類的構造函數中異常處理的行爲

我有這個程序，派生類的ctor拋出異常。該程序只是一個示例程序，我只是想了解異常處理的概念。類的構造函數中異常處理的行爲

class A{ 
public: 
    A() {} 

    ~A(){std::cout << "DTOR called - A!!" << std::endl;} 
}; 

class B : public A 
{ 
public: 
    B():A() 
    { 
     try 
     { 
     init(); 
     } 
     catch(...) 
     { 
     std::cout << "Inside catch block in B's Ctor!!" << std::endl; 
     throw this; 
     } 
    } 

    void init() { throw 0; } 

    ~B() {std::cout << "DTOR called - B!!" << std::endl; } 
}; 

int main() 
{ 
    try{ 
     B *b = new B; 

     std::cout << "Äfter B's ctor called in try block!!" << std::endl; 
     delete b; 
     std::cout << "Äfter B's dtor called in try block!!" << std::endl; 
    } 

    catch(B* b) 
    { 
     delete b; 
     b = NULL; 
     std::cout << "Exception Occurred in B!!" << std::endl; 
    } 

    catch(A* a) 
    { 
     delete a; 
     a = NULL; 
     std::cout << "Exception Occurred in A!!" << std::endl; 
    } 

    catch(...) 
    { 
     std::cout << "Exception Occured!!" << std::endl; 
    } 
    return EXIT_SUCCESS; 
}

預期的輸出是它應該進入B的catch塊，並且應該調用第一個B的dtor，然後調用A的dtor。但上述程序的輸出是：

Inside catch block in B's Ctor!! 
DTOR called - A!! 
DTOR called - B!! 
DTOR called - A!! 
Exception Occurred in B!!

我想問這是爲什麼A類的析構函數調用了兩次，當它只是引入了B類的catch塊，並呼籲只有B類的析構函數？也請告訴我是否在這裏犯了一些錯誤。任何幫助表示讚賞

編輯：

class B : public A 
{ 
public: 
    B():A() 
    { 
     try 
     { 
     szName = new char[100]; 
     init(); 
     } 
     catch(...) 
     { 
     std::cout << "Inside catch block in B's Ctor!!" << std::endl; 
     throw this; 
     } 
    } 

    void init() { throw 0; } 

    ~B() 
    { 
     delete szName; 
     std::cout << "DTOR called - B!!" << std::endl; 
    } 

    char *szName; 
};

在這裏，我在構造函數try塊創建了一個字符指針類B.分配的內存被拋出異常之前。現在在這種情況下，如果我沒有發現類B的異常，會不會有內存泄漏？

來源

2014-10-07 Saurabh Bhola

見http://www.gotw.ca/gotw/066.htm – 2014-10-07 06:33:29