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

[Coleen Phillimore]

This change looks good.  Thank you for fixing it.
Coleen

On 10/10/2012 12:44 PM, serguei.spitsyn at oracle.com wrote:
> Hi Jiangli,
>
>
> On 10/10/12 9:37 AM, Jiangli Zhou wrote:
>> Hi Serguei,
>>
>> Thanks for the review! Please see comments below.
>>
>> On 10/09/2012 06:05 PM, 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.
>>> 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);
>>> assert(java_lang_String::is_instance(entry));
>>>
>>> In this case, a reference from CP to string is reported regardless 
>>> it is pseudo string or not.
>>
>> Those are very good questions. Here is an example of the specific 
>> case with a generated JSR292 java.lang.invoke.LambdaForm$MH class. 
>> The follow are two constant pool entries of the class. Entry 16 is a 
>> "sun/misc/Unsafe" String, which could be patched using a 
>> sun.misc.Unsafe klass oop.
>>
>>         ...
>>         (0016) tag=Utf8 "sun/misc/Unsafe"
>>         (0017) tag=Class "sun/misc/Unsafe"
>>         ...
>>
>> I discussed with John Rose about different ways to fix the assertion 
>> issue. The code you have above uses pseudo_string_at() to access the 
>> 'entry', which is similar to one of the version we discussed. The 
>> current change was chosen as it's the simplest solution.
>
> I'm Ok with the simplest solution.
>
> Thank you for the details!
> -Serguei
>
>>
>> Thanks,
>>
>> Jiangli
>>>
>>>
>>> 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
>>>
>>
>