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List:       openjdk-serviceability-dev
Subject:    Re: RFC: 8223915: JVMTI Spec: can_redefine_any_class capability spec is inconsistent
From:       David Holmes <david.holmes () oracle ! com>
Date:       2019-05-16 22:01:25
Message-ID: 8e1a11e8-0c12-caca-47b9-82a0575fc975 () oracle ! com
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On 17/05/2019 2:40 am, serguei.spitsyn@oracle.com wrote:
> Hi David,
> 
> 
> On 5/16/19 05:33, David Holmes wrote:
> > On 16/05/2019 7:47 pm, serguei.spitsyn@oracle.com wrote:
> > > On 5/16/19 02:25, David Holmes wrote:
> > > > Hi Serguei,
> > > > 
> > > > On 16/05/2019 5:22 pm, serguei.spitsyn@oracle.com wrote:
> > > > > **Note #2*
> > > > > 
> > > > > Just realized there is an incorrectness in current spec of this 
> > > > > capability an_redefine_any_class.
> > > > > 
> > > > > This section
> > > > > https://docs.oracle.com/en/java/javase/11/docs/specs/jvmti.html#jvmtiCapabilities.can_redefine_any_class \
> > > > >  
> > > > > 
> > > > > tells:
> > > > > "Can modify (retransform or redefine) any modifiable class."
> > > > > 
> > > > > It is just wrong. Instead, it should tell:
> > > > > "Can modify (retransform or redefine) any class except primitive, 
> > > > > array,
> > > > > and some implementation defined classes."
> > > > 
> > > > But that's what it does say by saying "any modifiable class".
> > > 
> > > I understand your confusion as I have it as well. :)
> > > 
> > > The problem is that in the IsModifiableClass spec the affect of 
> > > capability is explained as:
> > > "If possessed then all classes (except primitive, array, and some 
> > > implementation
> > > defined classes) are modifiable (redefine or retransform)."
> > > 
> > > So that successful possession of this capability makes all classes
> > > (except primitive, etc.) to be modifiable.
> > 
> > Yes and so:
> > 
> > "Can modify (retransform or redefine) any modifiable class."
> > 
> > means
> > 
> > "Can modify (retransform or redefine) any class (except primitive, etc)."
> > 
> > I'm not seeing the problem. ??
> 
> 
> The problem is that this statement is confusing:
> "Can modify (retransform or redefine) any modifiable class."
> 
> It is because possessing the capability makes ALL the classes (except 
> primitive, array, ...) modifiable.
> Which means that there can be non-modifiable classes other than 
> primitive, array, and some implementation defined classes."

Again I don't see any issue. All classes except primitive, array, ... 
are potentially modifiable but you need the actual capability to be able 
to modify them.

David
-----

> Thanks,
> Serguei
> 
> > 
> > David
> > 
> > > Thanks,
> > > Serguei
> > > 
> > > 
> > > > David
> > > > -----
> > > > 
> > > > > In another place it is defined as:
> > > > > "If possessed then all classes (except primitive, array, and some 
> > > > > implementation
> > > > > defined classes) are modifiable (redefine or retransform). "
> > > > > 
> > > > > For reference, see the section "Optional Features" here:
> > > > > https://docs.oracle.com/en/java/javase/11/docs/specs/jvmti.html#IsModifiableClass \
> > > > >  
> > > > > 
> > > > > I'll update the CSR to fix this issue.
> > > > > 
> > > > > Thanks,
> > > > > Serguei
> > > > > 
> > > > > > 
> > > > > > -Alan
> > > > > 
> > > 
> 


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