Re: FYI: Linker & Verifier fixes (really GC mark procedures)

[Bryce McKinlay <mckinlay at redhat dot com>]

Andrew Haley wrote:
>  > The code in _Jv_MarkObj that directly traces objects referenced from
>  > class objects (instead of pushing them on the mark stack) is on very
>  > thin ice.  That's not how mark procedures are supposed to work.  In my
>  > opinion, if we could make it go away, that would be great.
>
> Indeed.  I have a patch in the pipeline that causes all objects of
> class Class to be properly allocated rather than statically allocated
> by the linker.  In turn, this has the potential to make _Jv_MarkObj
> eventually go away.
>   

Yes, _Jv_MarkObj has long been a source of bugs - it would be a big 
improvement to get rid of it.

Once we have this new class metadata scheme, the layout of jclass will 
no longer dictated by the compiler/ABI. It should be trivial to arrange 
jclass so that (eg) all the pointers that need to be marked are at the 
beginning of the object, and give it a length-based mark descriptor so 
that we maintain precise scanning.

Since we'll be allocating variable-length storage for each class's 
static fields at runtime, this would be split into one block for 
pointers, and another block for non-pointer data.

Bryce