Hola Mundo II

Este si lo considero un "Hola Mundo" en condiciones, de hecho quizá se pasa un poco.
Cuando lo ejecutéis debería salir una ventana en color rojo, a los dos segundos cambiarse a verde y después a azul. Por último se cierra y termina el programa.
No me voy a parar a explicarlo, esto simplemente es para ver que lo tenemos bien configurado y que funciona.

#include <stdio.h>
#include <stdio.h>
#include <stdlib.h>
/* If using gl3.h */
/* Ensure we are using opengl's core profile only */
#include <GL/gl.h>

#include <SDL2/SDL.h>
#define PROGRAM_NAME "Tutorial1"

/* A simple function that prints a message, the error code returned by SDL,
 * and quits the application */
void sdldie(const char *msg) {
    printf("%s: %s\n", msg, SDL_GetError());
    SDL_Quit();
    exit(1);
}

void checkSDLError(int line = -1) {
#ifndef NDEBUG
    const char *error = SDL_GetError();
    if (*error != '\0') {
        printf("SDL Error: %s\n", error);
        if (line != -1)
            printf(" + line: %i\n", line);
        SDL_ClearError();
    }
#endif
}

/* Our program's entry point */
int main(int argc, char *argv[]) {
    SDL_Window *mainwindow; /* Our window handle */
    SDL_GLContext maincontext; /* Our opengl context handle */

    if (SDL_Init(SDL_INIT_VIDEO) < 0) /* Initialize SDL's Video subsystem */
        sdldie("Unable to initialize SDL"); /* Or die on error */

    /* Request opengl 3.2 context.
     * SDL doesn't have the ability to choose which profile at this time of writing,
     * but it should default to the core profile */
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);

    /* Turn on double buffering with a 24bit Z buffer.
     * You may need to change this to 16 or 32 for your system */
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 32);

    /* Create our window centered at 512x512 resolution */
    mainwindow = SDL_CreateWindow(PROGRAM_NAME, SDL_WINDOWPOS_CENTERED,
    SDL_WINDOWPOS_CENTERED, 512, 512, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);
    if (!mainwindow) /* Die if creation failed */
        sdldie("Unable to create window");

    checkSDLError(__LINE__);

    /* Create our opengl context and attach it to our window */
    maincontext = SDL_GL_CreateContext(mainwindow);
    checkSDLError(__LINE__);

    /* This makes our buffer swap syncronized with the monitor's vertical refresh */
    SDL_GL_SetSwapInterval(1);

    /* Clear our buffer with a red background */
    glClearColor(1.0, 0.0, 0.0, 1.0);
    glClear( GL_COLOR_BUFFER_BIT);
    /* Swap our back buffer to the front */
    SDL_GL_SwapWindow(mainwindow);
    /* Wait 2 seconds */
    SDL_Delay(2000);

    /* Same as above, but green */
    glClearColor(0.0, 1.0, 0.0, 1.0);
    glClear( GL_COLOR_BUFFER_BIT);
    SDL_GL_SwapWindow(mainwindow);
    SDL_Delay(2000);

    /* Same as above, but blue */
    glClearColor(0.0, 0.0, 1.0, 1.0);
    glClear( GL_COLOR_BUFFER_BIT);
    SDL_GL_SwapWindow(mainwindow);
    SDL_Delay(2000);

    /* Delete our opengl context, destroy our window, and shutdown SDL */
    SDL_GL_DeleteContext(maincontext);
    SDL_DestroyWindow(mainwindow);
    SDL_Quit();

    return 0;
}