Access violation on Graph.CoCreateInstance   

Hi,

I have player application which first initialize all filters add to graph 
and go to run mode. That goes well. Than when i press stop it goes to stop 
mode and release all filters, mediaevent, mediacontrol and graph (in that 
order). Now when i call play again i get access violation on:

hr = pGraph.CoCreateInstance(CLSID_FilterGraph);

What is causing this ?

    Thanx

date: Fri, 19 Sep 2008 12:00:57 +0200   author:   Gossamer

Re: Access violation on Graph.CoCreateInstance   

Hi,

> hr = pGraph.CoCreateInstance(CLSID_FilterGraph);
>
> What is causing this ?

If you have an access violation, you should also have a call stack at
exact access violation position. It would be helpful if you pasted it
into the topic.

If you really have the problem on this line, I'd suspect you still
have a non-NULL value in pGraph variable (what is the type?
CComPtr<IGraphBuilder> ?) but the actual object behind the pointer was
already destroyed.

Roman

date: Fri, 19 Sep 2008 04:45:18 -0700 (PDT)   author:   Roman Ryl...

Re: Access violation on Graph.CoCreateInstance   

"Roman Ryl..."  wrote in message 
news:c57fbefd-3d4d-40cc-9fb7-eeffb62cf14b@8g2000hse.googlegroups.com...
> Hi,
>
>> hr = pGraph.CoCreateInstance(CLSID_FilterGraph);
>>
>> What is causing this ?
>
> If you have an access violation, you should also have a call stack at
> exact access violation position. It would be helpful if you pasted it
> into the topic.
>
> If you really have the problem on this line, I'd suspect you still
> have a non-NULL value in pGraph variable (what is the type?
> CComPtr<IGraphBuilder> ?) but the actual object behind the pointer was
> already destroyed.
>

It is CComPtr<IGraphBuilder>. The value of pGraph is 0 before call. Before 
CoCreate i use pGraph.Release() so the object is destroyed.
also there are those two interfaces derived from pGraph
hr = pGraph->QueryInterface(IID_IMediaControl, (void **)&pControl);
hr = pGraph->QueryInterface(IID_IMediaEvent, (void **)&pEvent);
which i also Release before reinitialize pGraph.

> Roman

date: Fri, 19 Sep 2008 14:09:33 +0200   author:   Gossamer

Re: Access violation on Graph.CoCreateInstance   

On Sep 19, 2:09 pm, "Gossamer"  wrote:
> "Roman Ryl..."  wrote in message
>
> news:c57fbefd-3d4d-40cc-9fb7-eeffb62cf14b@8g2000hse.googlegroups.com...
>
> > Hi,
>
> >> hr = pGraph.CoCreateInstance(CLSID_FilterGraph);
>
> >> What is causing this ?
>
> > If you have an access violation, you should also have a call stack at
> > exact access violation position. It would be helpful if you pasted it
> > into the topic.
>
> > If you really have the problem on this line, I'd suspect you still
> > have a non-NULL value in pGraph variable (what is the type?
> > CComPtr<IGraphBuilder> ?) but the actual object behind the pointer was
> > already destroyed.
>
> It is CComPtr<IGraphBuilder>. The value of pGraph is 0 before call. Before
> CoCreate i use pGraph.Release() so the object is destroyed.
> also there are those two interfaces derived from pGraph
> hr = pGraph->QueryInterface(IID_IMediaControl, (void **)&pControl);
> hr = pGraph->QueryInterface(IID_IMediaEvent, (void **)&pEvent);
> which i also Release before reinitialize pGraph.
>
>
>
> > Roman- Hide quoted text -
>
> - Show quoted text -

You are using smart pointers, so you should not free the objects using
Release(). And also, why don't you keep your graph and reuse it?

date: Fri, 19 Sep 2008 06:31:06 -0700 (PDT)   author:   Michel Roujansky - Senior developer, Starfish Technologies Ltd

Re: Access violation on Graph.CoCreateInstance   

Hi,

> You are using smart pointers, so you should not free the objects using
> Release(). And also, why don't you keep your graph and reuse it?

CComPtr::Release is safe to call (unlike CComPtr::p->Release you might
have thought of). And CoCreateInstance assumes current value of member
pointer p is NULL, so Release before CoCreateInstance is safe and
basically required if the variable is re-creating a pointer.

Roman

date: Fri, 19 Sep 2008 07:13:19 -0700 (PDT)   author:   Roman Ryl...

Re: Access violation on Graph.CoCreateInstance   

"Michel Roujansky - Senior developer, Starfish Technologies Ltd"
 wrote:
>
>You are using smart pointers, so you should not free the objects using
>Release().

If you want to create a new object with the same smart pointer, you MUST
call Release (or set it to 0).  CComPtr::QueryInterface will assert if the
pointer it contains is not NULL.
-- 
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.

date: Sat, 20 Sep 2008 21:14:32 -0700   author:   Tim Roberts