[libcxx-commits] [PATCH] D105597: [libcxx][nfc] Remove <variant>'s dependence on <array>.

[Zoe Carver via Phabricator via libcxx-commits]

zoecarver created this revision.
zoecarver added reviewers: cjdb, Quuxplusone, ldionne.
zoecarver requested review of this revision.
Herald added a project: libc++.
Herald added a subscriber: libcxx-commits.
Herald added a reviewer: libc++.

This will allow us to use variant in common_iterator. We do this by introducing a new `__light_array` type that variant uses instead of `std::array`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D105597

Files:
  libcxx/include/variant


Index: libcxx/include/variant
===================================================================
--- libcxx/include/variant
+++ libcxx/include/variant
@@ -203,7 +203,6 @@
 #include <__config>
 #include <__utility/forward.h>
 #include <__tuple>
-#include <array>
 #include <compare>
 #include <exception>
 #include <functional>
@@ -238,6 +237,30 @@
 //       Remove this once we drop support for GCC 5.
 #if _LIBCPP_STD_VER > 14 && !(defined(_LIBCPP_COMPILER_GCC) && _GNUC_VER_NEW < 6000)
 
+template<class _Tp, size_t _Size>
+struct __light_array {
+  _Tp __buff_[_Size] = {0};
+
+  inline _LIBCPP_INLINE_VISIBILITY constexpr
+  _Tp &operator[](size_t __n) noexcept {
+      return __buff_[__n];
+  }
+
+  inline _LIBCPP_INLINE_VISIBILITY constexpr
+  const _Tp &operator[](size_t __n) const noexcept {
+      return __buff_[__n];
+  }
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  constexpr friend bool
+  operator==(const __light_array& __x, const __light_array& __y) noexcept {
+      for (size_t __i = 0; __i < _Size; ++__i)
+        if (__x.__buff_[__i] != __y.__buff_[__i])
+          return false;
+      return true;
+  }
+};
+
 _LIBCPP_NORETURN
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
@@ -498,7 +521,7 @@
 
   template <class _Tp, size_t _Np, typename... _Indices>
   inline _LIBCPP_INLINE_VISIBILITY
-  static constexpr auto&& __at(const array<_Tp, _Np>& __elems,
+  static constexpr auto&& __at(const __light_array<_Tp, _Np>& __elems,
                                size_t __index, _Indices... __indices) {
     return __at(__elems[__index], __indices...);
   }
@@ -514,8 +537,8 @@
   inline _LIBCPP_INLINE_VISIBILITY
   static constexpr auto __make_farray(_Fs&&... __fs) {
     __std_visit_visitor_return_type_check<__uncvref_t<_Fs>...>();
-    using __result = array<common_type_t<__uncvref_t<_Fs>...>, sizeof...(_Fs)>;
-    return __result{{_VSTD::forward<_Fs>(__fs)...}};
+    using __result = __light_array<common_type_t<__uncvref_t<_Fs>...>, sizeof...(_Fs)>;
+    return __result{_VSTD::forward<_Fs>(__fs)...};
   }
 
   template <size_t... _Is>


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