CODEWITHSUNDEEP
c++cmakelibraries
Jason
Jason

Reputation: 2288

How do I properly link my libraries in my project using CMake?

I'm currently learning CMake and I'm trying to create my first test project. I'm able to get a simple project up and running in visual studio via CMake. However, I'm having trouble trying to add a library. I've read some guides and things but I keep getting errors. Basically, I'm trying to link SDL libraries (a game programming library) in my sample project. I've placed these libraries in a top level, 'ThirdParty' folder. Here is what my CmakeLists.txt file looks like in my top level directory:

cmake_minimum_required(VERSION 2.8.11)

project(Hello)

#Find necessary header files
find_path(SDL_INCLUDE_DIR SDL.h HINTS ${CMAKE_SOURCE_DIR}/ThirdParty/SDL2/include/)

#Find necessary library files
find_library(SDL_LIB_DIR SDL2 HINTS ${CMAKE_SOURCE_DIR}/ThirdParty/SDL2/lib/x86)
find_library(SDLMAIN_LIB_DIR SDLmain HINTS ${CMAKE_SOURCE_DIR}/ThirdParty/SDL2/lib/x86)

#Add/Link files to project
include_directories(${SDL_INCLUDE_DIR})
target_link_libraries(Test PUBLIC ${SDL_LIB_DIR})
target_link_libraries(Test PUBLIC ${SDLMAIN_LIB_DIR})



add_executable(Test "${CMAKE_SOURCE_DIR}/Source/Main.cpp")

I'm not 100 percent sure of the HINTS parameter, but I saw it used on another thread. Anyway, here's the error I keep getting:

CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
SDLMAIN_LIB_DIR
    linked by target "Test" in directory C:/Users/Jason/Desktop/Test

What am I doing wrong and how do I properly link libraries in CMake?

Upvotes: 0

Views: 967

Answers (1)

The Quantum Physicist
The Quantum Physicist

Reputation: 26356

  1. In cmake, you first create the executable, and then you link it to a library
  2. You have to understand how finding libraries and packages works in CMake. Typically the way it works is that you use find_library or find_package, and then cmake will set some variables that you can use to link to/use the library.

I'm not familiar with SDL, but by googling a little bit about it, I would say this is how it should look like:

find_file(SDL2_INCLUDE_DIR NAME SDL.h HINTS SDL2)
find_library(SDL2_LIBRARY NAME SDL2)
add_executable(MyExec main.cpp)
target_include_directories(MyExec ${SDL2_INCLUDE_DIR})
target_link_libraries(MyExec ${SDL2_LIBRARY})

That find_library will set the variables SDL2_INCLUDE_DIR and SDL2_LIBRARY, which you can use to link to SDL and add its includes to your project.

Upvotes: 2

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