Re: [PATCH] Fix for Hashtable contains blowing up the stack

[Dalibor Topic]

Dalibor Topic wrote:
> Hi all,
>
> attached is my fix to make ant (I think) work again with Classpath, 
> fixing the bug reported by Jim Pick here [1]
>
> Citing myself [2]:
> this is a typical java library bug, and I've both produced and fixed a 
> couple of those myself ;) You get an infinite recursion through calling 
> overridden methods. Class A in library implements public methods b and 
> c, where b internally (and of course undocumentedly ;) calls c. Class B 
> from some user of the library extends A and overrides c to call b. When 
> the user calls the method b of class B it goes straight into an infinite 
> loop.
>
> The fix is to avoid calling overridable methods from overridable 
> methods, and to delegate those calls to internal, non-overridable 
> versions of the methods.
>
> 2003-11-21  Dalibor Topic <address@hidden>
>
>         * libraries/javalib/java/util/Hashtable.java:
>         (internalcontainsValue) new method.
>         (contains, containsValue) delegate to internalContainsValue.
>
>         Reported by: Jim Pick <address@hidden>
>
> cheers,
> dalibor topic
>
> [1] http://mail.gnu.org/archive/html/classpath/2003-09/msg00009.html
> [2] http://mail.gnu.org/archive/html/classpath/2003-09/msg00016.html

And this time, I even attached the patch! ;)

cheers,
dalbor topic

--- /var/tmp/PROJECTS/classpath//./java/util/Hashtable.java     Wed Nov 12 
21:56:20 2003
+++ /tmp/topic/kaffe/libraries/javalib/java/util/Hashtable.java Fri Oct 10 
18:49:09 2003
@@ -333,7 +333,10 @@
    */
   public synchronized boolean contains(Object value)
   {
-    return containsValue(value);
+    /* delegate to non-overridable worker method 
+     * to avoid blowing up the stack.
+     */
+    return internalContainsValue(value);
   }
 
   /**
@@ -349,6 +352,25 @@
    * @since 1.2
    */
   public boolean containsValue(Object value)
+  {
+    /* delegate to non-overridable worker method 
+     * to avoid blowing up the stack.
+     */
+    return internalContainsValue(value);
+  }
+
+  /**
+   * Returns true if this Hashtable contains a value <code>o</code>, such that
+   * <code>o.equals(value)</code>. This is an internal worker method
+   * called by <code>contains()</code> and <code>containsValue()</code>.
+   *
+   * @param value the value to search for in this Hashtable
+   * @return true if at least one key maps to the value
+   * @see #contains(Object)
+   * @see #containsKey(Object)
+   * @throws NullPointerException if <code>value</code> is null
+   */
+  private boolean internalContainsValue(Object value)
   {
     for (int i = buckets.length - 1; i >= 0; i--)
       {