Re: [boost] [mpl] strange vector_c and integral_c construction

Subject: Re: [boost] [mpl] strange vector_c and integral_c construction
From: Dmitry Goncharov (dgoncharov_at_[hidden])
Date: 2009-08-12 03:58:46

Maxim Yanchenko wrote:
> Hi all,
>   
> Probably this is well-known and I just failed to find it in the docs and mailing
> list.
>
> According to the docs
> (http://www.boost.org/doc/libs/1_39_0/libs/mpl/doc/refmanual/integral-sequence-wrapper.html):
>
>   typedef seq_c<T,c1,c2,... cn> s;
>   Semantics:	s is a sequence seq of integral constant wrappers integral_c<T,c1>,
> integral_c<T,c2>, ... integral_c<T,cn>.
>
>
>
> Consider the following example:
>   
>   const int64_t max_int         = integer_traits<int>::const_max;
>   const int64_t max_int_plus_1  = max_int + 1;
>   
>   BOOST_MPL_ASSERT(( equal<           vector_c< int64_t, 1 >
>                           , vector< integral_c< int64_t, 1 > >
>                           > ));
>
>   BOOST_MPL_ASSERT(( equal<           vector_c< int64_t, max_int >
>                           , vector< integral_c< int64_t, max_int > >
>                           > ));
>
>   BOOST_MPL_ASSERT(( equal<           vector_c< int64_t, max_int_plus_1 >
>                           , vector< integral_c< int64_t, max_int_plus_1 > >
>                           > ));
>
> The first assert passes, while the second and third fail with the following
> error messages (removed repetition of 2147483647l for readability):
> test.h:149: error: ************mpl::equal<mpl::vector_c<int64_t, 2147483647l,
> 2147483647l, ...>, mpl::vector<mpl_::integral_c<int64_t, 2147483647>>,
> is_same<true> >::************'
> test.h:153: error: ************mpl::equal<mpl::vector_c<int64_t,
> -0x00000000080000000l, 2147483647l, ...>, mpl::vector<mpl_::integral_c<int64_t,
> 2147483648ll>>, is_same<true> >::************'
>
> I consider these errors as a contradiction to the docs statement.
> Probably, I configured MPL wrong, as I see in the preprocessed code, where long
> is used (boost/mpl/aux_/preprocessed/gcc/vector_c.hpp)
>
> template<
>       typename T, long C0 = LONG_MAX, long C1 = LONG_MAX, long C2 = LONG_MAX
>     , long C3 = LONG_MAX, long C4 = LONG_MAX, long C5 = LONG_MAX
>     , long C6 = LONG_MAX, long C7 = LONG_MAX, long C8 = LONG_MAX
>     , long C9 = LONG_MAX, long C10 = LONG_MAX, long C11 = LONG_MAX
>     , long C12 = LONG_MAX, long C13 = LONG_MAX, long C14 = LONG_MAX
>     , long C15 = LONG_MAX, long C16 = LONG_MAX, long C17 = LONG_MAX
>     , long C18 = LONG_MAX, long C19 = LONG_MAX
>     >
> struct vector_c;
>
> I'm using GCC 3.4.6, on Linux-64, compiling 32-bit binary (so int and long are
> of same size, and boost::int64_t is bigger than long).
>
> Thanks, 
> Maxim (to reply in private, please use FirstName.LastName at gmail.com)
>
>   
gcc-4.3.3 and 4.4.0 compile this example fine.

BR, Dmitry