Fix LWG issue 2469 - Use piecewise construction in unordered_map::operator[].

unordered_map's allocator may only be used to construct objects of 'value_type',
or in this case 'pair<const Key, Value>'. In order to respect this requirement
in operator[], which requires default constructing the 'mapped_type', we have
to use pair's piecewise constructor with '(tuple<Kep>, tuple<>)'.

Unfortunately we still need to provide a fallback implementation for C++03
since we don't have <tuple>. Even worse this fallback is the last remaining
user of '__hash_map_node_destructor' and '__construct_node_with_key'.

llvm-svn: 260601

2 files changed, 52 insertions, 12 deletions

diff --git a/libcxx/test/std/containers/unord/unord.map/unord.map.elem/index.pass.cpp b/libcxx/test/std/containers/unord/unord.map/unord.map.elem/index.pass.cpp
index c072248f866..4757c926f68 100644
--- a/libcxx/test/std/containers/unord/unord.map/unord.map.elem/index.pass.cpp
+++ b/libcxx/test/std/containers/unord/unord.map/unord.map.elem/index.pass.cpp
@@ -19,8 +19,11 @@
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
 #include "MoveOnly.h"
 #include "min_allocator.h"
+#include "count_new.hpp"
+#include "container_test_types.h"
 
 int main()
 {
@@ -44,7 +47,7 @@ int main()
         assert(c.size() == 5);
         assert(c.at(11) == "eleven");
     }
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#if TEST_STD_VER >= 11
     {
         typedef std::unordered_map<MoveOnly, std::string> C;
         typedef std::pair<int, std::string> P;
@@ -65,8 +68,6 @@ int main()
         assert(c.size() == 5);
         assert(c.at(11) == "eleven");
     }
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#if __cplusplus >= 201103L
     {
         typedef std::unordered_map<int, std::string, std::hash<int>, std::equal_to<int>,
                             min_allocator<std::pair<const int, std::string>>> C;
@@ -88,7 +89,7 @@ int main()
         assert(c.size() == 5);
         assert(c.at(11) == "eleven");
     }
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
     {
         typedef std::unordered_map<MoveOnly, std::string, std::hash<MoveOnly>, std::equal_to<MoveOnly>,
                             min_allocator<std::pair<const MoveOnly, std::string>>> C;
@@ -110,6 +111,50 @@ int main()
         assert(c.size() == 5);
         assert(c.at(11) == "eleven");
     }
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+    {
+        using Container = TCT::unordered_map<>;
+        using Key = Container::key_type;
+        using MappedType = Container::mapped_type;
+        using ValueTp = Container::value_type;
+        ConstructController* cc = getConstructController();
+        cc->reset();
+        {
+            Container c;
+            const Key k(1);
+            cc->expect<std::piecewise_construct_t const&, std::tuple<Key const&>&&, std::tuple<>&&>();
+            MappedType& mref = c[k];
+            assert(!cc->unchecked());
+            {
+                DisableAllocationGuard g;
+                MappedType& mref2 = c[k];
+                assert(&mref == &mref2);
+            }
+        }
+        {
+            Container c;
+            Key k(1);
+            cc->expect<std::piecewise_construct_t const&, std::tuple<Key const&>&&, std::tuple<>&&>();
+            MappedType& mref = c[k];
+            assert(!cc->unchecked());
+            {
+                DisableAllocationGuard g;
+                MappedType& mref2 = c[k];
+                assert(&mref == &mref2);
+            }
+        }
+        {
+            Container c;
+            Key k(1);
+            cc->expect<std::piecewise_construct_t const&, std::tuple<Key &&>&&, std::tuple<>&&>();
+            MappedType& mref = c[std::move(k)];
+            assert(!cc->unchecked());
+            {
+                Key k2(1);
+                DisableAllocationGuard g;
+                MappedType& mref2 = c[std::move(k2)];
+                assert(&mref == &mref2);
+            }
+        }
+    }
 #endif
 }
diff --git a/libcxx/test/std/containers/unord/unord.map/unord.map.elem/index_tuple.pass.cpp b/libcxx/test/std/containers/unord/unord.map/unord.map.elem/index_tuple.pass.cpp
index c319b5c30b2..f2c694e86f7 100644
--- a/libcxx/test/std/containers/unord/unord.map/unord.map.elem/index_tuple.pass.cpp
+++ b/libcxx/test/std/containers/unord/unord.map/unord.map.elem/index_tuple.pass.cpp
@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// UNSUPPORTED: c++98, c++03
+
 // <unordered_map>
 
 // template <class Key, class T, class Hash = hash<Key>, class Pred = equal_to<Key>,
@@ -18,9 +20,6 @@
 // http://llvm.org/bugs/show_bug.cgi?id=16542
 
 #include <unordered_map>
-
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
 #include <tuple>
 
 using namespace std;
@@ -30,12 +29,8 @@ struct my_hash
     size_t operator()(const tuple<int,int>&) const {return 0;}
 };
 
-#endif
-
 int main()
 {
-#ifndef _LIBCPP_HAS_NO_VARIADICS
     unordered_map<tuple<int,int>, size_t, my_hash> m;
     m[make_tuple(2,3)]=7;
-#endif
 }