Review Request JDK-8193325: StackFrameInfo::getByteCodeIndex returns wrong value if bci > 32767

[mandy chung]

On 12/12/17 5:29 PM, John Rose wrote:
> On Dec 12, 2017, at 5:24 PM, David Holmes <david.holmes at oracle.com 
> <mailto:david.holmes at oracle.com>> wrote:
>>
>> as per getByteCodeIndex() it needs to be able to store "-1" to 
>> indicate no-bci?
>
> Yes, that's the essential requirement, to encode a "none" value.
>
> FWIW, one natural way to do that here would be to make the int field
> @Stable and have the accessor return one less than the stored field value.
>
> Then, by the rules of @Stable, the field starts out at the logical value
> of -1, and can transition to a valid BCI if patched to a non-zero value
> in the range 1..(2^16).
>

Thanks for suggesting @Stable that would help this case.  I can't 
understand why the field has to be patched with non-zero value.  Is this 
something special requirement for @Stable?

> Making it "final" and initialized to -1 is not too terrible either, 
> although
> that creates some tech. debt we need to discharge when upgrading
> finals to be trustable.

Mandy
[1] 
http://cr.openjdk.java.net/~bchristi/8185925/StackFrameInfo.jol.rmDeclClass.txt