View source for SableVM

{{Infobox software
| name                   = SableVM
| logo                   = SableVM Logo.png
| screenshot             =
| caption                =
| developer              = Sable Research Group at [[McGill University]]
| discontinued           = yes
| latest release version = 1.13
| latest release date    = {{Start date and age|2007|03|30}}
| latest preview version =
| latest preview date    =
| operating system       = [[Cross-platform]]
| programming language   =
| genre                  = [[Java Virtual Machine]]
| license                = [[GNU Lesser General Public License]]
| website                = {{URL|http://sablevm.org/}}
}}
'''SableVM''' was a [[Clean room design|clean room implementation]] of [[Java platform|Java]] [[bytecode]] [[Interpreter (computing)|interpreter]] implementing the [[Java virtual machine]] ([[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.{{citation needed|date=November 2012}} It is now no longer being maintained.

The implementation was a part of the effort in the early 2000s to break the [[Java (programming language)|Java]] ecosystem free from [[Sun Microsystems]]'s control.<ref>{{cite web|url=http://www.theinquirer.net/inquirer/news/1027066/sun-approved-open-source-java-making-progress |archive-url=https://web.archive.org/web/20091203151009/http://www.theinquirer.net/inquirer/news/1027066/sun-approved-open-source-java-making-progress |url-status=unfit |archive-date=December 3, 2009 |title=Sun-approved Open Source java making progress |publisher=The Inquirer |date=2006-03-31 |accessdate=2012-12-02}}</ref><ref>{{cite web |url=http://onlamp.com/pub/wlg/6725 |title=O'Reilly Network wins a Jolt; SNAP Platform gets jolted |publisher=Onlamp.com |date= |accessdate=2012-12-02 |archive-date=2016-03-03 |archive-url=https://web.archive.org/web/20160303231206/http://www.onlamp.com/pub/wlg/6725 |url-status=dead }}</ref><ref>{{cite web|url=http://tv.sys-con.com/node/273937?page=0,1 |title=Barbarians at the Gate &#124; SYS-CON.TV |publisher=Tv.sys-con.com |date=2006-09-22 |accessdate=2012-12-02}}</ref>

==Overview==

The core engine is an [[Interpreter (computing)|interpreter]] which used ground-breaking techniques to deliver performance that can approach that of a "naive" [[just-in-time compilation|just-in-time (JIT) compiler]], while retaining the [[software engineering]] advantages of interpreters: [[Porting|portability]], [[maintainability]] and [[simplicity]].<ref>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.</ref><ref>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.</ref> 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 [[Free Software Foundation|FSF]]) which is licensed under the [[GPL linking exception|GNU General Public License with linking exception]].

SableVM is the first [[open-source software|open-source]] virtual machine for Java to include the support for [[JVMDI]] (Java Virtual Machine Debugging Interface) and [[JDWP]] (Java Debug Wire Protocol).{{Citation needed|date=August 2008}} These standard Java debugging interfaces are used for example by [[Eclipse (software)|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 (programming language)|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.<ref>Eng, David. "JIL: an extensible intermediate language." Sable Research Group, McGill University (2002).</ref><ref>Eng, David. Combining static and dynamic data in code visualization. Vol. 28. No. 1. ACM, 2002.</ref> The language has not been widely adopted.

Consider the following piece of Java code.
<syntaxhighlight lang="Java">
public MyClass implements MyInterface extends MySupperClass {
  int MyField;

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

This piece can be expressed in the language, as follows:
<syntaxhighlight lang="xml">
<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>
</syntaxhighlight>

== See also ==
{{Portal|Free and open-source software|Computer programming}}
* [[List of Java virtual machines]]
* [[Free Java implementations]]

==References==
{{Reflist}}

==External links==
* {{Official website|http://www.sablevm.org/}}
* [https://web.archive.org/web/20060104214933/http://sablevm.org/devel/ SableVM Development sub-site]
* [https://web.archive.org/web/20050415051821/http://sablevm.org/wiki/Debug Information on debugging with SableVM and Eclipse]
* [http://www.sable.mcgill.ca/jil/class.xml Java Intermediate Language]

{{Java Virtual Machine}}

[[Category:Cross-platform software]]
[[Category:Discontinued Java virtual machines]]