[vbox-dev] crash when restoring a snapshot

Klaus Espenlaub klaus.espenlaub at oracle.com
Fri Jul 30 09:14:53 PDT 2010

On 30.07.2010 17:31, Huihong Luo wrote:
> if the debugger says it's NULL, it must be so, perhaps some overlooks?
> This is the first time I ever got this crash.
> What I did is very simple, create a new vm (XP Mode vm this case,
> shouldn't matter), boot it, take a snapshot, boot vm again, then
> immediately power if off, now try to restore the snapshot, and got that
> error.

Of course I believe that you hit a case where it was indeed NULL. 
However that doesn't give a hint what the root cause of the bug is. I'm 
not going to add a NULL check before the crashing line and blindly skip 
it without knowing WHAT is going wrong and WHY.

> I am trying to recompile the latest svn code right now to double check this

Much appreciated, as the fact that this line caused a crash simply isn't 
providing enough information to do a proper fix. Tested restoring 
snapshots with a couple of VMs, and it worked.


> --- On *Fri, 7/30/10, Klaus Espenlaub /<klaus.espenlaub at oracle.com>/* wrote:
>     From: Klaus Espenlaub <klaus.espenlaub at oracle.com>
>     Subject: Re: [vbox-dev] crash when restoring a snapshot
>     To: vbox-dev at virtualbox.org
>     Date: Friday, July 30, 2010, 7:16 AM
>     On 30.07.2010 05:18, Huihong Luo wrote:
>      > seems that in this function: mMediaData.backedUpData() might be NULL
>     Do you have a reproduction scenario? Without one it's nearly
>     impossible to find this bug. The call trace below provides no
>     information which would give hints what could lead to this. We don't
>     fix bugs by inserting a check based on the fact that the pointer was
>     NULL. The cause needs to be investigated, as the pointer must not be
>     NULL by design in this place.
>     Klaus

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