To combine several answers and add my own, without a class definition the calling code doesn’t know: whether the class has a declared destructor, or if the default destructor is to be used, and if so whether the default destructor is trivial, whether the destructor is accessible to the calling code, what base classes exist … Read more
Rather then telling you when to use delete, I’ll try to explain why you use pointers anyway. So you can decide when to use dynamic objects, how to use them and so when to call delete (and not). Rules of thumb: Use static objects where possible, then when needed create a pointer to that instance. … Read more
Every use of new should be balanced by a delete, and every use of new[] should be balanced by delete[]. for(int i=0;i<N;i++) delete array[i]; delete[] array; That would be appropriate only if you initialized the array as: Objects **array = new Objects*[N]; for (int i = 0; i < N; i++) { array[i] = new … Read more
You get undefined behaviour if you try to delete an object through a pointer more than once. This means that pretty much anything can happen from ‘appearing to work’ to ‘crashing’ or something completely random.
The destructor of A will run when its lifetime is over. If you want its memory to be freed and the destructor run, you have to delete it if it was allocated on the heap. If it was allocated on the stack this happens automatically (i.e. when it goes out of scope; see RAII). If … Read more
Let’s talk about copying objects in C++. Test t;, calls the default constructor, which allocates a new array of integers. This is fine, and your expected behavior. Trouble comes when you push t into your queue using q.push(t). If you’re familiar with Java, C#, or almost any other object-oriented language, you might expect the object … Read more
1 & 2 myVar = 8; //not dynamically allocated. Can’t call delete on it. myPointer = new int; //dynamically allocated, can call delete on it. The first variable was allocated on the stack. You can call delete only on memory you allocated dynamically (on the heap) using the new operator. 3. myPointer = NULL; delete … Read more
No, it’s not guaranteed and an implementation may legitimately assign zero to an lvalue operand to delete. Bjarne Stroustrup had hoped that implementations would choose to do this, but not many do. http://www.stroustrup.com/bs_faq2.html#delete-zero
Base* p = new Base[n] creates an n-sized array of Base elements, of which p then points to the first element. Base* p = new Derived[n] however, creates an n-sized array of Derived elements. p then points to the Base subobject of the first element. p does not however refer to the first element of … Read more
5.3.5/7 says: If the value of the operand of the delete-expression is not a null pointer value, the delete-expression will call a deallocation function (3.7.4.2). Otherwise, it is unspecified whether the deallocation function will be called. And 3.7.4.2/3 says: The value of the first argument supplied to a deallocation function may be a null pointer … Read more