问std::cout << glGetString(GL_RENDER) << std::endl；抛出一个错误，但没有抛出GL_Renderer或GL_Verision，并且我找不出原因？

EN

#include "src/graphics/window.h"

int main()
{
    using namespace FutureGamingEngine;
    using namespace graphics;



    Window window("Test", 1080, 720);
    glClearColor(0, 255, 0, 1.0f); //Red, Green, Blue, No Idea

    std::cout << glGetString(GL_VERSION) << std::endl;
    std::cout << glGetString(GL_RENDERER) << std::endl;
    std::cout << glGetString(GL_RENDER) << std::endl;



    while (!window.closed())
    {


        window.clear();

        glBegin(GL_QUADS);
        glVertex2f(-0.5f, -0.5f);
        glVertex2f(-0.5f, 0.5f);
        glVertex2f(0.5f, 0.5f);
        glVertex2f(0.5f,-0.5f);
        glEnd();
        window.update();
    }

    //system("PAUSE");

    return 0;
}

#include "window.h"

namespace FutureGamingEngine
{
    namespace graphics
    {

        void windowResize(GLFWwindow *window, int width, int height);

        Window::Window(const char *title, int width, int height)
        {
            c_title = title;
            c_height = height;
            c_width = width;
            if (!init())
            {
                glfwTerminate();
            }
        }

        Window::~Window()
        {
            glfwTerminate();
        }

        bool Window::init()
        {
            glewExperimental = true;

            if (!glfwInit())
            {
                std::cout << "Error Code: 0" << std::endl;
                return false;
            }


            //Create a windowed mode and it's OpenGl Content
            c_window = glfwCreateWindow(c_width, c_height, c_title, NULL, NULL);

            //If we fail to make the window Terminate OpenGL
            if (!c_window)
            {
                glfwTerminate();
                return false;
            }

            //std::cout << "Open GL: " <<  glGetString(GL_VERSION) << std::endl;

            glfwMakeContextCurrent(c_window);
            glfwSetWindowSizeCallback(c_window, windowResize);

            if (glewInit() != GLEW_OK)
            {
                std::cout << "Error Code: 1" << std::endl;
                return false;
            }       


            return true;

        }

        bool Window::closed() const
        {
            return glfwWindowShouldClose(c_window);
        }

        void Window::update()
        {
            //poll for and process events
            glfwPollEvents();

            glfwGetFramebufferSize(c_window, &c_width, &c_height);

            //swap front and backbuffers
            glfwSwapBuffers(c_window);
        }

        void Window::clear() const
        {
            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        }

        void windowResize(GLFWwindow *window, int width, int height)
        {
            glViewport(0, 0, width, height);
        }
    }
}

#pragma once

#define GLEW_STATIC
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>

namespace FutureGamingEngine 
{
    namespace graphics
    {
        class Window
        {
        private:
            const char *c_title;
            int c_width, c_height;
            GLFWwindow *c_window;
            bool c_closed;
        public:
            Window(const char *a_name, int a_width, int a_height);
            ~Window();
            bool closed() const;
            void update();
            void clear() const;

            inline int getHeight() const { return c_height; };
            inline int getWidth() const { return c_width; };

        private:
            bool init();


        };
    }

}