gamedevlists-windows

[GD-Windows] new/delete across DLL's

[Ben H. <cr...@ca...>]

Am I doing something wrong, or is this correct behaviour:

in core.dll I have a class CFooBar.

in the game exe, I call wibble =3D new CFooBar;
Later on, within the exe, I call delete wibble; and get an Assert=
 warning because I'm deallocating from the wrong heap.

This seems very strange, that I can only deallocate a class=
 defined in a DLL from within that DLL, even if the instance was=
 allocated somewhere else. Am I understanding this correctly, or=
 am I doing something else to cause the problem? Is there any way=
 round this?

[ cruise / casual-tempest.net / transference.org ]

RE: [GD-Windows] new/delete across DLL's

[Jon W. <hp...@mi...>]

Welcome to DLL hell.

There are two kinds of DLL hell: the Unix hell, where some library can=20
decide to replace malloc() in the global symbol table, and suddenly=20
you're running with some other allocator than you tested your code=20
with; and the Windows hell, where each DLL can run with its own=20
allocator (say, debug vs release vs version 7.0), which means that you=20
have to balance all allocations and deletions.

The only sane way around this that I've found is to base your cross-
DLL object model on factory functions and abstract interfaces, and use=20
"deleteYourself()" as a virtual function to delete an instance (or go=20
all the way and acquire()/release() with ref counting).

You may note that COM does a lot of these things, btw :-)

Also, for the same reasons, inline functions are often a very bad idea=20
for objects that are supposed to live in DLLs. First, because you have=20
to re-compile the user when you change the implementation of the object=20
(so you can't rev the DLL separately unless you take a LOT of care).=20
Second, because if you happen to allocate memory, then the inline may=20
live in one of many different modules. This is especially bad with STL=20
style containers.

Cheers,

				/ h+



> -----Original Message-----
> From: gam...@li...
> [mailto:gam...@li...]On Behalf Of
> Ben Hawes
> Sent: Monday, March 24, 2003 9:08 AM
> To: gam...@li...
> Subject: [GD-Windows] new/delete across DLL's
>=20
>=20
> Am I doing something wrong, or is this correct behaviour:
>=20
> in core.dll I have a class CFooBar.
>=20
> in the game exe, I call wibble =3D new CFooBar;
> Later on, within the exe, I call delete wibble; and get an Assert=20
> warning because I'm deallocating from the wrong heap.
>=20
> This seems very strange, that I can only deallocate a class=20
> defined in a DLL from within that DLL, even if the instance was=20
> allocated somewhere else. Am I understanding this correctly, or=20
> am I doing something else to cause the problem? Is there any way=20
> round this?
>=20
> [ cruise / casual-tempest.net / transference.org ]
>=20
>=20
>=20
> -------------------------------------------------------
> This sf.net email is sponsored by:ThinkGeek
> Welcome to geek heaven.
> http://thinkgeek.com/sf
> _______________________________________________
> Gamedevlists-windows mailing list
> Gam...@li...
> https://lists.sourceforge.net/lists/listinfo/gamedevlists-windows
> Archives:
> http://sourceforge.net/mailarchive/forum.php?forum_idU5
>=20

Re: [GD-Windows] new/delete across DLL's

[Adrian C. <ce...@ce...>]

Sorry I didn't read all the replies to tis message, I just had to take the
chance that this was already solved.

The way we solved this in OGRE (which is a library that links dynamically)
was to create our own memory manager class (based in the debug version  on
Paul Nettle's *very* *very* nice one) which makes sure that all the calls to
*alloc/free and new/delete are mapped to static member functions of this
memory manager class I told you about later. The end product is that all the
memory gets (de)allocated only in the main DLL's thread.
The side-effect is that you have to include the memory manager's header file
in all the other DLL's as well as in the client application.

My 2c,
Adrian 'cearny' Cearnau

----- Original Message -----
From: "Ben Hawes" <cr...@ca...>
To: <gam...@li...>
Sent: Monday, March 24, 2003 7:07 PM
Subject: [GD-Windows] new/delete across DLL's


Am I doing something wrong, or is this correct behaviour:

in core.dll I have a class CFooBar.

in the game exe, I call wibble = new CFooBar;
Later on, within the exe, I call delete wibble; and get an Assert warning
because I'm deallocating from the wrong heap.

This seems very strange, that I can only deallocate a class defined in a DLL
from within that DLL, even if the instance was allocated somewhere else. Am
I understanding this correctly, or am I doing something else to cause the
problem? Is there any way round this?

[ cruise / casual-tempest.net / transference.org ]



-------------------------------------------------------
This sf.net email is sponsored by:ThinkGeek
Welcome to geek heaven.
http://thinkgeek.com/sf
_______________________________________________
Gamedevlists-windows mailing list
Gam...@li...
https://lists.sourceforge.net/lists/listinfo/gamedevlists-windows
Archives:
http://sourceforge.net/mailarchive/forum.php?forum_idU5