Review request: 8000459: assert(java_lang_String::is_instance(entry)) failure with various mlvm tests

[David Holmes]

On 10/10/2012 11:05 AM, serguei.spitsyn at oracle.com wrote:
> Hi Jiangli,
>
> I'm not very familiar with the pseudo strings, and so, just have a
> question:
>
> *src/share/vm/prims/jvmtiTagMap.cpp*
>
> 2927 entry = pool->resolved_string_at(i);
> 2928 assert(java_lang_String::is_instance(entry) ||
> 2929 pool->is_pseudo_string_at(i), "must be string");
>
> I have a little of doubt the above is correct.
>
> What value the "entry" will have in a case of pseudo string cp entry?
> Just want to understand what constant pool reference will be reported.

The pool stores strings and pseudo-strings in the same way. So 
pool->resolved_string_at(i) and pool->pseudo_string_at(i, 
cp_to_object_index(i)) return the same thing.

So entry is either a real string or a pseudo-string - hence the assert 
checks for either one.

There were a number of ways this code could have been modified to handle 
this, but augmenting the assert was simplest.

> Do you see all related failing tests passed?
>
> Would something like the following be more accurate ?
> entry = pool->is_pseudo_string_at(i) ?
> pool->pseudo_string_at(i, cp_to_object_index(i)) :
> pool->resolved_string_at(i);

entry is the same no matter which path is taken.

> assert(java_lang_String::is_instance(entry));

That assert fails if entry was a pseudo-string.

David
-----

> In this case, a reference from CP to string is reported regardless it is
> pseudo string or not.
>
>
> Thanks,
> Serguei
>
> On 10/9/12 4:26 PM, Jiangli Zhou wrote:
>> Please review following fix for 8000459:
>>
>> http://cr.openjdk.java.net/~jiangli/8000459/webrev/
>>
>> With JSR292, a constant pool String entry could be patched to a
>> non-string oop. The assert in
>> VM_HeapWalkOperation::iterate_over_class() needs to be adjusted to
>> reflect that.
>>
>> Thanks,
>>
>> Jiangli
>