Hi Kevin,
My project is throwing an occasional "unhandled win32 exception" error and I've been trying to figure out why. There is no consistency in the timing so I assume that I have a dangling pointer somewhere.
I doubt you're on the right track with changing standard pointers to
ref_ptrs in function arguments, but when unsure it's better to use
ref_ptrs everywhere.
The "right way" to debug your error would be to compile a debug version
and run your code in a debugger. Then the debugger would likely tell you
exactly which pointer was left dangling, you'd have a stack trace, and
it would be relatively easy to track down the cause. Just sprinkling
ref_ptrs everywhere in the hope that it'll fix it is not a solution, IMHO.
But to answer your more concrete question:
Is there an equivalant means of casting an osg::ref_ptr<osg::node> into an
osg::ref_ptr<osg::MatrixTransform> when using referenced object pointers? I'm trying
to do something like:
--- snip ---
void operator()( osg::ref_ptr<osg::Node> node, osg::ref_ptr<osg::NodeVisitor>
nv )
{
osg::ref_ptr<osg::MatrixTransform> MatrixXform =
dynamic_cast<osg::ref_ptr<osg::MatrixTransform>(node) ;
if ( MatrixXform )
--- snip ---
osg::ref_ptr<osg::MatrixTransform> MatrixXform =
dynamic_cast<osg::MatrixTransform*>(node.get());
A ref_ptr is an object on the stack (not a pointer) that tracks a
pointer. And ref_ptr::get() returns a raw pointer to the underlying
object. So you can construct (or here, assign to) a ref_ptr from a raw
pointer.
So from right to left:
1. You extract the raw Node* pointer from a ref_ptr<Node>
2. You dynamic_cast that to a MatrixTransform*
3. You assign that to a ref_ptr<MatrixTransform>
4. Bob is your uncle.
Note that in the process, the ref count of node will be incremented if
it was really a MatrixTransform (i.e. if the assignment assigned
something other than NULL), so your function will have 2 refs (one in
the temporary ref_ptr<Node>, and one in the ref_ptr<MatrixTransform>).
This is unnecessary, as the temporary ref_ptr<Node> in the function
arguments guarantees that the object will not be deleted in the scope of
the function. So you could do this instead:
osg::MatrixTransform* MatrixXform =
dynamic_cast<osg::MatrixTransform*>(node.get());
As I said, storing it in a raw pointer is safe at that point because of
the temporary ref_ptr<Node> in the function arguments which will be
destroyed when the function ends.
So you see, ref_ptrs require a bit of work wrapping your mind around
them, but it's not magic and it all works really well.
Hope this helps,
J-S
--
______________________________________________________
Jean-Sebastien Guay [email protected]
http://www.cm-labs.com/
http://whitestar02.webhop.org/
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