Clarifications and Amendments to the Java Virtual Machine Specification

Synthetic Attribute

The specification of the synthetic attribute in JVMS 4.7.6, states:

A class member that does not appear in the source code must be marked using a Synthetic attribute.

This is inaccurate with respect to both JLS 2nd edition and the reference implementation. The text should be revised to state

A class member that does not appear in the source code must be marked using a Synthetic attribute, except for the default constructor and the class initialization method.

Lookup Algorithm for Invokevirtual Instruction

The lookup algorithm used by the invokevirtual instruction (pages 291-292 of the JVMS, 2nd edition) should be revised as follows:

Let C be the class of the target of the method invocation. The actual method to be invoked is selected by the following lookup procedure:
If C contains a declaration for an instance method M with the same name and descriptor as the resolved method, and M overrides the resolved method , then M is the method to be invoked, and the lookup procedure terminates.

Otherwise, if C has a superclass, this same lookup procedure is performed recursively using the direct superclass of C ; the method to be invoked is the result of the recursive invocation of this lookup procedure.

Otherwise, an AbstractMethodError is raised.

The text highlighted in red is the only change. It replaces the text

and the resolved method is accessible from C

in the current specification. See the revision of the definition of method override in the JLS 3rd Edition page for more details.

Changes for JDK 1.5

The following changes to the Java Virtual Machine Specification Second Edition are planned were made in JDK 1.5. These changes are part of JSR45 and JSR 924

The Structure of the Java Virtual Machine (Chapter 3) - Changes to this chapter are given in revisions to "The Structure of the Java Virtual Machine" (422k PDF).
The class File Format (Chapter 4) - The class file format will undergo minor modifications to support changes mandated by JSR-14, JSR45, JSR-175 and JSR-201, as well as minor corrections and adjustments. These changes are given in revisions to "The class File Format" (494k PDF). Changes covered by JSRs 14, 175 and 201 are denoted by change bars and colored text.
Loading, Linking and Initializing (Chapter 5) - Changes to this chapter are given in revisions to "Loading, Linking and Initializing" (234k PDF).

Instruction Set (Chapter 6) - The ldc instruction is generalized to support references to classes, in order to make class literals more efficient. The putfield and putstatic instructions have slight modifications as a result of JSR133. The changes to the specification are given in revisions to "The Java Virtual Machine Instruction Set" (1954k PDF).

Memory Model (Chapter 8) - JSR133 has changed the memory model. Chapter 8 of the JVMS 2nd edition is superceded by JSR133. See chapter 17 of the JLS, 3rd edition for details.