id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
9647	BOOST_MPL_ASSERT_RELATION fails to properly handle unsigned types	Robert Ramey	Aleksey Gurtovoy	"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'"	Bugs	new	To Be Determined	mpl	Boost 1.54.0	Problem