RFR: 8035150 ShouldNotReachHere() in ConstantPool::copy_entry_to

[Staffan Larsen]

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 ? ;)

> - 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?

/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
>