Implement LWG 2488 - Make the placeholders constexpr. This patch makes the bind placeholders in std::placeholders both (1) const and (2) constexpr (See below). This is technically a breaking change for any code using the placeholders outside of std::bind and depending on them being non-const. However I don't think this will break any real world code. (1) Previously the placeholders were non-const extern globals in all dialects. This patch changes these extern globals to be const in all dialects. Since the cv-qualifiers don't participate in name mangling for globals this is an ABI compatible change. (2) Make the placeholders constexpr in C++11 and beyond. Although LWG 2488 only applies to C++17 I don't see any reason not to backport this change. git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@273824 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/functional b/include/functional index 9e4d5db..a13772f 100644 --- a/include/functional +++ b/include/functional
@@ -1980,16 +1980,29 @@ template <int _Np> struct __ph {}; -_LIBCPP_FUNC_VIS extern __ph<1> _1; -_LIBCPP_FUNC_VIS extern __ph<2> _2; -_LIBCPP_FUNC_VIS extern __ph<3> _3; -_LIBCPP_FUNC_VIS extern __ph<4> _4; -_LIBCPP_FUNC_VIS extern __ph<5> _5; -_LIBCPP_FUNC_VIS extern __ph<6> _6; -_LIBCPP_FUNC_VIS extern __ph<7> _7; -_LIBCPP_FUNC_VIS extern __ph<8> _8; -_LIBCPP_FUNC_VIS extern __ph<9> _9; -_LIBCPP_FUNC_VIS extern __ph<10> _10; +#if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_BIND) +_LIBCPP_FUNC_VIS extern const __ph<1> _1; +_LIBCPP_FUNC_VIS extern const __ph<2> _2; +_LIBCPP_FUNC_VIS extern const __ph<3> _3; +_LIBCPP_FUNC_VIS extern const __ph<4> _4; +_LIBCPP_FUNC_VIS extern const __ph<5> _5; +_LIBCPP_FUNC_VIS extern const __ph<6> _6; +_LIBCPP_FUNC_VIS extern const __ph<7> _7; +_LIBCPP_FUNC_VIS extern const __ph<8> _8; +_LIBCPP_FUNC_VIS extern const __ph<9> _9; +_LIBCPP_FUNC_VIS extern const __ph<10> _10; +#else +constexpr __ph<1> _1{}; +constexpr __ph<2> _2{}; +constexpr __ph<3> _3{}; +constexpr __ph<4> _4{}; +constexpr __ph<5> _5{}; +constexpr __ph<6> _6{}; +constexpr __ph<7> _7{}; +constexpr __ph<8> _8{}; +constexpr __ph<9> _9{}; +constexpr __ph<10> _10{}; +#endif // defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_BIND) } // placeholders 