Stack vs heap

[Benny]

DataSet ds = new DataSet()

Is the variable (pointer) 'ds' in the stack and the dataset object being pointed allocated in the heap

Thanks
Benny

[Vadym Stetsyak]

yes, DataSet object resides in the heap and 'pointer' is on the stack
if you wont preserve that pointer (as method return value) the pointer will
be lost thus leading to DataSet object collection by GC

"Benny" <an*******@disc ussions.microso ft.com> wrote in message
news:90******** *************** ***********@mic rosoft.com...

DataSet ds = new DataSet();

Is the variable (pointer) 'ds' in the stack and the dataset object being pointed allocated in the heap?
Thanks,
Benny

[Jon Skeet [C# MVP]]

Benny <an*******@disc ussions.microso ft.com> wrote:

DataSet ds = new DataSet();

Is the variable (pointer) 'ds' in the stack and the dataset object being
pointed allocated in the heap?

The DataSet itself is definitely on the heap. If ds is a local variable
within a method, it's on the stack. If it's a class or instance
variable, it's on the heap too.

See http://www.pobox.com/~skeet/csharp/memory.html for more
information.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Miha Markic [MVP C#]]

"Vadym Stetsyak" <pd****@ukr.net > wrote in message
news:e2******** ******@TK2MSFTN GP11.phx.gbl...

yes, DataSet object resides in the heap and 'pointer' is on the stack
if you wont preserve that pointer (as method return value) the pointer will be lost thus leading to DataSet object collection by GC

Just a note that reference can be preserved in other ways, for example
storing it as class scope field.

--
Miha Markic [MVP C#] - RightHand .NET consulting & software development
miha at rthand com
www.rthand.com

[Rakesh]

If that is the case, why is it being said that static methods can't access instance variables

Static methods will be in the stack right (or is it?). And the instance pointers will be in the stack too. So isn't it possible for static methods to 'indirectly' access instance variables through the instace pointers in the stack?

[Jon Skeet [C# MVP]]

Rakesh <an*******@disc ussions.microso ft.com> wrote:

If that is the case, why is it being said that static methods can't
access instance variables?

Static methods will be in the stack right (or is it?).
What exactly do you mean by this?
And the instance pointers will be in the stack too.
Or this?
So isn't it possible for static methods to 'indirectly' access
instance variables through the instace pointers in the stack?

I think you really need to explain carefully exactly what you mean.
Here's an example program which you should think about:

using System;

class Test
{
int x;

Test (int x)
{
this.x = x;
}

static void Main()
{
Test t1 = new Test(5);
Test t2 = new Test(10);
PrintX();
}

static void PrintX()
{
Console.WriteLi ne(x);
}
}

It won't compile, because the static method doesn't have access to the
instance variable x.

However, suppose you *could* compile it, as it looks like you want to.
What would it print? 5 or 10? What would happen if you hadn't created
any instances at all?

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Vadym Stetsyak]

> Static methods will be in the stack right (or is it?).

What does it mean "Static methods will be in the stack"?
Static methods can be accessed only through the type (e.g. class) if you
will pass instance variable as parameter to static method - that's okay, you
will be able to use them (only with public modifier)

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

If that is the case, why is it being said that static methods can't access instance variables?

You are confusing two differents things, it has nothing to do with where
the variables are kept, static methods cannot access instance variables for
different reasons, a call to a static method is done from a class
perspective, Class.StaticMet hod() you don't need to have an instance to
call it, therefore you cannot use a variable that is dependand of an
instance to exist.

Static methods will be in the stack right (or is it?). And the instance pointers will be in the stack too.
No, in the stack you will never find code, the code is kept somewhere else,
the stack is only used to temporary placement of local variables and to keep
a pointer to where return the execution when the method finish the
execution.
So isn't it possible for static methods to 'indirectly' access instance

variables through the instace pointers in the stack?

Why are you assuming that an instance exist?
Maybe an example is good here, take the Math class of the framework, you
NEVER create an instance of it, but you use its static methods.
If you need to have access to instance variables you can do so by passing
it as a parameter:

class A{
private int i;
static int m( A a)
{
a.i = a.i *2;
return a.i;
}
}
As you see you have access to the private members of the instance. Is this
what you are trying to do?
Hope this help,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation

[Rakesh]

I am extremely sorry to have been vague in describing my issue. I am not thinking in the OOPS perpective, I am thinking in the internal compiler perpective

Dataset ds = new Dataset()
static DataSet sds = new Dataset()
static int x = 0

From what I understand, the pointer ds is stored in the stack, and the object new Dataset() is allocated in the heap. Also, pointer sds is in the stack, but where is this object allocatd? - heap or data area? Where is the associated class being allocated

I am just curious on how exaclty things are done by the compiler

Thanks a lot

Rakes

[Jon Skeet [C# MVP]]

Rakesh <an*******@disc ussions.microso ft.com> wrote:

I am extremely sorry to have been vague in describing my issue. I am
not thinking in the OOPS perpective, I am thinking in the internal
compiler perpective.

Dataset ds = new Dataset();
static DataSet sds = new Dataset();
static int x = 0;

From what I understand, the pointer ds is stored in the stack, and
the object new Dataset() is allocated in the heap.

That depends on where that code is. You've given a snippet without any
context. Given that you've got the "static" modifier, I'll assume that
ds is an instance variable - in which case, no, it's not on the stack,
it's on the heap (as are the other two).

As I said before, see http://www.pobox.com/~skeet/csharp/memory.html
for a more detailed explanation.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too