[9] RFR (S): Class.getSimpleName() should work for non-JLS compliant class names

Vladimir Ivanov vladimir.x.ivanov at oracle.com
Tue Apr 14 10:59:53 UTC 2015

David, John, thanks for review!

Best regards,
Vladimir Ivanov

On 4/14/15 3:47 AM, David Holmes wrote:
> On 14/04/2015 3:39 AM, Vladimir Ivanov wrote:
>> John, David, thanks for the feedback!
>> What do you think about the following version:
>>    http://cr.openjdk.java.net/~vlivanov/8057919/webrev.02/jdk
>>    http://cr.openjdk.java.net/~vlivanov/8057919/webrev.02/hotspot
> Looks good - thanks.
> David
>> Best regards,
>> Vladimir Ivanov
>> On 4/10/15 10:15 PM, John Rose wrote:
>>> On Apr 9, 2015, at 4:16 PM, David Holmes <david.holmes at oracle.com
>>> <mailto:david.holmes at oracle.com>> wrote:
>>>> Hi Vladimir,
>>>> On 10/04/2015 12:51 AM, Vladimir Ivanov wrote:
>>>>> David, thanks for the feedback!
>>>>> Updated webrev:
>>>>> http://cr.openjdk.java.net/~vlivanov/8057919/webrev.01/jdk
>>>>> http://cr.openjdk.java.net/~vlivanov/8057919/webrev.01/hotspot
>>>>> I restored original logic and call into VM only if it fails.
>>>> This change seems fine to me, but I think John may prefer to see
>>>> getSimpleName implemented such that it always returns the name from
>>>> the innerclass attribute. (Though perhaps with caching if performance
>>>> is a concern?)
>>> Yes, I do prefer the new logic instead of a combination of old and new.
>>> Two concerns:  Somebody somewhere might be relying on a bug in the old
>>> logic and be frustrated by seeing that bug fixed.  This is a fine line
>>> to walk, but in this case I think the behavior change (if any) will show
>>> up in places where we already have outages.  Perhaps someone is
>>> post-processing the result of getSimpleName to correct it.  If so they
>>> may no longer need to do that.
>>> Second, the new logic may itself have issues.  A typical problem with
>>> the InnerClasses attribute is it is broken or stripped, or a related
>>> nestmate is missing.  (See parallel thread in core-libs-dev on 8076264.)
>>>   But the proposed change takes effect after a call to
>>> Class.getEnclosingClass, which uses
>>> InstanceKlass::compute_enclosing_class_impl and accesses the same
>>> InnerClasses record.
>>> This leads me to a comment:  The common code (two uses
>>> of InnerClassesIterator with klass_name_at_matches) should be factored
>>> out.  The factored subroutine should search out the self-record in the
>>> InnerClasses attribute.  The logic is tricky enough that I'm
>>> uncomfortable with it being duplicated.  Key issue:  We don't want to
>>> load any classes doing this lookup.
>>> (For bonus points, factor the third use in that file, the one that looks
>>> not for self but for children-of-self.  Add a boolean flag that varies
>>> the test.)
>>> Bottom line:  The new logic should replace the old.
>>>>>>> The logic to compute simple name (Class.getSimpleName()) for
>>>>>>> inner/nested/local classes is tightly coupled with Java naming
>>>>>>> scheme
>>>>>>> and sometimes fails for classes generated from non-Java code.
>>>>>> Meta-question: if this is non-Java code then what does/should
>>>>>> "simpleName" even mean? "Returns the simple name of the underlying
>>>>>> class
>>>>>> as given in the source code." If there is no (java) source code does
>>>>>> this have any meaning? Should it return "" ?
>>>>> My reading of the JVMS is that InnerClasses attribute can be freely
>>>>> used
>>>>> by non-Java compilers to store simple names for classes they generate.
>>>>> The current wording for inner_name_index doesn't mention Java
>>>>> language.
>>>> True, but it does refer to source code: "represents the original
>>>> simple name of C, as given in the source code from which this class
>>>> file was compiled. " which seems misplaced as we're discussing classes
>>>> for which there is no source code as such.
>>> It could be non-Java source code.  In any case, the indicated component
>>> of the "binary name" of the class is well-defined, whether or not it
>>> occurs in source code.  Note also that classes might be generated by ASM
>>> (no source code per se) but we still have a reasonable expectation of
>>> reflecting on them, even though reflection is (mostly) defined in terms
>>> of source code constructs.
>>>> Anyway it just flags to me that perhaps these Class methods need to be
>>>> generalized a bit given the support for non-Java languages on the JVM.
>>>> But that's for core-libs folk to decide.
>>> Yes, I think that's the issue.  The multi-language folks (like me) would
>>> be disappointed to hear that we decided that non-Java languages don't
>>> have any needs here; they do.
>>> Thanks,
>>> — John
>>>> Thanks,
>>>> David
>>>>> Best regards,
>>>>> Vladimir Ivanov
>>>>>>> Instead of parsing class name and try to extract simple name
>>>>>>> based on
>>>>>>> JLS rules, the fix I propose is to use InnerClasses attribute from
>>>>>>> the
>>>>>>> class file. Simple name is already recorded there.
>>>>>> >
>>>>>>> JVMS-4.7.6: The InnerClasses Attribute
>>>>>>> "inner_name_index: If C is anonymous (JLS §15.9.5), the value of the
>>>>>>> inner_name_index item must be zero. Otherwise, the value of the
>>>>>>> inner_name_index item must be a valid index into the constant_pool
>>>>>>> table, and the entry at that index must be a CONSTANT_Utf8_info
>>>>>>> structure (§4.4.7) that represents the original simple name of C, as
>>>>>>> given in the source code from which this class file was compiled."
>>>>>>> Since I consider backporting the fix into 8u60, I'd like to hear
>>>>>>> opinions about backward compatibility of such change.
>>>>>>> As an alternative solution, I can restore original logic and consult
>>>>>>> InnerClasses attribute when class name parsing logic fails.
>>>>>> I think I'd prefer to see the VM call only used as a fallback if the
>>>>>> regular parsing fails. That would prevent any compatibility issues
>>>>>> for
>>>>>> the 8u backport (ignoring tests that deliberately generate invalidly
>>>>>> named classes).
>>>>>> Thanks,
>>>>>> David
>>>>>>> Testing: regression test, jck-runtime/java_lang, jdk/test/java/lang/
>>>>>>> Thanks!
>>>>>>> Best regards,
>>>>>>> Vladimir Ivanov

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