Why is this member function a duplicate?

Question

I have some code that's worked on VS10 and works on several other platforms, but causes a strange error on VS2015. The error (in a template expansion inside Boost) is very strange because it points to a form without const and tells me that it duplicates the previous member function immediately before it in the source, which is a variation that adds const.

Here is a minimal example I've managed to distill from the offending program.

#define BOOST_MULTI_INDEX_DISABLE_SERIALIZATION
#include "boost/multi_index_container.hpp"
#include "boost/multi_index/key_extractors.hpp"
#include "boost/multi_index/ordered_index.hpp"

class C1 { };

class  C2 {
public:
    uint32_t xx1;
    C1 f2() const;
};

namespace bmi = boost::multi_index;

typedef boost::multi_index_container<
    std::shared_ptr< const C2 >,
    bmi::indexed_by<
        bmi::ordered_unique<
            bmi::tag<C1>,
            bmi::composite_key<
                const C2,
                bmi::const_mem_fun< C2, C1, &C2::f2 >,
                bmi::member< C2, const uint32_t, &C2::xx1 >
            > // composite
        > // ordered_unique
    > // indexed_by
> BadContainerBase;

struct BadType : public BadContainerBase { };

I'm using VS2015 with x86 (32-bit) targeted.

The full error is:

E:\C++Libs\boost_1_59_0\boost/multi_index/composite_key.hpp(638): error C2535: 'boost::multi_index::composite_key_result<boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>> boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>::operator ()(const boost::reference_wrapper<const Class> &) const': member function already defined or declared
        with
        [
            Class=C2
        ]
E:\C++Libs\boost_1_59_0\boost/multi_index/composite_key.hpp(632): note: see declaration of 'boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>::operator ()'
E:\C++Libs\boost_1_59_0\boost/multi_index/detail/ord_index_args.hpp(46): note: see reference to class template instantiation 'boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>' being compiled
E:\C++Libs\boost_1_59_0\boost/mpl/eval_if.hpp(41): note: see reference to class template instantiation 'boost::multi_index::detail::index_args_default_compare<boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>>' being compiled
E:\C++Libs\boost_1_59_0\boost/multi_index/detail/ord_index_args.hpp(70): note: see reference to class template instantiation 'boost::mpl::eval_if<boost::mpl::is_na<boost::mpl::na>,boost::multi_index::detail::index_args_default_compare<boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>>,boost::mpl::identity<boost::mpl::na>>' being compiled
E:\C++Libs\boost_1_59_0\boost/multi_index/ordered_index.hpp(65): note: see reference to class template instantiation 'boost::multi_index::detail::ordered_index_args<Arg1,Arg2,Arg3>' being compiled
        with
        [
            Arg1=boost::multi_index::tag<C1,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,
            Arg2=boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>,
            Arg3=boost::mpl::na
        ]
E:\C++Libs\boost_1_59_0\boost/multi_index/detail/node_type.hpp(44): note: see reference to class template instantiation 'boost::multi_index::ordered_unique<boost::multi_index::tag<C1,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>,boost::mpl::na>' being compiled
E:\C++Libs\boost_1_59_0\boost/mpl/aux_/preprocessed/plain/apply_wrap.hpp(49): note: see reference to class template instantiation 'boost::multi_index::detail::index_node_applier::apply<T1,T2>' being compiled
        with
        [
            T1=boost::mpl::v_iter<boost::mpl::vector1<boost::multi_index::ordered_unique<boost::multi_index::tag<C1,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>,boost::mpl::na>>,0>,
            T2=boost::multi_index::detail::index_node_base<std::shared_ptr<const C2>,std::allocator<std::shared_ptr<const C2>>>
        ]
E:\C++Libs\boost_1_59_0\boost/mpl/aux_/preprocessed/plain/bind.hpp(207): note: see reference to class template instantiation 'boost::mpl::apply_wrap2<boost::multi_index::detail::index_node_applier,boost::mpl::v_iter<boost::mpl::vector1<T0>,0>,boost::multi_index::detail::index_node_base<Value,Allocator>>' being compiled
        with
        [
            T0=boost::multi_index::ordered_unique<boost::multi_index::tag<C1,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>,boost::mpl::na>,
            Value=std::shared_ptr<const C2>,
            Allocator=std::allocator<std::shared_ptr<const C2>>
        ]
E:\C++Libs\boost_1_59_0\boost/mpl/aux_/preprocessed/plain/apply_wrap.hpp(49): note: see reference to class template instantiation 'boost::mpl::bind2<boost::multi_index::detail::index_node_applier,boost::mpl::_2,boost::mpl::_  ::apply<T1,T2,boost::mpl::na,boost::mpl::na,boost::mpl::na>' being compiled
        with
        [
            T1=boost::multi_index::detail::index_node_base<std::shared_ptr<const C2>,std::allocator<std::shared_ptr<const C2>>>,
            T2=boost::mpl::v_iter<boost::mpl::vector1<boost::multi_index::ordered_unique<boost::multi_index::tag<C1,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>,boost::mpl::na>>,0>
        ]
E:\C++Libs\boost_1_59_0\boost/mpl/aux_/preprocessed/plain/apply.hpp(63): note: see reference to class template instantiation 'boost::mpl::apply_wrap2<boost::mpl::bind2<boost::multi_index::detail::index_node_applier,boost::mpl::_2,boost::mpl::_  ,T1,T2>' being compiled
        with
        [
            T1=boost::multi_index::detail::index_node_base<std::shared_ptr<const C2>,std::allocator<std::shared_ptr<const C2>>>,
            T2=boost::mpl::v_iter<boost::mpl::vector1<boost::multi_index::ordered_unique<boost::multi_index::tag<C1,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>,boost::mpl::na>>,0>
        ]
E:\C++Libs\boost_1_59_0\boost/mpl/aux_/preprocessed/plain/reverse_iter_fold_impl.hpp(58): note: see reference to class template instantiation 'boost::mpl::apply2<BackwardOp,boost::multi_index::detail::index_node_base<Value,Allocator>,boost::mpl::v_iter<boost::mpl::vector1<T0>,0>>' being compiled
        with
        [
            BackwardOp=boost::mpl::bind2<boost::multi_index::detail::index_node_applier,boost::mpl::_2,boost::mpl::_  ,
            Value=std::shared_ptr<const C2>,
            Allocator=std::allocator<std::shared_ptr<const C2>>,
            T0=boost::multi_index::ordered_unique<boost::multi_index::tag<C1,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>,boost::mpl::na>
        ]
E:\C++Libs\boost_1_59_0\boost/mpl/reverse_iter_fold.hpp(43): note: see reference to class template instantiation 'boost::mpl::aux::reverse_iter_fold_impl<1,boost::mpl::v_iter<boost::mpl::vector1<T0>,0>,boost::mpl::v_iter<boost::mpl::vector1<T0>,  ,State,boost::mpl::bind2<boost::multi_index::detail::index_node_applier,boost::mpl::_2,boost::mpl::_  ,boost::mpl::protect<boost::mpl::arg<  ,0>>' being compiled
        with
        [
            T0=boost::multi_index::ordered_unique<boost::multi_index::tag<C1,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>,boost::mpl::na>,
            State=boost::multi_index::detail::index_node_base<std::shared_ptr<const C2>,std::allocator<std::shared_ptr<const C2>>>
        ]
E:\C++Libs\boost_1_59_0\boost/multi_index/detail/node_type.hpp(57): note: see reference to class template instantiation 'boost::mpl::reverse_iter_fold<IndexSpecifierList,boost::multi_index::detail::index_node_base<Value,Allocator>,boost::mpl::bind2<boost::multi_index::detail::index_node_applier,boost::mpl::_2,boost::mpl::_  ,boost::mpl::arg<  >' being compiled
        with
        [
            IndexSpecifierList=boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::multi_index::tag<C1,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>,boost::mpl::na>,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,
            Value=std::shared_ptr<const C2>,
            Allocator=std::allocator<std::shared_ptr<const C2>>
        ]
E:\C++Libs\boost_1_59_0\boost/multi_index_container.hpp(89): note: see reference to class template instantiation 'boost::multi_index::detail::multi_index_node_type<Value,IndexSpecifierList,Allocator>' being compiled
        with
        [
            Value=std::shared_ptr<const C2>,
            IndexSpecifierList=boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::multi_index::tag<C1,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>,boost::mpl::na>,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,
            Allocator=std::allocator<std::shared_ptr<const C2>>
        ]
Annotation\Model.cpp(40): note: see reference to class template instantiation 'boost::multi_index::multi_index_container<std::shared_ptr<const C2>,boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::multi_index::tag<C1,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,boost::multi_index::composite_key<const C2,boost::multi_index::const_mem_fun<C2,C1,C1 C2::f2(void) const>,boost::multi_index::member<C2,const uint32_t,pointer-to-member(0x0)>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>,boost::mpl::na>,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na,boost::mpl::na>,std::allocator<Value>>' being compiled
        with
        [
            Value=std::shared_ptr<const C2>
        ]

