Proxy.isProxyClass scalability

[Peter Levart]

Hi David,

I was surprised to see Usafe report these offsets. See below:

java.lang.Class *instance* field offsets:

               Field Type                           Field Name Offset
               ---------- ---------- ------
              Constructor cachedConstructor     12
                    Class newInstanceCallerCache     16
                   String name     20
            SoftReference reflectionData     24
          ClassRepository genericInfo     28
                 Object[] enumConstants     32
                      Map enumConstantDirectory     36
                      Map annotations     40
                      Map declaredAnnotations     44
           AnnotationType annotationType     48
            ClassValueMap classValueMap *52*


Why the *24 bytes* gap between /classValueMap/ and /classRedefinedCount/ 
fields?

                      int classRedefinedCount *80*
                      int lastAnnotationsRedefinedCount     84

java.lang.String *static* field offsets:

               Field Type                           Field Name Offset
               ---------- ---------- ------
      ObjectStreamField[] serialPersistentFields     96
               Comparator CASE_INSENSITIVE_ORDER    100
                     long serialVersionUID    104
                      int HASHING_SEED    112


The 64 bit pointers variant:

java.lang.Class instance field offsets:

               Field Type                           Field Name Offset
               ---------- ---------- ------
              Constructor cachedConstructor     16
                    Class newInstanceCallerCache     24
                   String name     32
            SoftReference reflectionData     40
          ClassRepository genericInfo     48
                 Object[] enumConstants     56
                      Map enumConstantDirectory     64
                      Map annotations     72
                      Map declaredAnnotations     80
           AnnotationType annotationType     88
            ClassValueMap classValueMap *96*

*24 bytes* gap here too!

                      int classRedefinedCount *128*
                      int lastAnnotationsRedefinedCount    132

java.lang.String static field offsets:

               Field Type                           Field Name Offset
               ---------- ---------- ------
      ObjectStreamField[] serialPersistentFields    144
               Comparator CASE_INSENSITIVE_ORDER    152
                     long serialVersionUID    160
                      int HASHING_SEED    168


Might it be that the "classRedefinedCount" field offset is fixed somehow 
in VM, since the VM has to update it? Should there be VM changes also to 
accomodate ReflectionData changes? Are there VM fields inserted here 
that don't have a Java mapping?

Regards, Peter