Changes imported from Abseil "staging" branch:

  - a42e9b454ca8be7d021789cdb9bcada07d3e2d3e Merge pull request #57. by Derek Mauro <dmauro@google.com>
  - b1e03838f059c034a6489501804d516326246042 Move the long ostream tests into a separate source file u... by Alex Strelnikov <strel@google.com>
  - 7c56b7dbb05faa7e8653632e00be470331d79cb9 Return reference from absl::InlinedVector::emplace_back(). by Abseil Team <absl-team@google.com>
  - 85b070822b62688ff348d9ad9cc9e230a851f617 Treat \u or \U followed by Unicode surrogate character as... by Abseil Team <absl-team@google.com>

GitOrigin-RevId: a42e9b454ca8be7d021789cdb9bcada07d3e2d3e
Change-Id: I7d8fb68ffd7eb4e9e737f21fbed6d56b71985f94

2 files changed, 25 insertions, 7 deletions

diff --git a/absl/container/inlined_vector.h b/absl/container/inlined_vector.h
index e0bb900c..4bf9c18a 100644
--- a/absl/container/inlined_vector.h
+++ b/absl/container/inlined_vector.h
@@ -365,13 +365,14 @@ class InlinedVector {
   // InlinedVector::emplace_back()
   //
   // Constructs and appends an object to the inlined vector.
+  //
+  // Returns a reference to the inserted element.
   template <typename... Args>
-  void emplace_back(Args&&... args) {
+  value_type& emplace_back(Args&&... args) {
     size_type s = size();
     assert(s <= capacity());
     if (ABSL_PREDICT_FALSE(s == capacity())) {
-      GrowAndEmplaceBack(std::forward<Args>(args)...);
-      return;
+      return GrowAndEmplaceBack(std::forward<Args>(args)...);
     }
     assert(s < capacity());
 
@@ -383,7 +384,7 @@ class InlinedVector {
       tag().set_inline_size(s + 1);
       space = inlined_space();
     }
-    Construct(space + s, std::forward<Args>(args)...);
+    return Construct(space + s, std::forward<Args>(args)...);
   }
 
   // InlinedVector::push_back()
@@ -703,26 +704,30 @@ class InlinedVector {
   }
 
   template <typename... Args>
-  void GrowAndEmplaceBack(Args&&... args) {
+  value_type& GrowAndEmplaceBack(Args&&... args) {
     assert(size() == capacity());
     const size_type s = size();
 
     Allocation new_allocation(allocator(), 2 * capacity());
 
-    Construct(new_allocation.buffer() + s, std::forward<Args>(args)...);
+    value_type& new_element =
+        Construct(new_allocation.buffer() + s, std::forward<Args>(args)...);
     UninitializedCopy(std::make_move_iterator(data()),
                       std::make_move_iterator(data() + s),
                       new_allocation.buffer());
 
     ResetAllocation(new_allocation, s + 1);
+
+    return new_element;
   }
 
   void InitAssign(size_type n);
   void InitAssign(size_type n, const value_type& t);
 
   template <typename... Args>
-  void Construct(pointer p, Args&&... args) {
+  value_type& Construct(pointer p, Args&&... args) {
     AllocatorTraits::construct(allocator(), p, std::forward<Args>(args)...);
+    return *p;
   }
 
   template <typename Iter>
diff --git a/absl/container/inlined_vector_test.cc b/absl/container/inlined_vector_test.cc
index 055bca98..8527ba1a 100644
--- a/absl/container/inlined_vector_test.cc
+++ b/absl/container/inlined_vector_test.cc
@@ -393,6 +393,19 @@ TEST(InlinedVectorTest, Noexcept) {
                 absl::InlinedVector<MoveCanThrow, 2>>::value));
 }
 
+TEST(InlinedVectorTest, EmplaceBack) {
+  absl::InlinedVector<std::pair<std::string, int>, 1> v;
+
+  auto& inlined_element = v.emplace_back("answer", 42);
+  EXPECT_EQ(&inlined_element, &v[0]);
+  EXPECT_EQ(inlined_element.first, "answer");
+  EXPECT_EQ(inlined_element.second, 42);
+
+  auto& allocated_element = v.emplace_back("taxicab", 1729);
+  EXPECT_EQ(&allocated_element, &v[1]);
+  EXPECT_EQ(allocated_element.first, "taxicab");
+  EXPECT_EQ(allocated_element.second, 1729);
+}
 
 TEST(IntVec, Insert) {
   for (int len = 0; len < 20; len++) {