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From Gregory Shimansky <gshiman...@apache.org>
Subject Re: [launcher] Uncaught exceptions not printed on J9 VME
Date Sun, 14 Oct 2007 16:57:17 GMT
Oliver Deakin wrote:
> Hi all,
> A little while back there was a thread called "[drlvm] Should the 
> launcher print uncaught exceptions?" [1] where we discussed the fact 
> that running a test case like [2] did not print a stack trace with the 
> Harmony launcher. As part of this discussion, HARMONY-1819 was raised 
> and the line "(*jvm)->DetachCurrentThread(jvm)" was added to the 
> launcher main.c in repo revision r464443.
> HARMONY-3713 was later raised pointing out that calling 
> DetachCurrentThread() to detach the main thread was contrary to the spec 
> [3], and the line was removed from main.c. However, I have just noticed 
> that if you run [2] on the current J9 VME (and, in fact, on the RI with 
> a simple launcher) you do not get any stack trace printed, and I imagine 
> this has been the case since the commit of HARMONY-3713.
> The RI has a bug [4], contrary to the spec [3], which requires 
> DetachCurrentThread() to be called by the invoking launcher if you wish 
> to see the stack trace of an uncaught exception. It appears that J9 has 
> matched this bug, probably so no unexpected trace is printed in 
> launchers programmed against the RI.
> So currently running Harmony classlib with the J9 VME will not result in 
> any stack trace being printed for uncaught exceptions, which makes 
> debugging issues where that occurs more troublesome. Id like to propose 
> that the DetachCurrentThread() line be readded to main.c (i.e. the 
> opposite of the patch for HARMONY-3713), perhaps with a comment to show 
> that this is to match the behaviour of the RI rather than the spec.
> Any objections?

I wonder if simply adding

if ((*env)->ExceptionCheck(env))

is enough to print out stack trace in the main thread without violating 
the spec.


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