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string * str=new string;
delete str;
when I delete 'str' which points to an object, do two destructors get called - one for the pointer itself, and one for the object it points to?
What would the pointer's destructor do?
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The smart pointer destructor contains the call to delete, and because the smart pointer is declared on the stack, its destructor is invoked when the smart pointer goes out of scope, even if an exception is thrown somewhere further up the stack.
Default destructors call destructors of member objects, but do NOT delete pointers to objects.
Boost smart pointers by themselves don't have anything to do with the need for a destructor. All they do is remove the need for you to call delete on the allocated memory that they are effectively managing.
Pointers to variables on the stack do not need to be deleted. They become invalid on their own when the function the variable is in returns. Pointers to memory created using new should be deleted using delete .
delete just causes the object that the given pointer is pointing at to be destroyed (in this case, the string object. The pointer itself, denoted by str, has automatic storage duration and will be destroyed when it goes out of scope like any other local variable.
Note, however, that non-class types do not have destructors. So even when you use delete with non-class types, no destructor is called, but when the pointer goes out of scope, it gets destroyed as normally happens with any other automatic variable (means the pointer just reaches the end of its lifetime, though the memory pointed to by the pointer is not deallocated until you use delete to explicitly deallocate it.).
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