Re: [Kissme-general] More Classpath change problems

[Eric Blake]

I cleaned your patch up a bit, and once I get it to compile, I'm
committing it. Thanks for the catch - I documented that the class
specified by java.system.class.loader must now have a constructor which
accepts a parent class loader.

John Leuner wrote:
> 
> I tracked this down to the ClassLoader class.
> 
> 
> Otherwise getSystemClassLoader gets in an infinite loop where the Constructor 
> for SystemClassLoader calls the ClassLoader() constructor which tries to use 
> the system class loader as the parent classloader and round and round it goes 
> ...
> 
> John Leuner
> 

2002-03-28  John Leuner  <address@hidden>

        * java/lang/ClassLoader.java (getSystemClassLoader): Break
        infinite loop by specifying parent classloader.
        * gnu/java/lang/SystemClassLoader.java (SystemClassLoader): Add
        proper constructor.

-- 
This signature intentionally left boring.

Eric Blake             address@hidden
  BYU student, free software programmer

Index: gnu/java/lang/SystemClassLoader.java
===================================================================
RCS file: /cvsroot/classpath/classpath/gnu/java/lang/SystemClassLoader.java,v
retrieving revision 1.1
diff -u -r1.1 SystemClassLoader.java
--- gnu/java/lang/SystemClassLoader.java        22 Mar 2002 21:25:20 -0000      
1.1
+++ gnu/java/lang/SystemClassLoader.java        28 Mar 2002 21:36:04 -0000
@@ -64,6 +64,17 @@
 
   /** Flag to avoid infinite loops. */
   private static boolean is_trying;
+
+  /**
+   * Creates a class loader. Note that the parent may be null, when this is
+   * created as the system class loader by ClassLoader.getSystemClassLoader.
+   *
+   * @param parent the parent class loader
+   */
+  public SystemClassLoader(ClassLoader parent)
+  {
+    super(parent);
+  }
     
   /**
    * Get the URL to a resource.
Index: java/lang/ClassLoader.java
===================================================================
RCS file: /cvsroot/classpath/classpath/java/lang/ClassLoader.java,v
retrieving revision 1.16
diff -u -r1.16 ClassLoader.java
--- java/lang/ClassLoader.java  22 Mar 2002 21:25:20 -0000      1.16
+++ java/lang/ClassLoader.java  28 Mar 2002 21:36:05 -0000
@@ -48,6 +48,7 @@
 import java.util.Enumeration;
 import java.util.HashMap;
 import java.util.Map;
+import gnu.java.lang.SystemClassLoader;
 import gnu.java.util.DoubleEnumeration;
 import gnu.java.util.EmptyEnumeration;
 
@@ -685,7 +686,8 @@
    * property <code>java.class.path</code>. This is set as the context
    * class loader for a thread. The system property
    * <code>java.system.class.loader</code>, if defined, is taken to be the
-   * name of the class to use as the system class loader, otherwise this
+   * name of the class to use as the system class loader, which must have
+   * a public constructor which takes a ClassLoader as a parent; otherwise this
    * uses gnu.java.lang.SystemClassLoader.
    *
    * <p>Note that this is different from the bootstrap classloader that
@@ -713,12 +715,28 @@
                                            "gnu.java.lang.SystemClassLoader");
         try
           {
-            return (ClassLoader) Class.forName(loader).newInstance();
+            // Give the new system class loader a null parent.
+            Constructor c = Class.forName(loader).getConstructor
+              ( new Class[] { ClassLoader.class } );
+            return (ClassLoader) c.newInstance(new Object[1]);
           }
         catch (Exception e)
           {
-            throw (Error) new InternalError
-              ("System class loader could not be found: " + e).initCause(e);
+            try
+              {
+                System.err.println("Requested system classloader "
+                                   + loader + " failed, trying "
+                                   + "gnu.java.lang.SystemClassLoader");
+                e.printStackTrace();
+                // Fallback to gnu.java.lang.SystemClassLoader.
+                return new SystemClassLoader(null);
+              }
+            catch (Exception e1)
+              {
+                throw (Error) new InternalError
+                  ("System class loader could not be found: " + e)
+                  .initCause(e);
+              }
           }
       }
     // Check if we may return the system classloader