Re: [cxx-abi-dev] Mangling of anonymous unions?

[Kerch Holt <kerch@xxxxxxxxxx>]

Jason Merrill wrote:
> On Wed, 18 Dec 2002 15:54:30 -0500, Jason Merrill <jason@xxxxxxxxxx> wrote:
>
>
> > I just noticed that the ABI doesn't define a mangling for anonymous
> > unions.  This is only really relevant for static local anonymous unions in
> > inline functions; all others are private to a translation unit.
> >
> > The choices would seem to be:
> >
> > 1) Use the name of the first member.
> > 2) Use the name of the largest member.
> > 3) Treat them like string literals, perhaps using 'u' instead of 's'.
> >
> > g++ currently does #2.  But it also fails to allocate space for such a
> > union (q.v. g++.brendan/union1.C), so there's no binary compatibility issue
> > in choosing a different answer.
> >
> > My order of preference is 3, 1, 2.  And yes, I'm volunteering to fix g++.
>
> After working on this for a bit, I like #3 much less; it doesn't work very
> well for namespace-scope unions, which we might as well mangle the same
> way.
Wouldn't you need some type of factoring of all the members of the union
(instead of first/last) to avoid collisions (of similar unions in the
same inline)?

BTW HP C++ is slightly broken WRT this feature -- so changing to meet
some other spec wouldn't cause too much pain.

--
Kerch Holt
HP Cupertino Language & Tools Lab