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Re: [PATCH] 2.95: turn off DEFAULT_VTABLE_THUNKS
- To: Fergus Henderson <fjh at cs dot mu dot oz dot au>
- Subject: Re: [PATCH] 2.95: turn off DEFAULT_VTABLE_THUNKS
- From: "David O'Brien" <obrien at FreeBSD dot org>
- Date: Sat, 14 Apr 2001 10:02:33 -0700
- Cc: gcc-patches at gcc dot gnu dot org
- Organization: The NUXI BSD group
- References: <20010414011035.A33142@dragon.nuxi.com> <20010415025354.B836@hg.cs.mu.oz.au>
- Reply-To: obrien at FreeBSD dot org
On Sun, Apr 15, 2001 at 02:53:54AM +1000, Fergus Henderson wrote:
> > -/* Use more efficient ``thunks'' to implement C++ vtables. */
> > +/* Do not use ``thunks'' to implement C++ vtables. This method still has
> > + fatal bugs. */
> > #undef DEFAULT_VTABLE_THUNKS
> > -#define DEFAULT_VTABLE_THUNKS 1
>
> Is this disabled because it has bugs, or just because it is incompatible with
> the FreeBSD GCC's C++ ABI? If the latter, then the comment is misleading.
I'm surprised you don't know "DEFAULT_VTABLE_THUNKS 1" has *major* bugs.
The comment is on the mark. Ask H.J. Lu about it sometime.
When it got changed from `1' to `2', the bugs were supose to have been
fixed and thus provided a better C++ ABI than the native FreeBSD G++.
Now that "DEFAULT_VTABLE_THUNKS" went back to `1', it provides no
advanatge and is still a different C++ ABI than the native FreeBSD G++.
--
-- David (obrien@FreeBSD.org)