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.
llvm-svn: 273824
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 555330719a31dd4294741493781bebe41cd6afbb
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