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Pick the first type that has the right alignment. The types are roughly ordered

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based on size, so this prevents the alignment type from being much larger than
it should be.


[SVN r18258]
This commit is contained in:
Douglas Gregor
2003-04-16 13:36:07 +00:00
parent a7321a4260
commit f9b5fa44f4
1 changed files with 13 additions and 13 deletions
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26
include/boost/type_traits/type_with_alignment.hpp
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@@ -1,8 +1,8 @@
// (C) Copyright John Maddock 2000.
// Permission to copy, use, modify, sell and distribute this software is
// granted provided this copyright notice appears in all copies. This
// software is provided "as is" without express or implied warranty,
// Permission to copy, use, modify, sell and distribute this software is
// granted provided this copyright notice appears in all copies. This
// software is provided "as is" without express or implied warranty,
// and with no claim as to its suitability for any purpose.
#ifndef BOOST_TT_TYPE_WITH_ALIGNMENT_INCLUDED
@@ -43,15 +43,20 @@ typedef int (alignment_dummy::*member_function_ptr)();
char, short, int, long, float, double, long double \
, void*, function_ptr, member_ptr, member_function_ptr))
#define BOOST_TT_CHOOSE_MIN_ALIGNMENT(R,P,I,T) \
typename mpl::if_c< \
alignment_of<T>::value <= target, T, char>::type BOOST_PP_CAT(t,I);
#define BOOST_TT_CHOOSE_MIN_ALIGNMENT(R,P,I,T) \
typename mpl::if_c< \
(alignment_of<T>::value == target && !BOOST_PP_CAT(found,I)), \
T, char>::type BOOST_PP_CAT(t,I); \
enum { BOOST_PP_CAT(found,BOOST_PP_INC(I)) = \
alignment_of<T>::value == target || BOOST_PP_CAT(found,I) } ;
#define BOOST_TT_CHOOSE_T(R,P,I,T) T BOOST_PP_CAT(t,I);
template <std::size_t target>
union lower_alignment
{
enum { found0 = false };
BOOST_PP_LIST_FOR_EACH_I(
BOOST_TT_CHOOSE_MIN_ALIGNMENT
, ignored
@@ -92,7 +97,7 @@ BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::detail::lower_alignment<32> ,
} // namespace detail
// This alignment method originally due to Brian Parker, implemented by David
// Abrahams, and then ported here by Doug Gregor.
// Abrahams, and then ported here by Doug Gregor.
template <int Align>
class type_with_alignment
{
@@ -105,13 +110,8 @@ class type_with_alignment
BOOST_STATIC_CONSTANT(std::size_t, found = alignment_of<align_t>::value);
#ifndef __BORLANDC__
BOOST_STATIC_ASSERT(found >= Align);
BOOST_STATIC_ASSERT(found % Align == 0);
#else
BOOST_STATIC_ASSERT(::boost::type_with_alignment<Align>::found >= Align);
BOOST_STATIC_ASSERT(::boost::type_with_alignment<Align>::found % Align == 0);
#endif
public:
typedef align_t type;