Re: [Jikesrvm-researchers] JikesRVM confused by certain files compiled with '-target 1.4'

[David P G. <gr...@us...>]

jik...@li... wrote on 08/16/2005 
06:57:02 PM:

> What version of the JVM and JLS specs does JikesRVM aspire to? 

I think it's fair to say we aspire to 1.4, but some features of 1.4 aren't 
there yet.  Of course legally speaking Jikes RVM isn't a JVM at all, so in 
some sense this isn't an entirely well-formed question. ;-)

I'd encourage you to open a bug report against Jikes RVM with your example 
program (and a patch with a proposed fix would be fantastic if you happen 
to have the time to dig in and look).  My guess is that this would be 
relatively simple to fix. 
 
> I've got a demo which, if compiled with jikes or with 'javac -target
> 1.4' will cause JikesRVM to abort with an exception, but compiled with
> 'javac -target 1.2' will work.  I'm wondering if this is a bug, or if
> JikesRVM isn't trying to play at the 1.4 level.
> 
> The demo is this, put in a file called TestImpl.java:
> ------------------------------------------------------------
> interface DummyIF {static final Integer BASE_FIELD = new Integer(6);}
> public class TestImpl implements DummyIF {
>     public static final int TEST_FIELD = BASE_FIELD.intValue();
>     public static void main(String argv[]) {
>    System.out.println("Value: " + TEST_FIELD);
>     }
> }
> ------------------------------------------------------------
> 
> The execution surprise exhibits like this:
> ------
> > javac -target 1.2 TestImpl.java
> > rvm TestImpl
> Value: 6
> > javac -target 1.4 TestImpl.java
> > rvm TestImpl
> Exception in thread "main": java.lang.ExceptionInInitializerError: While 

> initializing TestImpl
>         at 
com.ibm.JikesRVM.classloader.VM_Class.initialize(VM_Class.java:1414)
> Caused by: java.lang.NullPointerException
>         at TestImpl.<clinit>(TestImpl.java:5)
>         at 
com.ibm.JikesRVM.classloader.VM_Class.initialize(VM_Class.java:1410)
> JikesRVM: exit 113
> ------
> 
> The source of the difference seems to be that at 1.2, the constant
> pool entry for BASE_FIELD in TestImpl.class refers to it as
> DummyIF.BASE_FIELD, whereas with 1.4 (or with jikes, which defaults to
> 1.4 semantics) the entry in TestImpl.class refers to it as
> TestImpl.BASE_FIELD.  In the latter case, in JikesRVM
> 'fieldRef.needsDynamicLink(method)' returns false, which causes
> DummyIF never to get initialized.
> 
> At first I thought this was a bug in the jikes compiler, and I made a
> suitable fool of myself over on their bug tracker and mailing list
> getting straightened out.  I figure before I submit a bug against
> JikesRVM, I should ask if this is a real bug, or just an artifact of
> JikesRVM targetting an earlier version of the specs.
> 
> Thanks,
> Jeremy