[SOLVED] Cmake: Fetch content and link dependency

Cmake: Fetch content and link dependency

I use FetchContent to get the library (GLFW) and try to use dependencies inside the "deps" folder.

Here my file structure:

├── CMakeLists.txt
├── main.cpp
├── build
├── cmake
│   └── AddGLFW.cmake

CMakeLists.txt

cmake_minimum_required(VERSION 3.20)

project(Test1)

list(APPEND CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake")

include(AddGLFW)

include_directories("${GLFW_SOURCE_DIR}/deps")

set(GLAD_GL "${GLFW_SOURCE_DIR}/deps/glad/gl.h")

add_executable(main WIN32 main.cpp ${GLAD_GL})

target_link_libraries(main glfw)

AddGLFW.cmake

include(FetchContent)
FetchContent_Declare (
    glfw
    GIT_REPOSITORY https://github.com/glfw/glfw.git
    GIT_TAG 3.4
)

set(GLFW_BUILD_DOCS OFF CACHE BOOL  "")
set(GLFW_INSTALL OFF CACHE BOOL  "")

FetchContent_MakeAvailable(glfw)

main.cpp

#include "glad/gl.h"
#include "GLFW/glfw3.h"
#include <iostream>

int main() {
    GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
    glfwMakeContextCurrent(window);

    int version = gladLoadGL(glfwGetProcAddress);
    if (version == 0) {
        printf("Failed to initialize OpenGL context\n");
        return -1;
    }

    // Successfully loaded OpenGL
    printf("Loaded OpenGL %d.%d\n", GLAD_VERSION_MAJOR(version), GLAD_VERSION_MINOR(version));

}

When I build my project with cmake, there's a error "undefined reference to gladLoadGL", I don't know what go wrong hear, please help.

Solution

When use header glad/gl.h shipped with GLFW, you need to define the macro GLAD_GL_IMPLEMENTATION for obtain definition of functions in that header:

#define GLAD_GL_IMPLEMENTATION
#include "glad/gl.h"

(If you use that header from several sources of your application, then only one source should define that macro.)