memory management - Is there a reason to call delete in C++ when a program is exiting anyway?

Question

In my C++ main function, for example, if I had a pointer to a variable which uses heap memory (as opposed to stack memory) - is this automatically deallocated after my application exits? I would assume so.

Even so, is it good practice to always delete heap allocations even if you think they will never be used in a situation where the memory is automatically deallocated on exit?

For example, is there any point in doing this?

int main(...)
{
    A* a = new A();
    a->DoSomething();
    delete a;
    return 0;
}

I was thinking maybe in case I refactor (or someone else refactors) that code and puts it elsewhere in the application, where delete is really necessary.

As well as the answer by Brian R. Bondy (which talks specifically about the implications in C++), Paul Tomblin also has a good answer to a C specific question, which also talks about the C++ destructor.

Answer 1

It is important to explicitly call delete because you may have some code in the destructor that you want to execute. Like maybe writing some data to a log file. If you let the OS free your memory for you, your code in your destructor will not be executed.

Most operating systems will deallocate the memory when your program ends. But it is good practice to deallocate it yourself and like I said above the OS won't call your destructor.

As for calling delete in general, yes you always want to call delete, or else you will have a memory leak in your program, which will lead to new allocations failing.