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Re: patch to bring java vtables closer to g++ abi conformance
- From: Mark Mitchell <mark at codesourcery dot com>
- To: Per Bothner <per at bothner dot com>, "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Cc: "java at gcc dot gnu dot org" <java at gcc dot gnu dot org>
- Date: Wed, 23 Jan 2002 11:19:38 -0800
- Subject: Re: patch to bring java vtables closer to g++ abi conformance
- References: <3C4EF937.3060806@bothner.com>
--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