ConcurrentHashMap set size and max_size.

Summary:
During move construction and assignment `size_` and `max_size_` aren't set.
Added a test case that attempted to allocate 4096 GB before the patch, and passes after.

Reviewed By: yfeldblum

Differential Revision: D7005041

fbshipit-source-id: b42a0a408ce49ddded4ba805fc064cd11df2457e

folly/concurrency/ConcurrentHashMap.h

@@ -126,7 +126,8 @@ class ConcurrentHashMap {
     }
   }
 
-  ConcurrentHashMap(ConcurrentHashMap&& o) noexcept {
+  ConcurrentHashMap(ConcurrentHashMap&& o) noexcept
+      : size_(o.size_), max_size_(o.max_size_) {
     for (uint64_t i = 0; i < NumShards; i++) {
       segments_[i].store(
           o.segments_[i].load(std::memory_order_relaxed),
@@ -147,6 +148,8 @@ class ConcurrentHashMap {
           std::memory_order_relaxed);
       o.segments_[i].store(nullptr, std::memory_order_relaxed);
     }
+    size_ = o.size_;
+    max_size_ = o.max_size_;
     return *this;
   }
 

folly/concurrency/test/ConcurrentHashMapTest.cpp

@@ -249,6 +249,19 @@ TEST(ConcurrentHashMap, MapIterateTest) {
   EXPECT_EQ(count, 2);
 }
 
+TEST(ConcurrentHashMap, MoveIterateAssignIterate) {
+  using Map = ConcurrentHashMap<int, int>;
+  Map tmp;
+  Map map{std::move(tmp)};
+
+  map.insert(0, 0);
+  ++map.cbegin();
+  ConcurrentHashMap<int, int> other;
+  other.insert(0, 0);
+  map = std::move(other);
+  ++map.cbegin();
+}
+
 TEST(ConcurrentHashMap, EraseTest) {
   ConcurrentHashMap<uint64_t, uint64_t> foomap(3);
   foomap.insert(1, 0);