Re: TARGET_VTABLE_USES_DESCRIPTORS breaks Java GC; Object.h problem

[Bryce McKinlay <bryce at waitaki dot otago dot ac dot nz>]

Boehm, Hans wrote:

>This gets me quite a bit further.  But it seems suboptimal,
>since it wastes 2 words in very vtable.  Is there any reason not to change
>this to:
>
>class pointer
>gc descriptor
>function descriptors (2 words each)
>...  ?
>

Assuming there is no reason not to, as far as runtime changes you should 
only need to change the _Jv_VTable definition in jvm.h, and Object.h.

>I don't fully understand all the implications of such a change.  It seems to
>me it would require conditionally imstalling a platform-dependent version of
>Object.h.  
>

Wouldn't wrapping the second dummy vtable entry with #ifdef __ia64__ be 
sufficient?

>But I think that's already necessary, at least for the trunk, to
>fix another current bug:  There's currently a
>
>#ifndef JV_HASH_SYNCHRONIZATION
>
>in Object.h.  That doesn't make any sense if Object.h is included by client
>native code.  (I put it there as a stopgap.  I think we forgot about it when
>JV_HASH_SYNCHRONIZATION was turned on by default on some platforms.)  Or am
>I missing something here?
>

Object.h includes libgcj-config.h, which is installed with 
JV_HASH_SYNCHRONIZATION defined if appropriate.

regards

Bryce.