Looking at the line it reports

// *** this earlier one has ⋯const C2>&⋯ where the error claims the problem lies.
result_type operator()(const reference_wrapper<const value_type>& x)const
{
  return result_type(*this,x.get());
}

result_type operator()(const reference_wrapper<value_type>& x)const
{   // *** error points to this line, and value_type is C2, and the template parameter is =not= const C2.
  return result_type(*this,x.get());
}

What's going on here? This seems to be an ordinary use of boost::multi_index_container.

score 3 · Accepted Answer · answered Dec 24 '15 at 10:26

3

Your composite_key is wrongly specified, it should be

bmi::composite_key<
    C2,
    bmi::const_mem_fun< C2, C1, &C2::f2 >,
    bmi::member< C2, const uint32_t, &C2::xx1 >
>

i.e. without the const qualifier in the first argument. Also, you might want to take a look at this section in Boost.MultiIndex docs, particularly the penultimate paragraph.

answered Dec 24 '15 at 10:26

Joaquín M López Muñoz

5,243
1
15
20

Interesting. Having `const C2` as the substitution for `value_type` would certainly make those declarations match. But the error message is telling me that it's just plain `C2` and I thought it had already been stripped down to basics in the bowels of the mpl stuff before getting to this point. For the paragraph in the docs you point out, `member` is what I have. – JDługosz Dec 25 '15 at 07:20
My redirecting you to that section of the docs sheds little light on the problem, sorry. Instead, please take a look at http://www.boost.org/libs/multi_index/doc/reference/key_extraction.html#composite_key , where you can see two overloads of `operator ()` on `const reference_wrapper&` and `const reference_wrapper&`, respectively, which implies `composite_key`is ill-defined if `value_type` is `const`. – Joaquín M López Muñoz Dec 25 '15 at 10:10
I will study that shortly, @Joaquin, thanks. I guess I don't understand why the compiler *isn't* showing `const C2` for the substituted type, which I agree would cause that problem. But I've not unraveled the expansions to see if it's indeed being invoked with C2 bare, and the compiler's just dropping it somewhere (even though it has no trouble showing const in other places). – JDługosz Dec 25 '15 at 10:15

Why is this member function a duplicate?

1 Answers1