patch to bring java vtables closer to g++ abi conformance

Mark Mitchell mark@codesourcery.com
Wed Jan 23 11:20:00 GMT 2002



--On Wednesday, January 23, 2002 09:56:07 AM -0800 Per Bothner 
<per@bothner.com> wrote:

> The g++ v3 abi (http://www.codesourcery.com/cxx-abi/abi.html) specifies
> that each vtable contains an offset-to-top and a type_info pointer.
> These words are *before* the word pointed to by each object's vtable
> pointer.  Thus if we add the extra header words it does not actually
> break binary compatibility, unless you look at these new fields - or the
> object's file symbols.   I.e the vtable pointer to class foo is now
> _ZTVN3fooE+8 (assuming a 32-bit target) instead of ZTVN3fooE.

Correct.  In this sense, assuming single non-virtual inheritance, the
ABI is very similar to the old ABI.

> Comments?  Anyone think I shouldn't check it in?

You didn't post the patch, but I think it sounds like a very good idea.

--
Mark Mitchell                   mark@codesourcery.com
CodeSourcery, LLC               http://www.codesourcery.com



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