OpenGL GLFW、三角形がレンダリングされない

macOSで三角形をレンダリングしようとしましたが、機能しません。

これが私のコードです：

#include <iostream>
#include <glm/glm.hpp>
#include <GL/glew.h>
#include <GLFW/glfw3.h>

void OnError(int errorCode, const char* msg){
    throw std::runtime_error(msg);
}

int main(){
    glfwSetErrorCallback(OnError);
    if (!glfwInit()){
        throw std::runtime_error("glfwInit failed");
    }
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
    glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);

    GLFWwindow* window = glfwCreateWindow(512, 512, "Title", NULL, NULL);
    if (!window){
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);

    glewExperimental = GL_TRUE;
    if (glewInit() != GLEW_OK){
        glfwTerminate();
        return -1;
    }

    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LESS);

    float points[] = {
        0.0, 0.5, 0.0,
        -0.5, -0.5, 0.0,
        0.5, -0.5, 0.0
    };

    GLuint vbo = 0;
    glGenBuffers(1, &vbo);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW);

    GLuint vao = 0;
    glGenBuffers(1, &vao);
    glBindVertexArray(vao);
    glDisableVertexAttribArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);

    const char* vertex_shader =
    "#version 410\n"
    "in vec3 vp;"
    "void main(){"
    " gl_Position = vec4(vp, 1.0);"
    " };";

    GLuint vs = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vs, 1, &vertex_shader, NULL);
    glCompileShader(vs);

    const char* fragment_shader =
    "#version 410\n"
    "out vec4 frag_colour;"
    "void main(){"
    " frag_colour = vec4(0.0, 1.0, 0.0, 1.0);"
    " };";

    GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fs, 1, &fragment_shader, NULL);
    glCompileShader(fs);

    GLuint shader_program = glCreateProgram();
    glAttachShader(shader_program, fs);
    glAttachShader(shader_program, vs);
    glLinkProgram(shader_program);

    while (!glfwWindowShouldClose(window)){
        //glViewport(0, 0, 512, 512);
        //glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        glUseProgram(shader_program);
        glBindVertexArray(vao);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glBindVertexArray(0);
        glfwSwapBuffers(window);

        glfwPollEvents();
        glClear(GL_COLOR_BUFFER_BIT);
        glEnableVertexAttribArray(0);
        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glDisableVertexAttribArray(0);
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glfwTerminate();
    return 0;
}