Re: [boost] [typeof]Typeof with MinGW

From: Peder Holt (peder.holt_at_[hidden])
Date: 2007-05-24 08:35:22

2007/5/24, Minmin Gong <gongminmin_at_[hidden]>:
> Hi all.
> Does Boost.Typeof work with MinGW in a little complex situation? I test
> it with this:
>
> #include <boost/typeof/typeof.hpp>
> #include <vector>
>
> using namespace std;
>
> int main()
> {
>         std::vector<int> v;
>         BOOST_TYPEOF(v)::value_type i;
> }
>
> It failed. But if the line 9 is changed from
> BOOST_TYPEOF(v)::value_type i;
> to
> typedef BOOST_TYPEOF(v) v_type;
> v_type::value_type i;
> It works.
>
> My question is why BOOST_TYPEOF(v)::value_type is not supported?
> I'm using MinGW with gcc 4.1.2. (3.4.2 fails too. But vc8 is OK.)
> Thanks.

On GCC we use the native typeof mechanism, so your code is actually
translated into this:

int main() {
    std::vector<int> v;
    typedef typeof(boost::type_of::ensure_obj(v))::type type;
}

The simpler:
typedef typeof(v)::type type;

fails to compile as well, so this is a shortcomming in the compiler.
Unfortunately there is little we can do to fix this in Boost.Typeof.

Regards,
Peder

>
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