Re: [boost] [typeof]Typeof with MinGW

24 May 2007

      On 5/24/07, Peder Holt <peder.holt@gmail.com> wrote:
...
2007/5/24, Minmin Gong <gongminmin@yeah.net>:
[...]
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.
Well, vector has no 'type' type. Anyways, It fail)s for 'iterator' too:

   std::vector<int> v;
   typedef typeof(int)::iterator type;
...
Unfortunately there is little we can do to fix this in Boost.Typeof.
This works though (at least with gcc 4.1.2):

  #include <vector>

  template<typename T>
  struct identity {
    typedef T type;
  };

  int main() {
     std::vector<int> v;
     typedef identity<typeof(v)>::type::iterator type;
  }

So BOOST_TYPEOF could include 'identity' in its expansion.

It might fail with more complex expression as I heard that gcc doesn't
like much typeof in template parameters (but never tested it).

gpd

Re: [boost] [typeof]Typeof with MinGW

Giovanni Piero Deretta