[Boost-bugs] [Boost C++ Libraries] #9647: boost_MPL_ASSERT_RELATION fails to properly handle unsigned types

Subject: [Boost-bugs] [Boost C++ Libraries] #9647: boost_MPL_ASSERT_RELATION fails to properly handle unsigned types
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-02-09 21:00:37

#9647: boost_MPL_ASSERT_RELATION fails to properly handle unsigned types
------------------------------+----------------------
 Reporter:  ramey             |      Owner:  dlwalker
     Type:  Bugs              |     Status:  new
Milestone:  To Be Determined  |  Component:  integer
  Version:  Boost 1.54.0      |   Severity:  Problem
 Keywords:                    |
------------------------------+----------------------
 boost/integer_traits.hpp contains the following
 {{{
 template<>
 class integer_traits<unsigned long>
   : public std::numeric_limits<unsigned long>,
     public detail::integer_traits_base<unsigned long, 0, ULONG_MAX>
 { };
 }}}

 Problem is that, at least on Clang ULONG_MAX resolves to (through
 <limits.h>) to be

 {{{
 #define ULONG_MAX (__LONG_MAX__ *2UL+1UL)
 }}}

 But when __LONG_MAX__ resolves to long and the rules of arithmetic
 promotion result in the expression
 __LONG_MAX__ *2UL+1UL being a long rather than unsigned long. This causes
 some funky behavior in cases like:

 {{{
 BOOST_MPL_ASSERT_RELATION(
     (boost::integer_traits<unsigned long>::const_max),
     >,
     (boost::integer_traits<unsigned char>::const_max)
 );
 }}}

 which fails to compile with "Non-type template argument evaluates to
 4294967295, which cannot be narrowed to type 'long'

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/9647>
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