From: Arkadiy Vertleyb (vertleyb_at_[hidden])
Date: 2005-09-01 10:53:16
"David Abrahams" <dave_at_[hidden]> wrote
> Peder Holt <peder.holt_at_[hidden]> writes:
> > On 9/1/05, David Abrahams <dave_at_[hidden]> wrote:
> >> Eric Niebler <eric_at_[hidden]> writes:
> >> > Ah. But the fact remains that remove_pointer et al. are indeed broken
> >> > VC6 and VC7, and the regression tests bear this out.
> >> >
> >> > http://tinyurl.com/8fs7w
> >> >
> >> > IMO, the best path is to preserve the meaning of
> >> > BOOST_BROKEN_COMPILER_TYPE_TRAITS_SPECIALIZATION for compilers
> >> > PTS. That is, it still defines full specializations of the type
> >> > templates. But the typeof implementation should be what the primary
> >> > template uses for compilers without PTS. That way, everything that is
> >> > working now, keeps working with no change in performance.
> >> I think it would better to do some actual speed testing there. After
> >> all, using the typeof hack *could* turn out to be much faster and use
> >> fewer resources than doing it the other way.
> >> It's a pretty easy test.
> > I don't think using the typeof library directly is the best idea. When
> > using typeof, you represent each type by a number, limiting you to
> > ~1000 types.
> I hope that's false, but in any case, you've completely missed the
> point. There's a bugfeature in vc <= 7.1 that allows typeof to be
> implemented without any such limitation. No numerical representation
> is ever generated.
I think Peder is right. IIRC, when Igor Chesnokov invented the trick, it
needed __if_exist compiler extension on VC7. Peder got rid of it using
compile-time variables (discussed on this list about a year ago). I think
these compile-time variables are used to "register" types on the fly, at the
moment typeof gets invoked. And they are the ones that introduce this
I am not sure if the same limitation applies to VC6. I am also not
completely sure whether it applies to both VC70 and VC71 or to VC71 only...
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk