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Re: [PATCH] 2.95: turn off DEFAULT_VTABLE_THUNKS


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)


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