struct on the stack... sometimes on the heap?

[Johndoe]

Hi,

A struct lives on the stack, right? What happens if I create a struct that
contains a reference type?

I'm guessing that there will be a pointer on the stack refering to my
reference type. I'm not 100% sure. Can someone please confirm?

Thanks.

[Marc Gravell]

As I understand it...

A struct lives on the stack, right?

As a variable, yes; as a field in a class, no - it goes on the heap as
part of the object

What happens if I create a struct that
contains a reference type?

A struct (or indeed a class) never "contains" (in terms of memory
layout) a reference type; it contains (as you say later) a reference
(essentially an integeric field) to the reference tpe (which always
lives on the heap in managed code). Contrast that the other way around;
a class (or indeed a struct) with a struct field actually has a block
of memory (in it's own definition) reserved for the contained struct
(this doesn't hold true for arrays, which are referenced).

I'm guessing that there will be a pointer on the stack refering to my
reference type.

(key word: stack) - or heap, depending. But essentially you have it
correct.

Marc

[Carl Daniel [VC++ MVP]]

Johndoe wrote:

Hi,

A struct lives on the stack, right? What happens if I create a struct
that contains a reference type?

I'm guessing that there will be a pointer on the stack refering to my
reference type. I'm not 100% sure. Can someone please confirm?

Exactly.

If you create a reference type that contains a struct, then you'll get a
struct on the heap. Anything that results in boxing (e.g. converting to
object, calling a virtual function, etc) will also result in a struct on the
heap.

-cd

[Jon Skeet [C# MVP]]

Johndoe <jo*****@johndo e.comwrote:

A struct lives on the stack, right?

Not always. A struct which is part of a reference type will be on the
heap. The data for the struct lives wherever the variable lives,
basically. See http://www.pobox.com/~skeet/csharp/memory.html

What happens if I create a struct that
contains a reference type?

I'm guessing that there will be a pointer on the stack refering to my
reference type. I'm not 100% sure. Can someone please confirm?

That's correct. Note that the referenced *object* isn't really part of
the struct - only the reference is.

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

[simida]

Yes, a reference that stored in the struct just like 32BIT INT value.
the reference value maybe contain a referenced *object* 32 BIT address
that located in the heap. Of course, it is a simple explanation.

(Maybe Like Handler?)
Jon 写�：

Johndoe <jo*****@johndo e.comwrote:

A struct lives on the stack, right?

Not always. A struct which is part of a reference type will be on the
heap. The data for the struct lives wherever the variable lives,
basically. See http://www.pobox.com/~skeet/csharp/memory.html

What happens if I create a struct that
contains a reference type?

I'm guessing that there will be a pointer on the stack refering to my
reference type. I'm not 100% sure. Can someone please confirm?

That's correct. Note that the referenced *object* isn't really part of
the struct - only the reference is.

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

[Barry Kelly]

"simida" <yo**********@g mail.comwrote:

Yes, a reference that stored in the struct just like 32BIT INT value.
the reference value maybe contain a referenced *object* 32 BIT address
that located in the heap. Of course, it is a simple explanation.

A reference value stored anywhere is a pointer (of size IntPtr.Size -
changes between 32 / 64 etc. versions of the runtime) to an object on
the heap. The reference value is only and exactly that, a pointer (i.e.
an address) to the heap, nothing more.

-- Barry

--
http://barrkel.blogspot.com/