RFR: 8035150 ShouldNotReachHere() in ConstantPool::copy_entry_to

Daniel D. Daugherty daniel.daugherty at oracle.com
Wed Feb 26 14:03:55 UTC 2014

On 2/26/14 1:31 AM, Staffan Larsen wrote:
> On 26 feb 2014, at 01:48, Daniel D. Daugherty <daniel.daugherty at oracle.com> wrote:
>> I concur with Markus. Pairing JVM_CONSTANT_UnresolvedClassInError with
>> JVM_CONSTANT_UnresolvedClass in the ConstantPool::copy_entry_to()
>> switch looks like the right thing to do.
> Good - thanks.
>> The usual questions:
>> - why wasn't this failure mode seen before JDK8?
> No tests for this ? ;)

I should have been more clear... :-) Why hasn't the NetBeans profiler
run into this before? That profiler is a wonderful test for the
RedefineClasses/RetransformClasses stuff...

>> - was this failure caught somewhere else before JDK8 and changes
>>   in JDK8 exposed a new code path?
>> Reasoning about this from a 30,000 foot view, I don't see any reason
>> why you can't redefine a class that has a constant pool ref that
>> refers to a class in error. You won't be able to use the error'ed
>> class, but there's no reason it can't be in there... Or does that
>> violate the rule that you can't redefine a class that isn't fully
>> linked (what ever that means...)???
>> So what does your new test on JDK7 or JDK6? Just curious…
> The test passes on jdk7, but fails on jdk8. (I don’t have a jdk6). I don’t know why it passes on jdk7, do you think it’s important to track it down?

The fact that it passes on JDK7 is the useful piece of data.
Figuring out why is much less important. BTW, which JDK7
version? One of the updates or GA/FCS?


> /Staffan
>> Dan
>> On 2/24/14 2:42 AM, Markus Gronlund wrote:
>>> Hi Staffan,
>>> I would think this is the correct fix.
>>> The other two constant pool "error" tags, besides UnresolvedClassInError, which signal constant pool resolution errors are MethodTypeInError and MethodHandleInError - these error tags are associated with their corresponding "success" tags in switch targets in ConstantPool::copy_entry_to(), as well as in additional routines in constantPool.cpp.
>>> In addition, in other routines in ConstantPool.cpp, the error tag JVM_CONSTANT_UnresolvedClassInError is associated with JVM_CONSTANT_UnresolvedClass -  ConstantPool::resolve_constant_at_impl() for example.
>>> Thanks
>>> Markus
>>> -----Original Message-----
>>> From: Staffan Larsen
>>> Sent: den 21 februari 2014 15:11
>>> To: hotspot-runtime-dev; serviceability-dev at openjdk.java.net serviceability-dev at openjdk.java.net
>>> Subject: RFR: 8035150 ShouldNotReachHere() in ConstantPool::copy_entry_to
>>> This is an attempt to solve a crash while redefining a class that has unresolved class references in its constant pool. I would appreciate some extra scrutiny here since I am unfamiliar with this code path.
>>> I have also added a test that causes a JVM crash without the fix.
>>> The updates to the test library is all code copied from the jdk version of the test library.
>>> webrev: http://cr.openjdk.java.net/~sla/8035150/webrev.00/
>>> bug: https://bugs.openjdk.java.net/browse/JDK-8035150
>>> Thanks,
>>> /Staffan

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