Re: [boost] [1.33.0] VC 7.1 vs. SFINAE/type traits

From: Mat Marcus (mat-boost_at_[hidden])
Date: 2005-08-16 17:30:59

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The compilation errors are quite strange. For one thing, the compiler
is complaining that names of members of various classes in <sstream>
cannot be found. The code works against boost 1.32.0 and even against
1.33.0 with a (slightly modified) type traits folder from 1.32.0, but
fails against the full 1.33.0. I suspect that something changed with
the current release of the is_enum implementation that made the snippet
below unhappy on VC 7.1. I have been spending a good deal of time
trying to get to the bottom of this, so thanks for your interest. The
intent of the code is to SFINAE-conditionally provide a family of
operators for enums.

In any case, here are two sample error messages (_Mystate is a member
of basic_stringbuf)

 - Mat

c:\Program Files\Microsoft Visual Studio .NET
2003\Vc7\include\sstream(267) : error C2065: '_Mystate' : undeclared
identifier
        c:\Program Files\Microsoft Visual Studio .NET
2003\Vc7\include\sstream(265) : while compiling class-template member
functi
on 'void std::basic_stringbuf<_Elem,_Traits,_Alloc>::_Init(const _Elem
*,size_t,std::basic_stringbuf<_Elem,_Traits,_Alloc>::_Strst
ate)'
        with
        [
            _Elem=char,
            _Traits=std::char_traits<char>,
            _Alloc=std::allocator<char>
        ]
        c:\Program Files\Microsoft Visual Studio .NET
2003\Vc7\include\sstream(503) : see reference to class template
instantiatio
n 'std::basic_stringbuf<_Elem,_Traits,_Alloc>' being compiled
        with
        [
            _Elem=char,
            _Traits=std::char_traits<char>,
            _Alloc=std::allocator<char>
        ]
        adobe\future\widgets\headers\report_exception.hpp(56) : see
reference to class template instantiation 'std::basic_stringst
ream<_Elem,_Traits,_Alloc>' being compiled
        with
        [
            _Elem=char,
            _Traits=std::char_traits<char>,
            _Alloc=std::allocator<char>
        ]

Followed by this and others:

third_party\boost_tp\boost\boost\type_traits\is_convertible.hpp(202) :
error C2668: 'boost::detail::is_convertible_basic_impl<From
,To>::_m_check' : ambiguous call to overloaded function
        with
        [

From=boost::detail::is_convertible_impl<boost::add_reference<'unknown-type'>::type
,boost::detail::int_convertible>::r
ef_type,
            To=boost::detail::int_convertible
        ]

third_party\boost_tp\boost\boost\type_traits\is_convertible.hpp(199):
could be 'boost::type_traits::yes_type boost::detail
::is_convertible_basic_impl<From,To>::_m_check(To)'
        with
        [

From=boost::detail::is_convertible_impl<boost::add_reference<'unknown-type'>::type
,boost::detail::int_convertible>::r
ef_type,
            To=boost::detail::int_convertible
        ]

third_party\boost_tp\boost\boost\type_traits\is_convertible.hpp(198):
or       'boost::type_traits::no_type boost::detail:
:is_convertible_basic_impl<From,To>::_m_check(...)'
        with
        [

From=boost::detail::is_convertible_impl<boost::add_reference<'unknown-type'>::type
,boost::detail::int_convertible>::r
ef_type,
            To=boost::detail::int_convertible
        ]
        while trying to match the argument list '('unknown-type')'

third_party\boost_tp\boost\boost\type_traits\is_convertible.hpp(228) :
see reference to class template instantiation 'boos
t::detail::is_convertible_basic_impl<From,To>' being compiled
        with
        [

From=boost::detail::is_convertible_impl<boost::add_reference<'unknown-type'>::type
,boost::detail::int_convertible>::r
ef_type,
            To=boost::detail::int_convertible
        ]

third_party\boost_tp\boost\boost\type_traits\is_convertible.hpp(302) :
see reference to class template instantiation 'boos
t::detail::is_convertible_impl<From,To>' being compiled
        with
        [
            From=boost::add_reference<'unknown-type'>::type ,
            To=boost::detail::int_convertible
        ]

third_party\boost_tp\boost\boost\type_traits\is_convertible.hpp(348) :
see reference to class template instantiation 'boos
t::detail::is_convertible_impl_dispatch<From,To>' being compiled
        with
        [
            From=boost::add_reference<'unknown-type'>::type ,
            To=boost::detail::int_convertible
        ]
        third_party\boost_tp\boost\boost\type_traits\is_enum.hpp(96) :
see reference to class template instantiation 'boost::is_co
nvertible<From,To>' being compiled
        with
        [
            From=boost::add_reference<'unknown-type'>::type,
            To=boost::detail::int_convertible
        ]
        third_party\boost_tp\boost\boost\type_traits\is_enum.hpp(153) :
see reference to class template instantiation 'boost::deta
il::is_enum_helper<false>::type<T>' being compiled
        with
        [
            T='unknown-type'
        ]
        third_party\boost_tp\boost\boost\type_traits\is_enum.hpp(166) :
see reference to class template instantiation 'boost::deta
il::is_enum_impl<T>' being compiled
        with
        [
            T='unknown-type'
        ]
        third_party\boost_tp\boost\boost\utility\enable_if.hpp(36) :
see reference to class template instantiation 'boost::is_enum
<T>' being compiled
        with
        [
            T='unknown-type'
        ]
        c:\Program Files\Microsoft Visual Studio .NET
2003\Vc7\include\sstream(270) : see reference to class template
instantiatio
n 'boost::enable_if<Cond,T>' being compiled
        with
        [
            Cond=boost::is_enum<'unknown-type'>,
            T='unknown-type'
        ]

- --On Tuesday, August 16, 2005 8:15 AM -0700 Mat Marcus
<mat-boost_at_[hidden]> wrote:

> In one of our projects, the following code produces some strange
> compilation errors under VC 7.1/boost 1.33.0. Can anyone suggest a
> workaround?
> 
>  - Mat
> 
># include <sstream>
># include "boost/type_traits.hpp"
># include "boost/utility/enable_if.hpp"
> 
> template <typename EnumType>
> typename boost::enable_if<boost::is_enum<EnumType>, EnumType>::type 
> operator ~ (EnumType a);
> 
> std::stringstream t;
> 
>  

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