review for 7055355: JSR 292: crash while throwing WrongMethodTypeException

[Tom Rodriguez]

On Jun 16, 2011, at 1:56 PM, John Rose wrote:

> On Jun 16, 2011, at 10:18 AM, Tom Rodriguez wrote:
> 
>> I increased the slop value in my last set of changes and we're currently not failing this test that I can see.  I agree that the test is slightly mystifying and wouldn't mind removing it.
> 
> I would prefer to keep it for the following reason:
> 
> When control returns to a RF, the SP is restored to a saved value.  Comparing it to the saved argument base is a reasonable thing, since the RF is known to contain only (a) up to 255 saved arguements, and (b) a a few words of fixed overhead.  If the restored SP is bad, and/or if the saved argument base is bad, we can detect this quickly using the comparison before the corruption goes further.
> 
> The slop has to be large enough to contain the "save_frame" size used by the RF.

I agree in theory but the only thing it's done so far is report false positives.  The old slop value was kind of in agreement with the save_frame size but I had to raise it to 45 to get it to shut up, with no apparent ill effects.  My last push raised it to 35.  After Christian's comments I decided to disabled it in my push since I think it's well intentioned but wrong.

tom

> 
> -- John