ready to test everything, because the variable names might differ from project to project).
First, you'll tell CMake that your project wants to use SFML:
find_package(SFML)
Depending on the actual "package", you can extend this. In SFML's case we can even define which minimum version we want and which sub libraries we actually want to use:
find_package(SFML 2.3 COMPONENTS graphics window system REQUIRED)
The REQUIRED flag makes the whole thing mandatory, i.e. CMake will error out, if it's not found.
Once this line succeeded, it will have set a few variables with the proper paths and libraries, which we can then use when defining a target:
include_directories(${SFML_INCLUDE_DIR})
add_executable(myprogram ${MY_SOURCE_FILES})
target_link_libraries(myprogram ${SFML_LIBRARIES} ${SFML_DEPENDENCIES})
And you're done. As you can see, I can setup a CMake project in less than 10 lines without any platform specific paths, code, or knowledge.
However, when running this, you'll most likely run into one error:
CMake by default might not be able to find a FindSFML.cmake file and complain.
You'll find this file in your SFML directory under the cmake path. Copy it to your project and tell CMake where to look for it, for example:
set(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake")
Once this is done as well, CMake might not be able to locate the actual SFML files, especially on Windows. To tell it where to look for it, you'd define SFML_ROOT when invoking CMake:
cmake -DSFML_ROOT=C:/Users/Hugo/Downloads/Old/client/SFML path/to/source
This gives you the big advantage that you won't have to hardcode the path to SFML (or any other library such as Boost). On your linux machine, you typically won't even have to provide any path and everything should just work out of the box.