[cp-patches] Patch: Thread addon for shutdown hooks.

[Guilhem Lavaux]

Hi list,

While merging the VMThread model in kaffe, I've noticed that Runtime 
does not check whether hooks had already been started when they are 
being added. So I've added one small method to Thread and the 
corresponding checking in Runtime.addShutdownHook. The error reporting 
has also been improved by providing messages to exceptions.

Comments ?

Guilhem.

ChangeLog Entry:

2004-07-30  Guilhem Lavaux <address@hidden>

   * java/lang/Thread.java
   (hasDied): New method.
   (alreadyStarted): New field.
   (die): Set alreadyStarted to true.
   * java/lang/Runtime.java
   (addShutdownHook): Check whether the hook has already been started 
and has
   died. Improved error messages.

Index: java/lang/Runtime.java
===================================================================
RCS file: /cvsroot/classpath/classpath/java/lang/Runtime.java,v
retrieving revision 1.7
diff -u -r1.7 Runtime.java
--- java/lang/Runtime.java      30 Apr 2004 15:22:41 -0000      1.7
+++ java/lang/Runtime.java      30 Jul 2004 08:32:37 -0000
@@ -341,16 +341,16 @@
     SecurityManager sm = securityManager; // Be thread-safe!
     if (sm != null)
       sm.checkPermission(new RuntimePermission("shutdownHooks"));
-    if (hook.isAlive() || hook.getThreadGroup() == null)
-      throw new IllegalArgumentException();
+    if (hook.isAlive() || hook.hasDied() || hook.getThreadGroup() == null)
+      throw new IllegalArgumentException("The hook thread " + hook + " must 
not have been already run or started");
     synchronized (libpath)
       {
         if (exitSequence != null)
-          throw new IllegalStateException();
+          throw new IllegalStateException("The Virtual Machine is exiting. It 
is not possible anymore to add any hooks");
         if (shutdownHooks == null)
           shutdownHooks = new HashSet(); // Lazy initialization.
         if (! shutdownHooks.add(hook))
-          throw new IllegalArgumentException();
+          throw new IllegalArgumentException(hook.toString() + " had already 
been inserted");
       }
   }
 
Index: java/lang/Thread.java
===================================================================
RCS file: /cvsroot/classpath/classpath/java/lang/Thread.java,v
retrieving revision 1.8
diff -u -r1.8 Thread.java
--- java/lang/Thread.java       29 Jun 2004 10:04:41 -0000      1.8
+++ java/lang/Thread.java       30 Jul 2004 08:32:38 -0000
@@ -130,6 +130,9 @@
   /** The next thread number to use. */
   private static int numAnonymousThreadsCreated;
 
+  /** True if the thread has already been started */
+  private boolean alreadyStarted;
+
   /**
    * Allocates a new <code>Thread</code> object. This constructor has
    * the same effect as <code>Thread(null, null,</code>
@@ -968,5 +971,14 @@
   {
     group.removeThread(this);
     vmThread = null;
+    alreadyStarted = true;
+  }
+
+  /**
+   * Returns true if the thread had already been started once.
+   */
+  final boolean hasDied()
+  {
+    return alreadyStarted;
   }
 }