[boost] Microsoft compiler(s) bug? Was: Formal Review: Typeof

From: Arkadiy Vertleyb (vertleyb_at_[hidden])
Date: 2005-05-21 08:20:57

"Arkadiy Vertleyb" <vertleyb_at_[hidden]> wrote in message

> "David Abrahams" <dave_at_[hidden]> wrote
>
> > Unfortunately there are still problems with vc-8:
> >
> > ..\..\..\..\boost/sequence/detail/typeof_add.hpp(15) : error C2893:
Failed
> to specialize function template 'char (&boost::type_of::size(const T
>
&))[boost::mpl::size<encode_type<boost::type_of::vector0<>,T>::type>::value]
> '
> >         With the following template arguments:
> >         'T'
> >         ..\..\..\..\boost/sequence/detail/typeof_add.hpp(16) : see
> reference to class template instantiation
> 'boost::sequence::detail::typeof_add<T,U>' being compiled
> >
> > See the updated archive.
>
> I've run into this problem before.  Looks like it's present only in vc8
> beta.  Seems to be "fixed" if make<T>() is replaced with T() -- of course
> then we have problems with non-default-constructible classes.  *(T*)0
> doesn't work either.
>
> Doesn't look like a Typeof problem, although Typeof may be responsible for
> driving the compiler crazy, after which it chokes.
>
> Seems to be a question to Microsoft...

After looking at this more closely, I believe the problem can't always be
"cured" in the way I suggested.  Also it can be reproduced on both vc71 and
vc8 beta.  Here is the minimal example:

// ----
#include "boost/mpl/vector.hpp"
#include "boost/mpl/size_t.hpp"

template<class T> T make();

template<class T>
struct et
{
    typedef boost::mpl::vector1<int> type;
};

template<class T>
char(&sz(const T&))[
    boost::mpl::size<
        typename et<T>::type
    >::value
];

template<class T, class U>
struct add
{
    typedef boost::mpl::vector1<
        boost::mpl::size_t<sizeof(sz(make<T>() + make<U>()))>
        //boost::mpl::size_t<sizeof(sz(T() + U()))> -- doesn't help here
    > type;
};

int main()
{
    return 0;
}
// ----

This example compiles fine with GCC, but both MS compilers choke on it.

OTOH, our ODR test uses BOOST_TYPEOF_TPL(T() + U()) in a few different
contexts, and it works fine on both MS compilers.

Do Microsoft people read this list, or should I post it elsewhere?

Regards,
Arkadiy