RFR (S) JDK-8223017: [lworld] checkcast/instance broken for LW2 arrays

[David Simms]

Nice spotting, I didn't differentiate the "checkcast" behavior for 
"Q-type descriptors" and "Array Q-type descriptors".

Since we are heading into a local holiday (tonight and tomorrow, bonfire 
night), I'll leave a note on my thinking here if I don't get to it until 
Thursday...

      * I probably need to || in another bit for arrays of q-type in the
        constant pool tag for the difference in behavior. Thinking of
        using "JVM_CONSTANT_Unicode" since it is unused (further mess,
        but there are not separate bits left)
      * anewarray and multianewarray needs something to tell them it's a
        q-type array, but for the interpreter at least we jump into the
        VM...so I wonder if we need the constant tag encoding at all

Will look a little further into this...

Cheers

/D


On 30/04/19 12:27 PM, Tobias Hartmann wrote:
> Hi Mr. Simms,
>
> I'm seeing the following inconsistent behavior:
>
>    MyValue1?[] va1 = (MyValue1?[])null;  // does not throw NPE
>    MyValue1?[] va2 = null;               // does not throw NPE
>    MyValue1[]  va3 = null;               // does not throw NPE
>    MyValue1[]  va4 = (MyValue1[])null;   // throws NPE
>
> Thanks,
> Tobias
>
> On 29.04.19 12:01, David Simms wrote:
>> Here's a fix for the missing super type relationship for null-free arrays, i.e. "[QFoo;" <:
>> "[LFoo;"...once LW2 array support went in, it accidentally skipped it's null-allow type and went
>> straight to Object[]...added a few more test cases.
>>
>> Webrev:
>>
>> http://cr.openjdk.java.net/~dsimms/valhalla/8223017/
>>
>> Bug:
>>
>> https://bugs.openjdk.java.net/browse/JDK-8223017
>>