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RE: [cdt-dev] Disassembly view throws NPE when debugging with CDI
Andy, I'm going to investigate this some more and will hopefully have a plan of action. Technically, one could say any method that returns a reference could theoretically (some day, some way) return null. Should every such call have a null pointer check after it? I'll side-step that mine field for now and just say I'll keep working on this to get this resolved :-) 

John

At 12:04 PM 6/17/2010, Andy Jin wrote:

Hi, John,

Thanks for the reply. I agree that this looks strange and I only can
re-produce it with this special program linking a large shared library.
I can't re-produce it with a simply "Hello World" so I agree this is
some race condition here.

The disassembly view still shows correct content after the program is
stopped (threads are suspended).

It's not easy to debug this because if I stop at a breakpoint I am not
fast enough to capture the states of the thread before it is refreshed.
But I see it always happens at thread number 1 which (I believe) it's
still at the running mode.

After all, when we call a function which threaten to return NULL
shouldn't we at least check for it?

Thanks,
Andy

-----Original Message-----
From: cdt-dev-bounces@xxxxxxxxxxx [mailto:cdt-dev-bounces@xxxxxxxxxxx]
On Behalf Of John Cortell
Sent: June 17, 2010 12:17 PM
To: CDT General developers list.; cdt-dev@xxxxxxxxxxx
Subject: Re: [cdt-dev] Disassembly view throws NPE when debugging with
CDI

Andy,

Something strange is going on. Notice that the code to get the top
stack frame only executes if the new context is a stack frame. So,
how is it that we are being given a stack frame as the new context
but that frame's thread isn't suspended?

On the surface, it looks like a bug somewhere else--a race condition
or some incoherent state. If you could figure out a way to rig the
CDT code to duplicate what's happening for you, and provide that as a
patch, that would allow us to reproduce it and investigate further.

John

At 10:54 AM 6/17/2010, Andy Jin wrote:
>When debugging a program with a large share library linked over a
remote
>target, the program takes some time to be load the share library.
During
>this loading period if I have the Disassembly view opened it will throw
>NPE with below trace:
>
>java.lang.NullPointerException
>at
>org.eclipse.cdt.debug.internal.ui.disassembly.dsf.DisassemblyBackendCdi
.setDebugContext(DisassemblyBackendCdi.java:132)
>at
>org.eclipse.cdt.dsf.debug.internal.ui.disassembly.DisassemblyPart.updat
eDebugContext(DisassemblyPart.java:1798)
>at org.eclipse.cdt.dsf.debug.internal.ui.disassembly.DisassemblyView
>$1.selectionChanged(DisassemblyView.java:66)
>at org.eclipse.ui.internal.AbstractPartSelectionTracker
>$1.run(AbstractPartSelectionTracker.java:119)
>at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
>at org.eclipse.core.runtime.Platform.run(Platform.java:888)
>at
>org.eclipse.ui.internal.AbstractPartSelectionTracker.fireSelection(Abst
ractPartSelectionTracker.java:117)
>at org.eclipse.ui.internal.PagePartSelectionTracker
>$1.selectionChanged(PagePartSelectionTracker.java:49)
>......................................
>
>Looking at
>org.eclipse.cdt.debug.internal.ui.disassembly.dsf.DisassemblyBackendCdi
.setDebugContext(DisassemblyBackendCdi.java:132),
>it does a "fTargetContext.getTopStackFrame()". This function can
>return Null if the thread is not in suspended mode thus the stack
>frame is an empty list.
>
>In our case the program is in the process of loading the share library
>so its thread is not suspended.
>
>It's pretty re-producible with CDI. I haven't seen this problem with
>DSF.
>
>Is it simply a miss to check for Null condition or is it something
>deeper in the code?
>
>Thanks,
>Andy
>_______________________________________________
>cdt-dev mailing list
>cdt-dev@xxxxxxxxxxx
>https://dev.eclipse.org/mailman/listinfo/cdt-dev


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