预期的不合格错误ID Xcode C++GLFW GLAD

Question

我是Xcode OpenGl-Grad和C++的新手，我只是想让它编译，任何帮助都会很棒。我真的不明白该怎么处理这个错误，我在这里错过了什么？

#include <glad/glad.h>
#include <GLFW/glfw3.h>
{
int main()
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
//glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);

return 0;
}
GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
if (window == NULL)
{
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
glViewport(0, 0, 800, 600);
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
glViewport(0, 0, width, height);
}
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
while(!glfwWindowShouldClose(window))
{
glfwSwapBuffers(window);
glfwPollEvents();
}

glfwTerminate();
return 0;

Answer 1

80%的代码都不在中(主要也不在其他函数中(