CODEWITHSUNDEEP
heap-memoryprogramming-languagescallstack
Cheeta
Cheeta

Reputation: 437

Heap-Dynamic or Stack-Dynamic?

Please explain to me if "x" is a Stack-Dynamic variable or Heap-Dynamic variable in this code?And if it is Heap-Dynamic then why it is not Stack-Dynamic variable?Thank you

function foo(){ MyClass x = new MyClass();}

Upvotes: 4

Views: 15433

Answers (3)

python
python

Reputation: 4521

Stack dynamic variables come into existence when you call a function. They exist on the C++ runtime stack, and are temporary. They are either in the parameter list, or declared inside the function (except for statics, which are not instantiated on the stack). These variables disappear when they go out of scope, and the memory for their contents is reclaimed by the runtime.

Heap dynamic instances exist in another area of memory the runtime sets aside called the "heap." These instances come into being via. the "new" operator, and must be explicitly deallocated by the "delete" operator.

I hope this is helpful

Upvotes: 8

Floris Velleman
Floris Velleman

Reputation: 4888

This specific one is: Dynamic-Heap (I'm assuming you're programming in JAVA here). As to why it's not on the stack?

  • This allocates memory
  • It's not an automatic variable

See this article for general directions: http://www.maxi-pedia.com/what+is+heap+and+stack

Upvotes: 1

Chris Eberle
Chris Eberle

Reputation: 48785

I'm not sure what language this is, I'm going to go out on a limb and say it's merely pseudo code, but the concepts should be the same across most of the common OO languages.

Let's break this down:

function foo() {
    MyClass x = null;
    x = new MyClass();
}

The first line MyClass x = null will allocate some space on the local stack. It's not a lot of space, just enough to store a reference.

The second line x = new MyClass() will do a few things:

  1. Allocate space on the heap for a new instance of MyClass
  2. Call the correct constructor for MyClass
  3. Change the x reference to point to this new instance.

So the simple answer is: it's both.

Upvotes: 3

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