To reduce the likelihood of invalid file names 來減少出現(xiàn)無效文件名的可能性。
When a user sends an empty file or enters an invalid file name , the diamond operator returns the uninitialized defined value , causing a crash of the 當(dāng)用戶發(fā)送一個(gè)空文件或鍵入無效的文件名時(shí),菱形操作符返回未初始化定義的值,使