bss段的全称是block started by symbol，可读可写，见百度百科 http://baike.baidu.com/link?url=8jr3UHFxmINEmMAXEwLFD9N2VK5YlFGDWEpoR2UMSRIyT8hCUnmlv9k4q-Qv_lCY8ZmzAh3HvzbTl54Imo3A6q .i……
