Object-Oriented Suicide or delete this;

Question

The following code compiled with MSVC9.0 runs and outputs Destructor four times, which is logical.

#include <iostream>
class SomeClass
{
public:
   void CommitSuicide()
   {
      delete this;
   }
   void Reincarnate()
   {
      this->~SomeClass();
      new (this) SomeClass;
   }
   ~SomeClass()
   {
      std::cout  << "Destructor\n";
   }
};

int main()
{
   SomeClass* p = new SomeClass;
   p->CommitSuicide();
   p =  new SomeClass;
   p->Reincarnate();
   p->~SomeClass(); //line 5
   p->CommitSuicide();
}

I think the first 4 lines of code in main do not result in undefined behavior (although not entirely sure about the delete this; thing). I would like to have a confirmation or < placeholder for confirmation's antonym > of that. But I have serious doubts about lines 5 and 6. It is allowed to explicitly call the destructor, isn't it? But is the lifetime of the object considered to have finished after that? That is, is invocation of another member after the explicit call of the destructor allowed (defined)?

To summarize, which parts of the above code (if any) result in undefined behavior (technically speaking)?

But the constructor is only called 3 times, so how is calling the destructor 4 times logical? It would bomb as soon as the class gets (non-trivial) data members. — visitor
< placeholder for confirmation's antonym > - it's called "denial" — slashmais

Jerry Coffin Jerry Coffin · Accepted Answer · 2010-10-18T13:43:45

The delete this; is fine. The last p->CommitSuicide(); gives undefined behavior because you already destroyed the object in "line 5".

Object-Oriented Suicide or delete this;

3 Answers