When is 'delete' called on temporary objects created with `new`?

Question

I initialise the SmartPtr class with new Time(1,0,0).

    //main.cpp 
    int main()
{
    SmartPtr pTime0(new Time(0,0,1));
}

Nowhere am I calling delete on new Time(1,0,0). Everything works fine, the program complies and runs. but I am confused -- where should/should not I delete Time(1,0,0) ?

I do not understand the concept of temporary objects creating and deleting here. I know whenever I write new somewhere I MUST WRITE delete ! Could someone please explain where delete Time(1,0,0) takes place?

SmartPtr pTime0(new Time(0,0,1)) <-- new here returns a pointer to a newly allocated memory, and then in ctor I allocate new memory the second time??

//SmartPtr.cpp 

SmartPtr::SmartPtr(Pointee * p):_pointee(new Pointee(*p))
{}

SmartPtr::~SmartPtr()
{
    delete _pointee; 
}

Answer 1

I don't know the details of your SmartPtr class.

In any case, if you have a constructor like this:

SmartPtr::SmartPtr(Pointee * p):_pointee(new Pointee(*p))
{}

and this is the destructor:

SmartPtr::~SmartPtr()
{
    delete _pointee; 
}

then with this code:

SmartPtr pTime0(new Time(0,0,1));

you leak one instance of Time(0,0,1).

In fact, you have one more new than delete (2 news and 1 delete):

Step #1: You call new Time(0,0,1) and create a new object on the heap.
(new count == 1)

Step #2: You pass this pointer to SmartPtr constructor, which deep copies previously created object and allocates a new copy on the heap, and keeps track of this copy via its _pointee data member.
(new count == 2)

Step #3: When the SmartPtr destructor runs, it deletes the instance pointed by _pointee data member, but you leaked the firts Time(...) created on the heap with new Time(0,0,1).
(delete count == 1; new count == 2)

A possible fix for that could be to just have this constructor:

SmartPtr::SmartPtr(Pointee * p)
    : _pointee(p) // <--- transfer ownerhsip (no deep copies) !
{}

---

An easy way to identify potential leaks in these cases is to put some console tracing output in Time class constructors and destructor, and check that the trace output of destructor matches the ones of constructors, e.g.:

Time::Time(....)
{
    // Do construction work....

    std::cout << "Time constructor\n";
}

Time::~Time(....)
{
    // Do destructor work....

    std::cout << "Time destructor\n";
}

The total count of "Time constructor" strings should match the total count of "Time destructor" strings.