問題描述
可能的重復(fù):
在 C++ 中通過指針捕獲異常
我總是按值捕獲異常.例如
I always catch exceptions by value. e.g
try{
...
}
catch(CustomException e){
...
}
但我遇到了一些用 catch(CustomException &e) 代替的代碼.這是 a) 好的 b) 錯(cuò)誤的 c) 灰色區(qū)域嗎?
But I came across some code that instead had catch(CustomException &e) instead. Is this a)fine b)wrong c)a grey area?
推薦答案
C++ 中異常的標(biāo)準(zhǔn)做法是......
The standard practice for exceptions in C++ is ...
按值拋出，按引用捕獲
在繼承層次結(jié)構(gòu)面前，按值捕獲是有問題的.假設(shè)對(duì)于您的示例，還有另一種類型 MyException 繼承自 CustomException 并覆蓋錯(cuò)誤代碼等項(xiàng)目.如果拋出 MyException 類型，您的 catch 塊將導(dǎo)致它被轉(zhuǎn)換為一個(gè) CustomException 實(shí)例，這將導(dǎo)致錯(cuò)誤代碼發(fā)生變化.
Catching by value is problematic in the face of inheritance hierarchies. Suppose for your example that there is another type MyException which inherits from CustomException and overrides items like an error code. If a MyException type was thrown your catch block would cause it to be converted to a CustomException instance which would cause the error code to change.
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