SableVM

SableVM was a clean room implementation of Java bytecode interpreter implementing the Java virtual machine (VM) specification, second edition. SableVM was designed to be a robust, extremely portable, efficient, and fully specifications-compliant (JVM spec, Java Native Interface, Invocation interface, Debug interface, etc.) Java Virtual Machine that would be easy to maintain and to extend. It is now no longer being maintained.

SableVM
Developer(s)Sable Research Group at McGill University
Final release
1.13 / March 30, 2007 (2007-03-30)
Repository
Operating systemCross-platform
TypeJava Virtual Machine
LicenseGNU Lesser General Public License
Websitesablevm.org

The implementation was a part of the effort in the early 2000s to break the Java ecosystem free from Sun Microsystems's control.[1][2][3]

Overview

The core engine is an interpreter which used ground-breaking techniques to deliver performance that can approach that of a "naive" just-in-time (JIT) compiler, while retaining the software engineering advantages of interpreters: portability, maintainability and simplicity.[4][5] This simplicity makes SableVM's source code very accessible and easy to understand for new users/programmers.

SableVM is Free Software — it is licensed under the GNU Lesser General Public License (LGPL). It also makes use of GNU Classpath (copyrighted by the FSF) which is licensed under the GNU General Public License with linking exception.

SableVM is the first open-source virtual machine for Java to include the support for JVMDI (Java Virtual Machine Debugging Interface) and JDWP (Java Debug Wire Protocol). These standard Java debugging interfaces are used for example by Eclipse to provide a rich and user-friendly Java development environment.

Java Intermediate Language

Some versions of the SableVM use Java Intermediate Language, an intermediate language (which is a subset of XML) representing the type structure of a Java program. The language was proposed by the team of SableVM in McGill University in January 2002 to aid the analysis of a Java program with the goals of scalability and good performance.[6][7] The language has not been widely adopted.

Consider the following piece of Java code.

public MyClass implements MyInterface extends MySupperClass {
  int MyField;

  void MyMethod (double x, double y) {
    double z;
    z = x + y;
    this.MyField = z
  }
}

This piece can be expressed in the language, as follows:

<jil>
<class name="MyClass" extends="MySupperClass">
  <modifiers><modifier name="public" /></modifiers>
  <interfaces><interface name="myinterface" /></interfaces>
    
  <fields>
    <field name="MyField" type="int" />
  </fields>

  <methods>
    <method name="MyMethod" returntype="void">
    <parameters>
      <parameter name="x" type="double" />
      <parameter name="y" type="double" />
    </parameters>
    <locals>
      <local name="z" type="double" />
    </locals>
    <statements>
      <!-- Each statement is expressed by some intermediate format for
           code generator like three address code. In the below
           a language called baf is used. -->
      <baf>
        <![CDATA[
          $r2 = $r0 + $r1;
          this.MyField = (double) $r2;
        ]]>
        <!-- Here, we are assuming x is expressed as $r0, y $r1 and z $r2. -->
      </baf>
    </statements>
    </method>
  </methods>
</class>
</jil>
gollark: Unicode™!
gollark: Yes, that is actually B.
gollark: Advantages of 128-character full-charset names:- /view/n/ pages would still only hold one unique dragon- greater opportunities for creativity via use of anomalous Unicode- essentially infinite quantity of available names- can reuse names through use of invisible characters and/or homoglyphs- more efficient lyrical lineages - fewer dragons required per word- could store 2048 bits of data per name via base65536- can name them after people/things in other languagesDisadvantages:~~- cannot actually distinguish some names without a hexdump or something- pretty hard for people to actually use without knowledge of ridiculous Unicode stuff~~ none whatsoever
gollark: Yep!
gollark: "Bob" and "Bοb" for instance.

See also

References
  1. "Sun-approved Open Source java making progress". The Inquirer. 2006-03-31. Retrieved 2012-12-02.
  2. "O'Reilly Network wins a Jolt; SNAP Platform gets jolted". Onlamp.com. Retrieved 2012-12-02.
  3. "Barbarians at the Gate | SYS-CON.TV". Tv.sys-con.com. 2006-09-22. Retrieved 2012-12-02.
  4. Gagnon, Etienne M., and Laurie J. Hendren. "SableVM: A research framework for the efficient execution of Java bytecode." Proceedings of the Java Virtual Machine Research and Technology Symposium. Vol. 1. 2001.
  5. Prokopski, Gregory B., Etienne M. Gagnon, and Christian Arcand. Bytecode testing framework for SableVM code-copying engine. Technical Report SABLETR-2007-9, Sable Research Group, School of Computer Science, McGill University, Montréal, Québec, Canada, 2007.
  6. Eng, David. "JIL: an extensible intermediate language." Sable Research Group, McGill University (2002).
  7. Eng, David. Combining static and dynamic data in code visualization. Vol. 28. No. 1. ACM, 2002.
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