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Replace some usage of std::forward to static_cast.

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For more details, See inline comment of include/boost/fusion/support/config.hpp .
This commit is contained in:
Kohei Takahashi
2014-11-25 22:23:55 +09:00
parent 687668c110
commit 9ab7774fd7
15 changed files with 61 additions and 32 deletions
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29
include/boost/fusion/support/config.hpp
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@@ -9,6 +9,7 @@
#define FUSION_SUPPORT_CONFIG_01092014_1718
#include <boost/config.hpp>
#include <boost/detail/workaround.hpp>
#ifndef BOOST_FUSION_GPU_ENABLED
#define BOOST_FUSION_GPU_ENABLED BOOST_GPU_ENABLED
@@ -39,4 +40,32 @@ namespace boost { namespace fusion { namespace detail
#define BOOST_FUSION_BARRIER_BEGIN namespace barrier {
#define BOOST_FUSION_BARRIER_END }
#if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1900))
// All of rvalue-reference ready MSVC don't perform implicit conversion from
// fundamental type to rvalue-reference of another fundamental type [1].
//
// Following example doesn't compile
//
// int i;
// long &&l = i; // sigh..., std::forward<long&&>(i) also fail.
//
// however, following one will work.
//
// int i;
// long &&l = static_cast<long &&>(i);
//
// OK, now can we replace all usage of std::forward to static_cast? -- I say NO!
// All of rvalue-reference ready Clang doesn't compile above static_cast usage [2], sigh...
//
// References:
// 1. https://connect.microsoft.com/VisualStudio/feedback/details/1037806/implicit-conversion-doesnt-perform-for-fund
// 2. http://llvm.org/bugs/show_bug.cgi?id=19917
//
// Tentatively, we use static_cast to forward if run under MSVC.
# define BOOST_FUSION_FWD_ELEM(type, value) static_cast<type&&>(value)
#else
# define BOOST_FUSION_FWD_ELEM(type, value) std::forward<type>(value)
#endif
#endif

6
include/boost/fusion/support/pair.hpp
View File

@@ -41,7 +41,7 @@ namespace boost { namespace fusion
BOOST_FUSION_GPU_ENABLED
pair(pair&& rhs)
: second(std::forward<Second>(rhs.second)) {}
: second(BOOST_FUSION_FWD_ELEM(Second, rhs.second)) {}
#endif
@@ -56,7 +56,7 @@ namespace boost { namespace fusion
pair(Second2&& val
, typename boost::disable_if<is_lvalue_reference<Second2> >::type* /* dummy */ = 0
, typename boost::enable_if<is_convertible<Second2, Second> >::type* /*dummy*/ = 0
) : second(std::forward<Second>(val)) {}
) : second(BOOST_FUSION_FWD_ELEM(Second, val)) {}
#endif
@@ -84,7 +84,7 @@ namespace boost { namespace fusion
BOOST_FUSION_GPU_ENABLED
pair& operator=(pair&& rhs)
{
second = std::forward<Second>(rhs.second);
second = BOOST_FUSION_FWD_ELEM(Second, rhs.second);
return *this;
}
#endif