my code

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

static unsigned int CompileShader(unsigned int type, const std::string& source)
{
	unsigned int id = glCreateShader(type);
	const char* src = source.c_str();
	glShaderSource(id, 1, &src, nullptr);
	glCompileShader(id);

	int result;
	glGetShaderiv(id, GL_COMPILE_STATUS, &result);
	if (result == GL_FALSE)
	{
		int length;
		glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
		char* message = (char*)alloca(length * sizeof(char));
		glGetShaderInfoLog(id, length, &length, message);
		std::cout << "Failed to compile " << (type == GL_VERTEX_SHADER ? "vertex" : "fragment")<<
			std::endl;
		std::cout << message << std::endl;
		glDeleteShader(id);
		return 0;
	}

	return id;
}

static unsigned int CreateShader(const std::string& vertexShader, const std::string& fragmentShader)
{
	unsigned int program = glCreateProgram();
	unsigned int vs = glCreateShader(GL_VERTEX_SHADER);
	unsigned int fs = glCreateShader(GL_VERTEX_SHADER);

	glAttachShader(program, vs);
	glAttachShader(program, fs);
	glLinkProgram(program);
	glValidateProgram(program);

	glDeleteShader(vs);
	glDeleteShader(vs);

	return program;
}
int main(void)
{
	GLFWwindow* window;

	/* Initialize the library */
	if (!glfwInit())
		return -1;

	/* Create a windowed mode window and its OpenGL context */
	window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
	if (!window)
	{
		glfwTerminate();
		return -1;
	}

	/* Make the window's context current */
	glfwMakeContextCurrent(window);


	if (glewInit() != GLEW_OK)
	{
		std::cout << "error" << std::endl;
	}

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

	float positions[6] = {
		-0.5f, -0.5f,
		0.0f, 0.5f,
		0.5f, -0.5F

	};

	unsigned int buffer;
	glGenBuffers(1, &buffer);
	glBindBuffer(GL_ARRAY_BUFFER, buffer);
	glBufferData(GL_ARRAY_BUFFER, 6 * sizeof(float), positions, GL_STATIC_DRAW);

	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 2, 0);

	glBindBuffer(GL_ARRAY_BUFFER, 0);

	std::string vertexShader =
		"#version 330 core\n"
		"\n"
		"layout(location = 0)in vec4 position;\n"
		"\n"
		"void main()\n"
		"{\n"
		"	gl_Position = position;\n"
		"}\n";

	std::string fragmentShader =
		"#version 330 core\n"
		"\n"
		"layout(location = 0)in vec4 color;\n"
		"\n"
		"void main()\n"
		"{\n"
		"	color = vec4(1.0, 0.0, 0.0, 1.0);\n"
		"}\n";

		unsigned int shader = CreateShader(vertexShader, fragmentShader);
		glUseProgram(shader);

	/* Loop until the user closes the window */
	while (!glfwWindowShouldClose(window))
	{
		/* Render here */
		glClear(GL_COLOR_BUFFER_BIT);

		glDrawArrays(GL_TRIANGLES, 0, 3);

		/* Swap front and back buffers */
		glfwSwapBuffers(window);

		/* Poll for and process events */
		glfwPollEvents();
	}

	glfwTerminate();
	return 0;
}