Re: minimal hack to classpath for ORP 1.0.9

[Eric Blake]

Fred Gray wrote:
> 
> It's a straightforward bootstrapping problem, and it's apparently already been
> solved once in the past.  See the javadoc for Runtime.setSecurityManager():
> 
>    This was moved to Runtime so that Runtime would no longer trigger
>    System's class initializer.  Runtime does native library loading, and
>    the System class initializer requires native libraries to have been
>    loaded.
> 
> The world starts out by initializing java.lang.Object.  Its static initializer
> does a System.loadLibrary(), which causes System to be initialized.  The 
> static
> initializer for System again calls System.loadLibrary(), which in turn calls
> Runtime.load(), causing Runtime to be initialized.  The static initializer for
> Runtime calls System.getProperty(), but the properties table hasn't been
> constructed yet, so "properties.getProperty(key)" tries to follow a null
> pointer.  Therefore the world ends in a giant kaboom. :-)

I did some shuffling and analysis, and I think the latest version in
Classpath has a safe bootstrap sequence.  Can you please test it for
me?  I did not trace the initialization of ClassLoader; I'm hoping that
it does not cause problems before the native libraries are loaded, but
it appears to me that System.getProperty should now be working before
the ClassLoader initialization begins.  Quoting from the patch I made to
Runtime.defaultProperties:

...
   * No matter what class you start initialization with, it defers to
the
   * superclass, therefore Object.<clinit> will be the first Java code
   * executed. From there, the bootstrap sequence, up to the point that
   * native libraries are loaded (as of March 24, when I traced this
   * manually) is as follows:
   *
   * Object.<clinit> uses a String literal, possibly triggering
initialization
   *  String.<clinit> calls WeakHashMap.<init>, triggering
initialization
   *   AbstractMap, WeakHashMap, WeakHashMap$1 have no dependencies
   *  String.<clinit> calls CaseInsensitiveComparator.<init>, triggering
   *      initialization
   *   CaseInsensitiveComparator has no dependencies
   * Object.<clinit> calls System.loadLibrary, triggering initialization
   *  System.<clinit> calls System.loadLibrary
   *  System.loadLibrary calls Runtime.getRuntime, triggering
initialization
   *   Runtime.<clinit> calls Properties.<init>, triggering
initialization
   *    Dictionary, Hashtable, and Properties have no dependencies
   *   Runtime.<clinit> calls insertSystemProperties; the VM must make
sure
   *      that there are not any harmful dependencies
   *   Runtime.<clinit> calls Runtime.<init>
   *    Runtime.<init> calls StringTokenizer.<init>, triggering
initialization
   *     StringTokenizer has no dependencies
   *  System.loadLibrary calls Runtime.loadLibrary
   *   Runtime.loadLibrary should be able to load the library, although
it
   *       will probably set off another string of initializations from
   *       ClassLoader first
   */

2002-03-25  Eric Blake  <address@hidden>

        * vm/reference/java/lang/Runtime.java (defaultProperties): New
        field, to work around bootstrap issue.
        (securityManager): Make package visible.
        (Runtime): Remove bootstrap dependencies from constructor.
        * vm/reference/java/lang/Thread.java: Use securityManager field
        directly.
        * vm/reference/java/lang/VMSystem.java (insertSystemProperties):
        Move to Runtime, for bootstrap issue.
        * java/lang/Object.java: Document bootstrap importance.
        * java/lang/String.java: Ditto.
        * java/lang/ThreadGroup.java: Use securityManager field directly.
        * java/lang/System.java (defaultProperties): Remove, to work
        around bootstrap issue.
        * java/util/Dictionary.java: Document bootstrap importance.
        * java/util/Hashtable.java: Ditto.
        * java/util/Propeties.java: Ditto.
        * java/util/StringTokenizer.java: Ditto.
        * java/util/WeakHashMap.java: Ditto.

-- 
This signature intentionally left boring.

Eric Blake             address@hidden
  BYU student, free software programmer