On Mon, 2005-07-25 at 18:20 +0200, Mark Wielaard wrote:
> On Mon, 2005-07-25 at 17:55 +0200, Jeroen Frijters wrote:
> > > This won't work if you make the VM_USE_CACHE field static final. Then
> > > the constant will be compiled into ClassLoader making it impossible to
> > > override for the runtime vm-classes later. It has to be a
> > > static method for that to work.
> >
> > Like Archie says, your comment doesn't make sense ;-) If a VM decides
> > not to use the cache in ClassLoader, it replaces VMClassLoader and sets
> > the constant to true.
>
> Yes, but unfortunately that doesn't change the byte-code of the
> ClassLoader class. static final primitive (and String) field values are
> actually inlined into other classes. So you can replace VMClassLoader
> all you want with a version the has VM_USE_CACHE set to another value,
> that won't actually change the ClassLoader code paths unless ClassLoader
> is also recompiled against this new value. Really, try it out. It is an
> annoying byte code optimization. So for things that can be different at
> runtime like the VMClasses you unfortunately cannot use static final
> fields of primitive types.
>
> > I haven't looked at jdwp yet, but hopefully jdwp will provide its own
> > VM interface instead of messing around with the internals of other
> > classes.
>
> Yeah that would be the clean way to do it indeed.
Well if it were decided to have some minor changes to allow VM re-use
this is pretty much how I would alter ClassLoader.
We're not ready to use it anyways but I'll put it out there so people
know what would be required.
Aaron
Index: java/lang/ClassLoader.java
===================================================================
RCS file: /cvsroot/classpath/classpath/java/lang/ClassLoader.java,v
retrieving revision 1.54
diff -u -p -r1.54 ClassLoader.java
--- java/lang/ClassLoader.java 25 Jul 2005 14:28:42 -0000 1.54
+++ java/lang/ClassLoader.java 25 Jul 2005 18:37:38 -0000
@@ -40,6 +40,7 @@ package java.lang;
import gnu.classpath.SystemProperties;
import gnu.classpath.VMStackWalker;
+import gnu.classpath.jdwp.Jdwp;
import gnu.java.util.DoubleEnumeration;
import gnu.java.util.EmptyEnumeration;
@@ -152,6 +153,14 @@ public abstract class ClassLoader
*/
private final boolean initialized;
+ /**
+ * This list is kept around for JDWP. We need a way to know every class
+ * that this ClassLoader has been asked to load, thus they will be added
+ * here. There's no need to do anything else, JDWP is able to sniff out
+ * private fields so we'll just sniff this field as well!
+ */
+ final ArrayList loadRequests = new ArrayList();
+
static class StaticData
{
/**
@@ -333,23 +342,25 @@ public abstract class ClassLoader
{
if (parent == null)
{
- c = VMClassLoader.loadClass(name, resolve);
- if (c != null)
- return c;
- }
- else
- {
- return parent.loadClass(name, resolve);
- }
- }
- catch (ClassNotFoundException e)
- {
- }
- // Still not found, we have to do it ourself.
- c = findClass(name);
+ c = VMClassLoader.loadClass(name, resolve);
+ }
+ else
+ {
+ c = parent.loadClass(name, resolve);
+ }
+ }
+ catch (ClassNotFoundException e)
+ {
+ }
+ // Still not found, we have to do it ourself.
+ if (c == null)
+ c = findClass(name);
}
+ }
if (resolve)
resolveClass(c);
+ if (Jdwp.isDebugging)
+ loadRequests.add(c);
return c;
}
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