FreeGLUT glutMainLoopEvent() problem

#include <GL/freeglut.h> //uses freeGLUT extensions!

#include <iostream>

//switches between manual looping or GLUT's default event loop//////////////////
#define CUSTOMLOOP 1

#if CUSTOMLOOP == 1
    #define MAINLOOP while (1) glutMainLoopEvent()
#endif

#if CUSTOMLOOP == 0
    #define MAINLOOP glutMainLoop()
#endif
////////////////////////////////////////////////////////////////////////////////

//display function
void cback_render()
{
    static float rotations = 0;

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glLoadIdentity();
    glRotatef(rotations, 0, 0, 1);

    glBegin(GL_TRIANGLES);
        glVertex3f(0,0,0);
        glVertex3f(1,0,0);
        glVertex3f(0,1,0);
    glEnd();

    glutSwapBuffers();

    if (++rotations > 360) rotations -= 360;

//glutMainLoopEvent() never returns unless you force an update!!!
#if CUSTOMLOOP == 1
    glutPostRedisplay();
#endif
}

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH);
    glutInitWindowPosition(100, 100);
    glutInitWindowSize(512, 512);

    glutCreateWindow("freegluttest");
    glutDisplayFunc (cback_render);

//Don't need to provide an idle function if we're forcing redisplays ourselves
#if CUSTOMLOOP == 0
    glutIdleFunc(cback_render);
#endif

    //loop switch occurs here
    MAINLOOP;

    return 0;
}