Re: Add a Field to java.lang.Object

[Andrew Haley <aph@redhat.com>]

On 06/08/2011 06:20 PM, Noah Heusser wrote:

> I'm trying to add an new extra field into java.lang.Object. I need that
> to do some memory synchronization via Network.
> 
> If I just insert the new Field in libjava/java/lang/Object.h (access
> form the Java World is not needed) I get a segmentation fault whenever I
> try to run a Java Software using that Object.h. (It does no matter
> whether I add it to _JvObjectPrefix or java::lang::Object)
> 
> If the JV_HASH_SYNCHRONIZATION Preprocessor Variable is not defined an
> extra Filed sync_info gets inserted in Object.h.
> But everywhere where extra Code is inserted depending on
> JV_HASH_SYNCHRONIZATION it seems to deal with whether or not the Garbage
> Collector needs to scan the Object.
> 
> If I add the Field in libjava/java/lang/Object.java I get a compile
> Error when I compile gcj:
> ../../../../gcc-src/libjava/java/lang/Object.java:517:0: internal
> compiler error: Segmentation fault
> 
> What extra change is needed after adding a Filed to Object?

Add it to libjava/java/langObject.h
and gcc/java/class.c in make_class_data() after sync_info.
It must be after the GC bitmap marking descriptor.  Be aware that the offset
from the start of the object is used in the marking descriptor.  You're going
to have to get used to the way that works.

I think that's it, but you'll have to try it.

Andrew.