[Boost-users] Visual C++ 2005 error C2666 with variants.

From: Bill McLean (bill_at_[hidden])
Date: 2008-08-11 23:39:07

I have spent a couple of hours trying to resolve the following error when
building our system.  We have some code that has been compiling and working
with GCC with no issues. However building it with MS VC20005 SP1 creates the
following error. We are using boost 1.34.1:

 

Error      2              error C2666:
'boost::variant<T0_,T1,T2,T3,T4,T5,T6,T7>::convert_construct' : 2 overloads
have similar conversions
c:\projects\ardev\currentdev\externallibs\boost\boost\variant\variant.hpp
1342

 

I have searched the Boost list archives and found this post for boost
1.33.1:

 

http://lists.boost.org/Archives/boost/2006/03/102375.php

 

The author of this post Peter Schreegle did not receive a reply. He attached
the below code and build log. It appears that this an issue for variants
under visual studio 2005 SP1.  Does anyone know if this is an issue for VS
2008? Is this issue for boost 1.35.0 being built by VS 2005 or VS 2008?

#include <boost/variant.hpp> 

typedef boost::variant<char, int, double> numeric_type_variant; 

class numeric_type 
        : public numeric_type_variant 
{ 
public: 
        /// Default constructor. 
        numeric_type() : numeric_type_variant() { } 

        template <typename T> 
        /// Converting constructor. 
        numeric_type(T const& t) : numeric_type_variant(t) { } 

        // some more code 
}; 

int main(int argc, char* argv[]) 
{ 
        char ba; 
        int bb; 
        double bc; 

        numeric_type a; 
        numeric_type b(ba); 
        numeric_type c(bb); 
        numeric_type d(bc); 

        a = ba; 
        a = bb; 
        a = bc; 

        return 0; 
} 

************************************************************* 

This is the build log: 

------ Build started: Project: test_variant, Configuration: Debug Win32 
------ Compiling... 
test_variant.cpp 
c:\_ngi\toolkits\boost_1_33_1\boost\variant\variant.hpp(1342) : error C2666:

'boost::variant<T0_,T1,T2>::convert_construct' : 2 overloads have similar 
conversions 
        with 
        [ 
            T0_=char, 
            T1=int, 
            T2=double 
        ] 
        c:\_ngi\toolkits\boost_1_33_1\boost\variant\variant.hpp(1327): could

be 'void 
boost::variant<T0_,T1,T2>::convert_construct<char,int,double,boost::detail::

variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,b

oost::detail::variant::void_,boost::detail::variant::void_,boost::detail::va

riant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boo

st::detail::variant::void_,boost::detail::variant::void_,boost::detail::vari

ant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost

::detail::variant::void_,boost::detail::variant::void_,boost::detail::varian

t::void_,boost::detail::variant::void_>(const boost::variant<T0_,T1,T2> 
&,long)' 
        with 
        [ 
            T0_=char, 
            T1=int, 
            T2=double 
        ] 
        c:\_ngi\toolkits\boost_1_33_1\boost\variant\variant.hpp(1258): or 
'void boost::variant<T0_,T1,T2>::convert_construct<const T>(T 
&,int,boost::mpl::false_)' 
        with 
        [ 
            T0_=char, 
            T1=int, 
            T2=double, 
            T=numeric_type 
        ] 
        while trying to match the argument list '(const numeric_type, long)'

        c:\_ngi\toolkits\boost_1_33_1\boost\variant\variant.hpp(1580) : see 
reference to function template instantiation 
'boost::variant<T0_,T1,T2>::variant<T>(const T &)' being compiled 
        with 
        [ 
            T0_=char, 
            T1=int, 
            T2=double, 
            T=numeric_type 
        ] 
        c:\_ngi\toolkits\boost_1_33_1\boost\variant\variant.hpp(1590) : see 
reference to function template instantiation 'void 
boost::variant<T0_,T1,T2>::assign<T>(const T &)' being compiled 
        with 
        [ 
            T0_=char, 
            T1=int, 
            T2=double, 
            T=numeric_type 
        ] 
        c:\_schrott\test_variant\test_variant\test_variant.cpp(36) : see 
reference to function template instantiation 'boost::variant<T0_,T1,T2> 
&boost::variant<T0_,T1,T2>::operator =<numeric_type>(const T &)' being 
compiled 
        with 
        [ 
            T0_=char, 
            T1=int, 
            T2=double, 
            T=numeric_type 
        ] 
Build log was saved at 
"file://c:\_schrott\test_variant\test_variant\Debug\BuildLog.htm" 
test_variant - 1 error(s), 0 warning(s) 
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========