Pygame 窗口几秒钟后没有响应

This simple piece of code crashes (the window is not responding) after a few seconds (around 5).

import pygame
from pygame.locals import *

pygame.init()
screen = pygame.display.set_mode((640, 480), 0, 24)
#clock = pygame.time.Clock()

#font = pygame.font.Font(None, 32)

cycles = 0
while True:
    screen.fill(0)
#    text = font.render('Cycles : %d' % cycles, True, (255, 255, 255))
#    screen.blit(text, (100, 100))

    cycles += 1

    pygame.display.update()

如果我取消注释注释行，我可以清楚地看到程序在显示 47 到 50 之间的值时失控.