Re: [patch] Don't crash on stepping "bad frame"

[Andrew Cagney <cagney at redhat dot com>]

Mark,

Interesting work-around; I'll add some comments to explain exactly 
where/when this senario occures.  And where/when it doesn't.  For 
instance a step-out through a sigalt stack, whith a bad unwind, will 
make the wrong decision.

Andrew

Mark Wielaard wrote:
> Hi,
>
> While working on #5259 I noticed that the stepping engine crashes and
> burns on x86_64 when a bad frame without unwind info is being stepped
> into. This patch handles that case gracefully. And you can now safely
> next through simple examples programs like funit-hello as we did in the
> last demo - you can still drop into the wrong frame till #5259 is fixed
> though.
>
> frysk-core/frysk/stepping/ChangeLog
> 2008-02-29  Mark Wielaard  <mwielaard@redhat.com>
>
>     * StepOverTestState.java (handleUpdate): Don't crash when there is
>     a bad outer frame.
>
> Committed,
>
> Mark
>
> --- a/frysk-core/frysk/stepping/StepOverTestState.java
> +++ b/frysk-core/frysk/stepping/StepOverTestState.java
> @@ -86,6 +86,16 @@ public class StepOverTestState extends State {
>                  * it exits - success!
>                  */
>                 Frame frame = newFrame.getOuter();
> +               if (frame == null)
> +                 {
> +                   // But urgh... Where did our outer frame go...
> +                   // We need to just try to keep stepping till we are
> +                   // able to get a solid frame again.
> +                   tse.getSteppingEngine().continueForStepping(this.task,
> +                                                               true);
> +                   return this;
> +                 }
> +
>                 tse.getSteppingEngine().setBreakpoint(this.task,
>                         frame.getAddress());
>                 return new StepOverState(this.task);
>
>
>