Deleting object with private destructor

Question

How is that possible that it is allowed to delete object with private destructor in the following code? I've reduced real program to the following sample, but it still compiles and works.

class SomeClass;

int main(int argc, char *argv[])
{
  SomeClass* boo = 0; // in real program it will be valid pointer
  delete boo; // how it can work?

  return -1;
}

class SomeClass
{
private:
  ~SomeClass() {}; // ! private destructor !
};

Answer 1

You are trying to delete object of incomplete class type. C++ Standard says that you'll get undefined behavior in this case (5.3.5/5):

If the object being deleted has incomplete class type at the point of deletion and the complete class has a non-trivial destructor or a deallocation function, the behavior is undefined.

To detect such cases you could use boost::checked_delete:

template<typename T> 
inline void checked_delete( T* p )
{
    typedef char type_must_be_complete[ sizeof(T)? 1: -1 ];
    (void) sizeof(type_must_be_complete);
    delete p;
}