Re: [Gnash-commit] /srv/bzr/gnash/avm2 r9685: Fix segfault caused by null objects in the scope stack.

[strk]

On Mon, Nov 17, 2008 at 04:09:52PM +0800, Tom Stellard wrote:
> On Mon, Nov 17, 2008 at 1:15 AM, strk <address@hidden> wrote:
> > As for the as_error, wrap it always in IF_VERBOSE_ASCODING_ERRORS
> > so any error can also be disabled at compile time.
> > Still, you don't want to abort if user passes a NULL property,
> > so you'd do something like:
> >
> >
> >        prop = getProperty();
> >        if ( !prop )
> >        {
> >                IF_VERBOSE_ASCODING_ERRORS(
> >                log_aserror(_("..."), ...);
> >                );
> >                return;
> >        }
> >        pushStack(prop);
> >
> > --strk;
> >
> >
> 
> In this case, if the property is null then nothing is pushed onto the
> stack, this could cause some problems with the following opcodes.
> Anytime AVM2 tries to manipulate the stack it will think there are
> more items on the stack than there actually are.  This will cause
> other opcodes to fail in ways that might not be so clear.  Is this OK?

Probably not, still push something on the stack if you're expected to.
Undefined most likely.

>  Is the current expectation that after an actionscript error the movie
> behavior is undefined?

Well, yes. But it's still worth keeping the stack as much close to
the expected one that possible,so further error messages would
be cleaner.

--strk;