When to add __gc decorator

[TT (Tom Tempelaere)]

Hey everyone,

If I am writing a .NET library using managed C++, when exactly do I have to
decorate a pointer with the __gc decorator?

Thanks,
--
Tom Tempelaere.

[William DePalo [MVP VC++]]

"TT (Tom Tempelaere)" <_|\|_0$P@|/\|titi____AThotmailD.Tcom|/\|@P$0_|\|_>
wrote in message news:DB**********************************@microsof t.com...

If I am writing a .NET library using managed C++, when exactly do I have
to
decorate a pointer with the __gc decorator?

Well, pointers to managed objects are always __gc. So mostly, you don't have
to be explicit where you point to managed objects though it doesn't hurt.

Suppose though, that you have a managed class and that that managed class
has a member which has an unmanaged type - say integer. If you needed a
pointer to that integer then you'd need to mark the pointer as __gc. That's
because that ordinary integer is set on the managed heap and it can move out
from under you.

I hope this helps. I had hoped to come up with a more definitive, less
annecdotal explanation for you. I scanned the book "Essential Guide to
Managed Extensions for C++" hoping to find some advice from on high that I
could quote. What there is in the book is a whole _chapter_ on the topic.
I'd recommend the book, but depending on your release schedule, you might
want to wait for a book on C++/CLI which supplants MC++ in VS.Net 2005

Regards,
Will

[TT (Tom Tempelaere)]

Thank you William, I understand now.

Tom Tempelaere.

[ismailp]

you may need to use __gc on managed arrays, too.

i'd also recommend the same thing; wait for C++/CLI. you can get its
beta1 or latest ctp and enjoy using new language. there is no __gc in
C++/CLI.

[_B]

On Tue, 8 Mar 2005 11:03:51 -0500, "William DePalo [MVP VC++]"
<wi***********@mvps.org> wrote:

.... depending on your release schedule, you might
want to wait for a book on C++/CLI which supplants MC++ in VS.Net 2005

Regards,
Will

I had just posted a query about books on C++/CLI. Looks like you just
answered it. I'm surprised that no one got the jump on the 2005
compiler release.

Well, in the absence of a book, are there any good web-based
references on the subject?

[William DePalo [MVP VC++]]

"_B" <[e-mail]> wrote in message
news:gt********************************@4ax.com...

On Tue, 8 Mar 2005 11:03:51 -0500, "William DePalo [MVP VC++]"
I had just posted a query about books on C++/CLI. Looks like you just
answered it. I'm surprised that no one got the jump on the 2005
compiler release.

Well, in the absence of a book, are there any good web-based
references on the subject?

This is an introduction:

http://msdn.microsoft.com/msdnmag/is...C/default.aspx

This details the differences between MC++ and C++/CLI:

http://msdn.microsoft.com/library/de...TransGuide.asp

They should get you started. You can try googling for more, perhaps
searching for articles written by Lippman or ones on "C++/CLI"

Regards,
Will