I have code:
Code :
    glLoadIdentity();
    visibleRect = [self visibleRect];
    glViewport(0, 0, NSWidth(visibleRect), NSHeight(visibleRect));
    glMatrixMode(GL_PROJECTION);
    glFrustum(NSMinX(visibleRect), NSMaxX(visibleRect), NSMinY(visibleRect), NSMaxY(visibleRect), 0.1, 100);
    glTranslatef(0,0,zoomValue);
    glClearColor(0.93, 0.93, 0.93, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);
 
    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, texture);
    glBegin(GL_QUADS);
    glTexCoord2f(0.0f, 0.0f); glVertex2f(0.0f, 0.0f);
    glTexCoord2f(0.0f, 1.0f); glVertex2f(0.0f, height);
    glTexCoord2f(1.0f, 1.0f); glVertex2f(width, height);
    glTexCoord2f(1.0f, 0.0f); glVertex2f(width, 0.0f);
    glEnd();
    glBindTexture(GL_TEXTURE_2D, 0);
 
    glFlush(); //Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)

And I get Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0) error at glFlush line.
Why does this error appears?