[cxx-abi-dev] Passing non-trivial types through ...

[Dennis Handly]

>From: John McCall <rjmccall at apple.com>
>I’d be happier if you disavowed the previous implementation of the
>extension, of course. :)

Well, that's what "undefined" means.  :-)

>So, you suppress destruction completely of the argument, and it potentially
>goes undestructed?

Yes, and since we don't call the copy constructor, everything is balanced.

>I don’t see how we can prevent it
John.

You just say that this use of va_arg produces a const Foo& and don't allow
Foo to be mentioned.  I suppose you could allow a "const Foo" too.

With your current idea, did you plan to invoke copy constructor or copy
assignment operator for:
   Foo f = va_arg(ap, Foo);

I would assume you would have to do that, since the user can "rewind" and
use va_start ... va_end multiple times.