c ++中构造函数和析构函数的执行顺序

Question

我有c ++的小代码,有构造函数和析构函数.

#include <iostream> 
using namespace std; 
class K { 
public: 
    K(){cout<< "3 ";} 
    ~K(){cout<< "1 ";} 
}; 
int main() 
{ 
    { 
        K a; 
        { 
            K b; 
        } 
        { 
            K c; 
        } 
    } 
    system("pause"); 
    return 0; 
}

问题: 我不明白为什么答案是:331311

而不是:333111.

我知道第一次运行构造函数和最后的析构函数但是反转.

Answer 1

如果正确对齐,您的代码将更容易理解:

int main() 
{ 
    { 
        K a;  // a is being constructed
        { 
            K b; // b is being constructed
        } // b is being destructed
        { 
            K c; // c is being constructed
        } // c is being destructed
    } // a is being destructed

    system("pause");
    return 0; 
}

一般规则是,本地(自动)分配的变量仅存在于其范围内.

{
    SomeType a; // Creation
} // all local variables from matching { are destroyed