Is my assumption concerning how a reference type value is stored in the heap correct?

Question

1.00/5 (5 votes)

See more:

As I have been diving deep into the topic of boxing it got me rethinking on how reference type variables work, specifically in terms of how the value that is referenced by them is stored in the heap. This is a silly question but any clarification is appreciated.

public class Program
{
    public static void Main(string[] args)
    {
        CustomClassType inst1 = new CustomClassType();
    }
}

public class CustomClassType
{
    //body
}

Thus, concerning my above example: I am aware of what goes on on the left side of the assignment operator. However, it's what is on the right side that I am a bit confused on. Thus, my question is, when an instance of user-defined class type is CustomClassType is created, is the instance stored directly in the heap as is? Or is the instance stored in a box (per say, as with boxing a value type) and then stored in the Heap?

I am aware that a referece to something is assigned to variable inst1. However, it's about me trying to understand what that something is. In terms of if that something is an instance (stored in the heap) or if that something is a box (as with in boxing a value) storing an instnance.

And please include if the same applies to literal values of reference type (e.g. "Bill").

What I have tried:

Any kind of useful clarification is appreciate thanks.

Posted 22-May-21 12:21pm

Jake Samson

Updated 24-May-21 2:22am

v6

Add a Solution

Comments

[no name] 23-May-21 15:45pm

"Boxing" applies to value types; creating an object (reference type) to store on the heap. There is no (further) "boxing" of reference types; it would be pointless.

(The "string literal" seems to have an extra dimension ... the "string" table / pool).

[no name] 23-May-21 17:29pm

In that case are you implying that a value of Reference type is stored directly in the Heap (not stored in some box)? Thus, nothing like how a value that is boxed is stored in the Heap?

[no name] 24-May-21 0:32am

The reference type "is" the "box".

2 solutions

Solution 2

only value types are ever boxed. boxing is basically a thunk to allow a value type to be referred to with a double indirected GC pointer and thus tracked by the GC.

value types typically live on the stack so they are not tracked by the GC.

Boxing basically copies a value type from the stack onto the heap in a "box" which is "kind of" a wrapper for a value type (not really an actual wrapper, just a thunk with some bookkeeping info in it)

A class already lives on the heap. Therefore, a class never needs to be boxed. It already has the bookkeeping data in the 80 or so bytes of overhead that a class takes (if i remember correctly, but my memory is iffy on specifics)

And in terms of a reference to a boxed type it's double indirected internally just like a class pointer is (because it's managed by the GC), whereas again, a pointer to a value type on the stack doesn't have to be.

What I am telling you is all implementation details, and may change, or have been changed since I last looked.

Posted 24-May-21 2:22am

honey the codewitch

Updated 24-May-21 2:23am

v2

Comments

Richard Deeming 24-May-21 8:54am

Be warned, the OP has been kicked off for being a nasty little troll, and has re-spawned at least once so far to hurl abuse at the people who try to help him.

honey the codewitch 24-May-21 8:59am

If he does, he'll regret it. I didn't post the answer for him. I posted it because it was a good question. I half assumed he'd be kicked for the autism remark.

Dave Kreskowiak 24-May-21 9:32am

No, he won't. His kind never regrets the attempts at insults they throw.

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

BillWoodruff · Accepted Answer · 2021-05-22T19:06:00

Solution 1

I think you are over-thinking how Reference Types are stored. They go on the heap, and what you "get back" when you instantiate a Reference Type is a pointer to the in-memory location of the instance.

With Types String, Struct, and Enum, things get more complex in terms of internal storage.

See if you find this helpful: [^].

If you want a deeper dive into Type handling, see Eric Lippert's articles: [^], [^], [^] ,[^], [^]

Posted 22-May-21 19:06pm

BillWoodruff

Comments

[no name] 23-May-21 3:09am

In that case the value referenced by a Reference type variable is nothing like a value that is boxed?

In other words, are you saying that a value (whether it be a literal value or an instance) of reference type is stored directly in the Heap, in NO box (per say)? Thus, nothing like a value that is boxed, which is stored in a box (per say) then stored on heap?

BillWoodruff 23-May-21 3:59am

You have a choice to make: spend time studying the links I sent you and gain a basic knowledge of how Types are allocated, stored ... or, persist in lurching to and 'fro on the deck of a ship in a storm :) Boxing, and unboxing, are simple:

https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/types/boxing-and-unboxing

BillWoodruff 24-May-21 1:18am

Very entertaining :)

enhzflep 24-May-21 21:14pm

Indeed. Thanks for signposting the route to this fun little cul-de-sac.