Summary

The spec of the "can_redefine_any_class" needs to be more clear and consistent.

Problem

The spec of the "can_redefine_any_class" states:

"Can modify (retransform or redefine) any modifiable class. See IsModifiableClass."

It neglects to state: " (can_redefine_classes must also be set)".

The relationship between the capabilities "can_redefine_any_class" and "can_retransform_any_class" is also not clear.

The "can_redefine_any_class" spec states:

"Can modify (retransform or redefine)..."

which means it allows both to REDEFINE and to RETRANSFORM any class.

Then there can be a confusion on how to understand the capability "can_retransform_any_class".

So, the spec needs to be more clear.

A similar fragment in the "can_redefine_any_class" capability spec in IsModifiableClass() also needs to be fixed:

  "If possessed then all classes (except primitive, array, and some implementation defined classes)
   are modifiable (redefine or retransform)." 

Solution

The suggestion is to change two fragments in the JVMTI spec below.

Fragment #1: The "can_redefine_any_class" capability spec:

from:
   "Can modify (retransform or redefine) any modifiable class. See IsModifiableClass."

to:
  "RedefineClasses can be called on any modifiable class. See IsModifiableClass.
   (can_redefine_classes must also be set)"

Fragment #2: The "can_redefine_any_class" capability spec in the IsModifiableClass():

from:
   "If possessed then all classes (except primitive, array, and some implementation defined classes)
    are modifiable (redefine or retransform)." 

to:
  "If possessed then all classes (except primitive, array, and some implementation defined classes)
   are modifiable with RedefineClasses." 

Specification

Please, find the jvmti-specdiff.zip in the attachments. The suggested fix for spec is:

diff -r 6a60270af76b src/hotspot/share/prims/jvmti.xml
--- a/src/hotspot/share/prims/jvmti.xml Mon May 13 20:45:03 2019 -0700
+++ b/src/hotspot/share/prims/jvmti.xml Wed May 22 01:51:44 2019 -0700
@@ -7443,7 +7443,7 @@
       <capabilities>
         <capability id="can_redefine_any_class">
           If possessed then all classes (except primitive, array, and some implementation defined
-          classes) are modifiable (redefine or retransform).
+          classes) are modifiable with <functionlink id="RedefineClasses"/>.
         </capability>
         <capability id="can_retransform_any_class">
           If possessed then all classes (except primitive, array, and some implementation defined
@@ -10205,8 +10205,10 @@
       </capabilityfield>
       <capabilityfield id="can_redefine_any_class">
    <description>
-          Can modify (retransform or redefine) any modifiable class.
+          <functionlink id="RedefineClasses"/> can be called on any modifiable class.
           See <functionlink id="IsModifiableClass"/>.
+          (<fieldlink id="can_redefine_classes" struct="jvmtiCapabilities"/>
+          must also be set)
    </description>
       </capabilityfield>
       <capabilityfield id="can_get_current_thread_cpu_time">

The latest JVMTI spec specdiff is:

http://cr.openjdk.java.net/~sspitsyn/webrevs/2019/8046018-jvmti-cap-spec.3/jvmti-specdiff/

The latest JVMTI spec is:

http://cr.openjdk.java.net/~sspitsyn/webrevs/2019/8046018-jvmti-cap-spec.3/jvmti.html