Error: Bad reference counting?

Guest · Post by **Guest** » Sat Oct 01, 2005 2:41 am

I'm trying to use my own linked list class to manage objects in Irrlicht. The actual error message I get is an access violation error but it points me to an Irrlich header. A comment there claims I'm doing bad reference counting? I don't even know what that is. My linked list code is sound, I've used it before. Is there something I have to do when dynamically allocating nodes in Irrlicht? The error seems to occur only if I drop the nodes I create?

CZestmyr · Post by **CZestmyr** » Sat Oct 01, 2005 6:22 pm

I think that you shouldn't drop() them before calling grab() on them in your list, which takes care of them. Calling drop() on them before any other class called grab() causes them to cease to exist, which causes problems, when you try to access their formal memory location.

Guest · Post by **Guest** » Mon Oct 03, 2005 2:13 am

I've never used grab(), do I call it when I create the node or just before I drop it? What does grab actually do for Irrlicht?

Thanks for the help, I'll try it and post back if I have any problems.

Spintz · Post by **Spintz** » Mon Oct 03, 2005 5:45 am

I recommend looking at the documentation for ISceneManager and notice the difference between calls with add and create in their names, and what it says about drop().

The basic rule is : create functions don't grab() the object, add functions do.

So, If you call :

Code: Select all

anim = createXXXAnimator(...);

after a successful return from the function, the ref count of the animator is 1. Now, when you call

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node->addAnimator(anim);

This function for a node, will associate the animator with the node, and since the node relies on the animator's data, it will call grab() on the animator. So now, after a successful return from this function the animator's reference count is 2. If you no longer need the animator for anything else, you call drop() on it, so that when the sceneNode is done, and it calls drop on the animator( which it will, since it grabbed it ), the animtor will be destroyed and you don't have to worry about it.

There's tons of documentation about all of this. Look at IUnknown and ISceneManager.

pfo · Post by **pfo** » Mon Oct 03, 2005 6:15 am

Out of curiousity, are you using memcpy on a struct with core::string? That was giving me a problem, when the first string frees it de-allocates the memory, when the copied string tries to free itself it tries to delete the same memory, causing the same problem you have.

Guest · Post by **Guest** » Mon Oct 03, 2005 5:30 pm

don't grab() the object, add functions do

Yes it's true, but as far as I have understood, he wants to make some sort of his own scene manager.

Guest · Post by **Guest** » Tue Oct 04, 2005 11:44 am

So if I create an object using add, I just have to call:

SceneNode = smgr->addBillboardSceneNode(0, core::dimens...
...
SceneNode->remove();

to get rid of it and clean up all the memory it used?