/*
* This file is part of the Jikes RVM project (http://jikesrvm.org).
*
* This file is licensed to You under the Eclipse Public License (EPL);
* You may not use this file except in compliance with the License. You
* may obtain a copy of the License at
*
* http://www.opensource.org/licenses/eclipse-1.0.php
*
* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership.
*/
package org.vmmagic;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
/**
* The Unboxed annotation marks a type as unboxed. Besides the primitive types, all Java values
* are boxed types. Conceptually, they are represented by a pointer to a heap object. However,
* an unboxed type is represented by the value itself. All methods on an unboxed type are
* {@link Intrinsic}s.
*
* <p>As an unboxed type is not a regular java object there are a few constraints on the way unboxed
* types are handled;</p>
* <ul>
* <li>All methods are {@link Intrinsic} and thus there can be no virtual methods.</li>
* <li>An unboxed type can not be synchronized on.</li>
* <li>An unboxed type has no hashcode.</li>
* <li>An unboxed type MUST NOT be passed where an object is expected or when two overloaded methods
* can only be distinguished by by Object vs unboxed parameter type.</li>
* </ul>
*
* <p>NOTE: At the current time the Unboxed annotation is only used for documentation
* purposes but in the near future it is expected that the semantics of the annotation will
* be enforced by the compiler.</p>
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Inherited
public @interface Unboxed { }