RE: libgcj merging and VMStackWalker

["Jeroen Frijters" <jeroen at sumatra dot nl>]

Hi,

I still don't get it. Why can you walk up one frame from the context
class, but not two frames from the VMStackWalker class?

Regards,
Jeroen 

> -----Original Message-----
> From: java-owner@gcc.gnu.org [mailto:java-owner@gcc.gnu.org] 
> On Behalf Of Tom Tromey
> Sent: Sunday, May 14, 2006 01:42
> To: GNU Classpath Project
> Cc: GCJ Hackers
> Subject: libgcj merging and VMStackWalker
> 
> This week I spent some time looking at the libgcj/Classpath merge
> situation.  After removing all the simple merges that hadn't yet been
> handled for some reason, I looked at VMStackWalker a little.
> 
> I think this merge could be done fairly simply.  In fact I think it
> just requires adding a 'Class' argument to
> VMStackWalker.getCallingClass and VMStackWalker.getCallingClassLoader.
> This argument would name the immediate caller, and these methods
> would be changed to return the class just above the argument class in
> the stack trace.
> 
> With this change I think I could immediately merge Logger,
> ResourceBundle, Package, and parts of SecurityManager and the little
> CORBA differences.
> 
> I don't think this would overly affect performance (a big worry on the
> gcj end) or maintainability on the Classpath side.
> 
> It would require a small VM change.  However, other VMs could simply
> add this method argument and then ignore it, and things would continue
> to work as they do today.
> 
> I've appended the VMStackWalker change so folks can see what it looks
> like.  I didn't include all the other changes, which are basically
> mechanical.
> 
> On the libgcj side, VMStackWalker would be just a simple wrapper
> around the existing stack-walking code.  The class argument would make
> it simpler for our stack walker to know when to start looking for the
> 'caller' class -- it would skip both VMStackWalker and the immediate
> (internal) caller.
> 
> Comments?
> 
> Tom
> 
> Index: VMStackWalker.java
> ===================================================================
> RCS file: 
> /cvsroot/classpath/classpath/vm/reference/gnu/classpath/VMStac
> kWalker.java,v
> retrieving revision 1.6
> diff -u -r1.6 VMStackWalker.java
> --- VMStackWalker.java	13 Nov 2005 22:29:45 -0000	1.6
> +++ VMStackWalker.java	13 May 2006 23:28:36 -0000
> @@ -78,7 +78,7 @@
>     * VM implementers are encouraged to provide a more efficient
>     * version of this method.
>     */
> -  public static Class getCallingClass()
> +  public static Class getCallingClass(Class context)
>    {
>      Class[] ctx = getClassContext();
>      if (ctx.length < 3)
> @@ -97,7 +97,7 @@
>     * VM implementers are encouraged to provide a more efficient
>     * version of this method.
>     */
> -  public static ClassLoader getCallingClassLoader()
> +  public static ClassLoader getCallingClassLoader(Class context)
>    {
>      Class[] ctx = getClassContext();
>      if (ctx.length < 3)
>