Re: [Flightgear-devel] [PATCH] recent segfaults caused by jsbsim and property tree

[Anders G. <and...@gi...>]

On Thu, 12 Nov 2009, Csaba Halász wrote:

> Hi Everybody!

Hi Csaba!

Good work!

> As you may know we have been recently investigating mysterious
> segfaults experienced with some jsbsim aircraft such as the f16 or the
> hansajet.
> I have identified the following problems:
>
> 1) SGPropertyNode::getNode apparently stops parsing after an index.
> For example, given /foo/bar[0]garbage it happily returns the node
> /foo/bar[0].
> 2) Certain overloads of SGPropertyNode::tie invoke getNode without
> checking the return value.
> 3) FGTurbine::Load is missing a slash in the prefix and so ultimately
> passes garbage to SGPropertyNode::tie.

Did you manage to find out how that happens? I couldn't spot it in 
the code - AFAICS it doesn't happen in JSBSim/standalone and the involved 
JSBSim code ought to be the same.

> 4) The checkTied in FGFDMExec.cpp is assuming property nodes with
> children can not be tied.

That's the one I found and fixed in JSBSim/CVS yesterday :)

> 5) All over jsbsim plain SGPropertyNode objects are cast to FGPropertyManager
>
> Additionally Anders has found some trouble too, I suspect he has
> checked in a fix to jsbsim cvs for that (but I haven't looked).
>
> The primary cause of the trouble is point #3, I have a simple fix
> attached for it as well as for point #4. These are against gitorious
> "next" branch but should be simple enough to apply manually if
> necessary. Even with these checks I get a segfault with the Hansajet.
> During testing, however, that worked as well. I had some other
> modifications that I thought were irrelevant but looks like i was
> wrong. I will re-apply those tomorrow.
>
> Apparently Tim has recently changed the props code, so I'll leave #1
> and #2 for him :)
>
> Finally, point #5 needs some thought.

Yes, indeed.


Cheers,

Anders
-- 
---------------------------------------------------------------------------
Anders Gidenstam
WWW: http://www.gidenstam.org/FlightGear/