summaryrefslogtreecommitdiff
path: root/absl/container/internal/container_memory.h
diff options
context:
space:
mode:
Diffstat (limited to 'absl/container/internal/container_memory.h')
-rw-r--r--absl/container/internal/container_memory.h15
1 files changed, 15 insertions, 0 deletions
diff --git a/absl/container/internal/container_memory.h b/absl/container/internal/container_memory.h
index c7777a93..d02c576d 100644
--- a/absl/container/internal/container_memory.h
+++ b/absl/container/internal/container_memory.h
@@ -18,6 +18,7 @@
#include <cassert>
#include <cstddef>
#include <memory>
+#include <new>
#include <tuple>
#include <type_traits>
#include <utility>
@@ -352,6 +353,20 @@ struct map_slot_policy {
return slot->value;
}
+ // When C++17 is available, we can use std::launder to provide mutable
+ // access to the key for use in node handle.
+#if defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606
+ static K& mutable_key(slot_type* slot) {
+ // Still check for kMutableKeys so that we can avoid calling std::launder
+ // unless necessary because it can interfere with optimizations.
+ return kMutableKeys::value ? slot->key
+ : *std::launder(const_cast<K*>(
+ std::addressof(slot->value.first)));
+ }
+#else // !(defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606)
+ static const K& mutable_key(slot_type* slot) { return key(slot); }
+#endif
+
static const K& key(const slot_type* slot) {
return kMutableKeys::value ? slot->key : slot->value.first;
}