windowless opengl context C++

void createWindowlessOpenGLContext()
{
    static glXCreateContextAttribsARBProc glXCreateContextAttribsARB = NULL;
    static glXMakeContextCurrentARBProc   glXMakeContextCurrentARB   = NULL;

    glXCreateContextAttribsARB = (glXCreateContextAttribsARBProc) glXGetProcAddressARB( (const GLubyte *) "glXCreateContextAttribsARB" );
    glXMakeContextCurrentARB   = (glXMakeContextCurrentARBProc)   glXGetProcAddressARB( (const GLubyte *) "glXMakeContextCurrent"      );
    CV_Assert(glXCreateContextAttribsARB != 0);
    CV_Assert(glXMakeContextCurrentARB != 0);

    const char *displayName = NULL;
    Display* display = XOpenDisplay( displayName );
    CV_Assert(display != 0);

    static int visualAttribs[] = { None };
    int numberOfFramebufferConfigurations = 0;
    GLXFBConfig* fbConfigs = glXChooseFBConfig( display, DefaultScreen(display), visualAttribs, &numberOfFramebufferConfigurations );
    CV_Assert(fbConfigs != 0);

    int context_attribs[] = {
        GLX_CONTEXT_MAJOR_VERSION_ARB, 3,
        GLX_CONTEXT_MINOR_VERSION_ARB, 3,
        GLX_CONTEXT_FLAGS_ARB, GLX_CONTEXT_CORE_PROFILE_BIT_ARB,
        //    GLX_CONTEXT_FLAGS_ARB, GLX_CONTEXT_DEBUG_BIT_ARB,
        //    GLX_CONTEXT_PROFILE_MASK_ARB, GLX_CONTEXT_CORE_PROFILE_BIT_ARB,
        None
    };

    GLXContext openGLContext = glXCreateContextAttribsARB( display, fbConfigs[0], 0, True, context_attribs);


    int pbufferAttribs[] = {
        GLX_PBUFFER_WIDTH,  32,
        GLX_PBUFFER_HEIGHT, 32,
        None
    };
    GLXPbuffer pbuffer = glXCreatePbuffer( display, fbConfigs[0], pbufferAttribs );

    XFree( fbConfigs );
    XSync( display, False );

    if ( !glXMakeContextCurrent( display, pbuffer, pbuffer, openGLContext ) )
    {
        CV_Assert(false);
    }
}