CMake linker not working correctly - c++

Question

I am trying to build my project using CMake but I am having error linking required libraries. I have this CMakeLists.txt in the root folder of my project:
cmake_minimum_required(VERSION 2.6)
project(test)
add_subdirectory(src)
And in my src folder, alongside my source files I have this CMakeLists.txt:
set (CMAKE_CXX_FLAGS "Wall -std=c++11" )
set (CMAKE_EXE_LINKER_FLAGS "-lSDL2 -lGL" )
file (GLOB SRCS *.cpp *.h )
add_executable(engine ${SRCS} )
I then go into the build folder and do cmake .. and it runs without any errors. When I do make, the compilation runs without any errors as well, but when it gets to the linking part, I get these errors:
CMakeFiles/test.dir/Application.cpp.o: In function `Application::onExecute()':
Application.cpp:(.text+0x41): undefined reference to `SDL_GetTicks'
Application.cpp:(.text+0x4e): undefined reference to `SDL_GetTicks'
Application.cpp:(.text+0xd7): undefined reference to `SDL_PollEvent'
CMakeFiles/test.dir/Application.cpp.o: In function `Application::render()':
Application.cpp:(.text+0x17b): undefined reference to `glClearColor'
Application.cpp:(.text+0x185): undefined reference to `glClear'
Application.cpp:(.text+0x194): undefined reference to `SDL_GL_SwapWindow'
CMakeFiles/test.dir/Application.cpp.o: In function `Application::cleanUp()':
Application.cpp:(.text+0x1b2): undefined reference to `SDL_GL_DeleteContext'
Application.cpp:(.text+0x1c1): undefined reference to `SDL_DestroyWindow'
Application.cpp:(.text+0x1c6): undefined reference to `SDL_Quit'
CMakeFiles/test.dir/Application.cpp.o: In function `Application::initialize()':
Application.cpp:(.text+0x1de): undefined reference to `SDL_Init'
Application.cpp:(.text+0x1ea): undefined reference to `SDL_GetError'
Application.cpp:(.text+0x22b): undefined reference to `SDL_CreateWindow'
Application.cpp:(.text+0x243): undefined reference to `SDL_GetError'
Application.cpp:(.text+0x25a): undefined reference to `SDL_Quit'
Application.cpp:(.text+0x270): undefined reference to `SDL_GL_SetAttribute'
Application.cpp:(.text+0x27f): undefined reference to `SDL_GL_SetAttribute'
Application.cpp:(.text+0x28e): undefined reference to `SDL_GL_SetAttribute'
Application.cpp:(.text+0x29d): undefined reference to `SDL_GL_CreateContext'
Application.cpp:(.text+0x2af): undefined reference to `glGetString'
collect2: error: ld returned 1 exit status
make[2]: *** [src/test] Error 1
make[1]: *** [src/CMakeFiles/test.dir/all] Error 2
make: *** [all] Error 2
I have the correct includes in my header files and I was able to compile and run using only make so I think the linker flags I tell CMake aren't being passed to the compiler. How can I fix this?

Answer 1

You have to use the cmake command target_link_libraries to reference SDL libs.