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

On Fri, Apr 13, 2012 at 8:02 AM, John M. Dlugosz 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 #include "boost/thread/future.hpp" #include #include <functional>

using boost::unique_future;

template <typename F> unique_future::type> foo (F&& f) { typedef typename boost::result_of< F() >::type RetType; unique_future<RetType> future_result; return std::move(future_result); }

template unique_future::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' 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' 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::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::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