Should destructors be threadsafe?

Question

I was going through a legacy code and found the following snippet:

MyClass::~MyClass()
{
   EnterCriticalSection(&cs);

//Access Data Members, **NO Global** members are being accessed here


  LeaveCriticalSection(&cs);
}

I am wondering will it help by any chance to guard the destructor ?

Consider a scenario :

1. Thread1 - About to execute any of the member function which uses critical section
2. Thread2-  About to execute destructor.

If the order of execution is 1=>2 then it might work. But what if the order is reversed ?

Is it a design issue ?

Answer 1

The destructor should not be called when the object is in use. If you're dealing with such a situation, it needs a fundamental fix. However, the destructor might want to alter some other thing (which is unrelated to the class being destructed) and it might need a critical section (e.g. like decrementing a global counter).

Answer 2

I think you have a more fundamental problem. It shouldn't be legal to destroy your object on one thread while another thread is still calling member functions. This in itself is wrong.

Even if you successfully guard your destructor with critical sections, what happens when the other thread starts executing the remainder of the function? It will be doing so on a deleted object which (depending on it's allocation location) will be garbage memory or simple an invalid object.

You need to alter your code to ensure the object is not destructed while still in use.