Re: [Boost-users] Compiler craziness on boost::result_of ? Please help

Subject: Re: [Boost-users] Compiler craziness on boost::result_of ? Please help
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 2012-04-13 12:33:14

On Fri, Apr 13, 2012 at 8:02 AM, John M. Dlugosz <mpbecey7gu_at_[hidden]>wrote:

> I'm using Visual Studio 10, and Boost 1.49.  The following complete CPP
> file compiles without error:
>

I don't have access to VS 10 so...bear with me...

> =====
> #include <boost/test/unit_test.hpp>
> #include "boost/thread/future.hpp"
> #include <boost/utility/result_of.hpp>
> #include <functional>
>
> using boost::unique_future;
>
> template <typename F>
> unique_future<typename boost::result_of< F() >::type>
> foo (F&& f)
>  {
>  typedef typename boost::result_of< F() >::type RetType;
>  unique_future<RetType> future_result;
>  return std::move(future_result);
>  }
>
> template <typename F, typename A1>
> unique_future<typename boost::result_of< F(A1) >::type>
> foo (F&& f, A1&& a1)
>  {
>  return std::move(foo (std::tr1::bind(f,a1)));
>  }
>
>
>
> class C {};
>
> class D  : public C {
> public:
>   void mf() const  { }
> //   virtual void toxic()  { }
>   };
>
>
> void mainfunc()
> {
>
>    D* p;
>    foo (&D::mf, p);
>
> }
>
> =====
>
> But, if you un-comment the definition of toxic, then it will not compile,
> giving instead:
>
> 1>E:\boost_1_49\boost/utility/**result_of.hpp(82): error C2825: 'F': must
> be a class or namespace when followed by '::'
> 1>          E:\boost_1_49\boost/utility/**result_of.hpp(90) : see
> reference to class template instantiation 'boost::detail::result_of_**nested_result<F,FArgs>'
> being compiled
> 1>          with
> 1>          [
> 1>              F=void (__thiscall D::* &)(void) const,
>

Hmmm...I wonder if the problem is that F is bound to a *reference* to a
pointer-to-member. Although then I'm surprised things work without the base
class or the virtual member function.

Try replacing "F" in your boost::result_of queries with
boost::remove_reference<F>::type.

> 1>              FArgs=void (__thiscall D::* &(D *&))(void) const
> 1>          ]
> 1>          E:\boost_1_49\boost/utility/**detail/result_of_iterate.hpp(**33)
> : see reference to class template instantiation
> 'boost::detail::tr1_result_of_**impl<F,FArgs,HasResultType>' being
> compiled
> 1>          with
> 1>          [
> 1>              F=void (__thiscall D::* &)(void) const,
> 1>              FArgs=void (__thiscall D::* &(D *&))(void) const,
> 1>              HasResultType=false
> 1>          ]
>

Also, see if changing line 25 in result_of_iterate.hpp (near the reference
above) to

          mpl::or_< is_pointer< typename boost::remove_reference<F>::type
>, is_member_function_pointer< typename boost::remove_reference<F>::type > >

from

          mpl::or_< is_pointer<F>, is_member_function_pointer<F> >

helps.

1>          E:\boost_1_49\boost/utility/**detail/result_of_iterate.hpp(**75)
> : see reference to class template instantiation 'boost::tr1_result_of<F>'
> being compiled
> 1>          with
> 1>          [
> 1>              F=void (__thiscall D::* &(D *&))(void) const
> 1>          ]
> 1>          threadpoolTest.cpp(39) : see reference to class template
> instantiation 'boost::result_of<F>' being compiled
> 1>          with
> 1>          [
> 1>              F=void (__thiscall D::* &(D *&))(void) const
> 1>          ]
> 1>E:\boost_1_49\boost/utility/**result_of.hpp(82): error C2516: 'F' : is
> not a legal base class
> 1>          E:\boost_1_49\boost/utility/**result_of.hpp(90) : see
> declaration of 'F'
> 1>E:\boost_1_49\boost/utility/**result_of.hpp(82): error C2143: syntax
> error : missing ',' before '::'
> 1>E:\boost_1_49\boost/utility/**result_of.hpp(82): error C2903: 'result'
> : symbol is neither a class template nor a function template
> 1>E:\boost_1_49\boost/utility/**result_of.hpp(82): error C2039: 'result'
> : is not a member of '`global namespace''
> 1>E:\boost_1_49\boost/utility/**result_of.hpp(82): error C2504: 'result'
> : base class undefined
> 1>E:\boost_1_49\boost/utility/**result_of.hpp(82): error C2143: syntax
> error : missing ',' before '<'
> 1>threadpoolTest.cpp(39): error C2893: Failed to specialize function
> template 'boost::unique_future<boost::**result_of<F(T0)>::type> foo(F
> &&,A1 &&)'
> 1>          With the following template arguments:
> 1>          'void (__thiscall D::* &)(void) const'
> 1>          'D *&'
> 1>threadpoolTest.cpp(39): error C2780: 'boost::unique_future<boost::**result_of<F(void)>::type>
> foo(F &&)' : expects 1 arguments - 2 provided
> 1>          threadpoolTest.cpp(10) : see declaration of 'foo'
> 1>
> 1>Build FAILED.
>
>
> Note that both the presence of a virtual function and a base class in
> necessary.  if toxic is present but C is not, then it still works.
>

Again, this seems mysterious to me...

- Jeff