OpenGL without shaders - c++

Question

I have read some tutorials to write the following code.
The only difference is the original tutorials where using SDL instead of GLEW.
I do not understand what is wrong in this code. It compiles but i do not see the triangle. (the tutorial were not using shaders too)
#include <iostream>
#include <GL/glew.h>
#include <GL/gl.h>
#include <GLFW/glfw3.h>
GLFWwindow* window;
int main(int argc, const char * argv[])
{
if (!glfwInit())
{
return -1;
}
glfwWindowHint(GLFW_SAMPLES, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
window = glfwCreateWindow(640, 480, "Test", NULL, NULL);
if (window==NULL)
{
return -1;
}
glfwMakeContextCurrent(window);
glewExperimental = true;
if (glewInit() != GLEW_OK)
{
return -1;
}
glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
glClearColor(0.0f, 1.0f, 1.0f, 1.0f);
do
{
glfwPollEvents();
float vertices[] = {-0.5, -0.5, 0.0, 0.5, 0.5, -0.5};
glClear(GL_COLOR_BUFFER_BIT);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, vertices);
glEnableVertexAttribArray(0);
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(0);
glfwSwapBuffers(window);
}
while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS && glfwWindowShouldClose(window) == 0 );
glfwTerminate();
return 0;
}

Answer 1

If you're using the fixed-function pipeline, you cannot use generic vertex attributes like glVertexAttribPointer.
NVIDIA's implementation, however, illegally aliases between generic attributes and non-generic ones. This is probably why the initial writer of the tutorial got away with it on their machine.
If you want to write this in a cross-platform way, you have to use glVertexPointer and glEnableClientState:
glVertexPointer(2, GL_FLOAT, 0, vertices);
glEnableClientState(GL_VERTEX_ARRAY);