为什么析构函数被两次调用时我的程序不会崩溃

Question

The code below is:

#include <iostream>
using namespace std;

class A
{
public:
    A() {}
    ~A()
    {
        cout << "in destructor" << endl;
    }
};
void main()
{
    A a;
    a.~A();
}

has the following output:

in destructor
in destructor

Why my app does not crash if the destructed object is destructed again?

Answer 1

C++ Standard, section § 12.4 [destructors]

Once a destructor is invoked for an object, the object no longer exists; the behavior is undefined if the destructor is invoked for an object whose lifetime has ended ( 3.8 ). [ Example: if the destructor for an automatic object is explicitly invoked, and the block is subsequently left in a manner that would ordinarily invoke implicit destruction of the object, the behavior is undefined.

So your program has undefined behavior , it could crash now, later, never, earth could stop spinning etc... don't do it.

Note:

• void main() must be int main()