OpenGL 3.2 Core Profile, GLFW, Mac OS X Lion

gistfile1.c

// The following code doesn't work on Mac OS X Lion
// (I don't know for other platforms):

#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <GL/glfw.h>


char *VS = "#version 150\n in vec2 position; void main() {gl_Position = vec4(position, 0.0, 1.0);}";
char *FS = "#version 150\n out vec4 fragColor; void main() {fragColor = vec4(1.0, 0.0, 0.0, 1.0);}";

// quad vertices
GLfloat quad[] = {-0.5, -0.5, 0.5, -0.5, 0.5,  0.5, -0.5,  0.5};
// quad indices
GLubyte indices[] = {0, 1, 2, 3};


GLuint vertex_buffer, element_buffer;
GLuint quad_program;


void initQuad (void) {
        // SHADERS -----------------------------------------------------------
        // vertex shader
        GLuint v_shader = glCreateShader(GL_VERTEX_SHADER);
        glShaderSource(v_shader, 1, (const GLchar**)&VS, 0);
        glCompileShader(v_shader);
        // fragment shader
        GLuint f_shader = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(f_shader, 1, (const GLchar**)&FS, 0);
        glCompileShader(f_shader);
        // quad program
        quad_program = glCreateProgram();
        glAttachShader(quad_program, v_shader);
        glAttachShader(quad_program, f_shader);
        glLinkProgram(quad_program);

        // BUFFERS -----------------------------------------------------------
        // vertex buffer (quad)
        glGenBuffers(1, &vertex_buffer);
        glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
        glBufferData(GL_ARRAY_BUFFER, sizeof(quad), quad, GL_STATIC_DRAW);
        // element buffer (indices)
        glGenBuffers(1, &element_buffer);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, element_buffer);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,
                GL_STATIC_DRAW);
}


void drawQuad (void) {
        // bind buffers
        glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, element_buffer);
        // bind shaders
        glUseProgram(quad_program);

        GLint pos = glGetAttribLocation(quad_program, "position");
        glVertexAttribPointer(pos, 2, GL_FLOAT, GL_FALSE, 0, (void*)0);

        // setup
        assert(glGetError() == GL_NO_ERROR); // no error here
        glEnableVertexAttribArray(pos);
        assert(glGetError() == GL_NO_ERROR); // ERROR: GL_INVALID_OPERATION

        // draw (GL_INVALID_OPERATION here too)
        glDrawElements(GL_TRIANGLE_FAN, 4, GL_UNSIGNED_BYTE, (void *)0);

        // cleanup (GL_INVALID_OPERATION here too)
        glDisableVertexAttribArray(pos);
}


int main (int argc, char const *argv[])
{
        glfwInit();
        glfwOpenWindowHint(GLFW_OPENGL_VERSION_MAJOR, 3);
        glfwOpenWindowHint(GLFW_OPENGL_VERSION_MINOR, 2);
        glfwOpenWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
        glfwOpenWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
        glfwOpenWindow(640, 480, 8, 8, 8, 8, 0, 0, GLFW_WINDOW);

        initQuad();

        while (!glfwGetKey(GLFW_KEY_ESC) && glfwGetWindowParam(GLFW_OPENED)) {
                glClear(GL_COLOR_BUFFER_BIT);
                drawQuad();
                glfwSwapBuffers();
        }

        glfwTerminate();
        exit(EXIT_SUCCESS);
}

I fail to understand. It works perfectly if I comment lines (78 .. 81) and adapt the shaders for version 120. However, with OpenGL 3.2 Core Profile, nothing is displayed (there should be a red quad on the screen).

Does anyone have a clue?

Well, I finally found my mistake: use a vertex array object!

GLuint vao; // declare this global variable
// ...
void initQuad (void)
{
        // ...
        glGenVertexArrays(1, &vao);
}

void drawQuad (void)
{
        glBindVertexArray(vao);
        // ...
}

Can you please share the working code?

The following should work (although I didn't run it):

https://gist.github.com/1401335