libjava/java/lang/VMThrowable.java

   1 /* java.lang.VMThrowable -- VM support methods for Throwable.
   2    Copyright (C) 1998, 1999, 2002 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package java.lang;
  39
  40 import gnu.gcj.runtime.NameFinder;
  41 import gnu.gcj.runtime.StackTrace;
  42
  43 /**
  44  * VM dependent state and support methods Throwable.
  45  * It is deliberately package local and final and should only be accessed
  46  * by the Throwable class.
  47  * <p>
  48  * This is the version used by libgcj (http://gcc.gnu.org/java/).
  49  *
  50  * @author Mark Wielaard (mark@klomp.org)
  51  */
  52 final class VMThrowable
  53 {
  54   private gnu.gcj.runtime.StackTrace trace;
  55
  56   /**
  57    * Private contructor, create VMThrowables with fillInStackTrace();
  58    */
  59   private VMThrowable() { }
  60
  61   /**
  62    * Fill in the stack trace with the current execution stack.
  63    * Called by <code>Throwable.fillInStackTrace()</code> to get the state of
  64    * the VM. Can return null when the VM does not support caputing the VM
  65    * execution state.
  66    *
  67    * @return a new VMThrowable containing the current execution stack trace.
  68    * @see Throwable#fillInStackTrace()
  69    */
  70   static VMThrowable fillInStackTrace(Throwable t)
  71   {
  72     VMThrowable state = null;
  73
  74     /* FIXME: size of the stack trace is limited to 128 elements.
  75        It's undoubtedly sensible to limit the stack trace, but 128 is
  76        rather arbitrary.  It may be better to configure this.  */
  77     if (trace_enabled)
  78       {
  79         state = new VMThrowable ();
  80         state.trace = new gnu.gcj.runtime.StackTrace(128);
  81       }
  82     return state;
  83   }
  84
  85   /**
  86    * Returns an <code>StackTraceElement</code> array based on the execution
  87    * state of the VM as captured by <code>fillInStackTrace</code>.
  88    * Called by <code>Throwable.getStackTrace()</code>.
  89    *
  90    * @return a non-null but possible zero length array of StackTraceElement.
  91    * @see Throwable#getStackTrace()
  92    */
  93   StackTraceElement[] getStackTrace(Throwable t)
  94   {
  95     StackTraceElement[] result;
  96     if (trace != null)
  97       {
  98         NameFinder nameFinder = new NameFinder();
  99         result = nameFinder.lookup(t, trace.stackTraceAddrs(),
 100                                    trace.length());
 101         nameFinder.close();
 102       }
 103     else
 104       result = new StackTraceElement[0];
 105
 106     return result;
 107   }
 108
 109   // Setting this flag to false prevents fillInStackTrace() from running.
 110   static boolean trace_enabled = true;
 111 }