[cxx-abi-dev] Re: C++ ABI: Reuse of tail padding

[Jim Dehnert]

Nathan Sidwell wrote:
> 
> Mark Mitchell wrote:
> 
> > We have a problem here.
> 
> > Intel's compiler does not pack things into the tail padding.
> > Neither, I expect, does HP's.
> I would like to get hard data from more than the two compilers
> you've verified.
> 
> > Technically, the G++ version is superior.  (It reduces space used by
> > objects.)  On the other hand, it was basically impossible for
> > implementors to figure out what was intended from the spec.
> >
> > I think I would prefer to change G++, and drop this idea from the spec,
> > even though it is an optimization.
>
> Although using tail padding is neat, how many bytes would it
> save in real programs? You only get it with structs of the form
>         int i;
>         char c;
> or (on some non-i86 machines)
>         double d;
>         int i;

That's true.  We did, however, have people during the meetings (I
don't recall who) who felt strongly about reusing the tail padding as
suggested.  It was intended to be done that way -- I apologize for not
making it clearer in the writeup.

Jim

-- 
-	    Jim Dehnert		dehnert at transmeta.com
	    (408)919-6984	dehnertj at acm.org