In article <37laceF5e4e9sU1@[EMAIL PROTECTED]
>,
"Jonathan Turkanis" <technews@[EMAIL PROTECTED]
> wrote:
> Hi,
>
> This is essentially a re-post of a message from a few days ago, with a
more
> eye-catching subject line.
>
> According to section 13.6 of the standard, an operator of the form
>
> T& operator*(T*)
>
> should be considered during overload resolution for an expression of the
form
> *x
> where x has class type, only if T is a function type or an object type.
Since
> void is not an object type, the no operator of the form operator*(void*)
> should
> be considered.
>
> However, I'm getting a complaint of ambiguity from Codewarrior 9.3 and
9.4
> relating to an expression *x, where x has type std::istream, in which
one of
> the
> two candidate functions is described as operator*(void*). (See
> http://tinyurl.com/626kr).
>
> The following test program is a simplification of the code which leads
to the
> above error.
>
> struct Thing {
> operator void* () const;
> };
>
> struct any {
> template<class T>
> any(T const&);
> };
>
> char operator*(any const&);
>
> int main()
> {
> Thing t;
> *t;
> }
>
> Any help would be greatly appreciated.
Jonathan, thank you very much for the concise bug re****t. Our apologies
for not getting back to you sooner. This has been forwarded to our chief
compiler engineer, and fixed for the next release.
In the meantime, as a workaround, the only thing I'm coming up with is
to check is_convertible<T, void*> before proceeding with the
is_dereferenceable check. I realize this is kind of a hack. But
perhaps it is better than the status quo.
Maybe something along the lines of:
#include <msl_utility>
struct any {
template<class T>
any(T const&);
};
char operator*(any const&);
struct two {char dummy_[2];};
namespace detail
{
template <class T>
class is_dereferenceable
{
static typename
Metrowerks::select<Metrowerks::is_fundamental<T>::value,
any, T&>::type t;
template <class U> static char test(const U&);
template <class U> static two test(char);
public:
static const bool value = sizeof(test<T>(*t)) == 1;
};
} // detail
template <class T>
class is_dereferenceable
{
template <class U> static char test(const U&);
template <class U> static two test(char);
public:
static const bool value = Metrowerks::_and<
Metrowerks::_not<Metrowerks::is_convertible<T, void*> >,
detail::is_dereferenceable<T> >::value;
};
Thanks again for the bug re****t, your perseverance, and your patience.
-Howard
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