Export of internal Abseil changes

--
91ca367a7548270155721bdda74611aeea2a2153 by Abseil Team <absl-team@google.com>:

Replace the only usage of btree_node::swap with simpler logic using transfers and delete btree_node::swap.

Add a benchmark for constructing small containers.

PiperOrigin-RevId: 301169874

--
ff9d73a7125b7f8ab5733cda877204dfbfac138e by Derek Mauro <dmauro@google.com>:

Ensure ABSL_CXX_STANDARD is set.
Fixes #640

PiperOrigin-RevId: 301160106

--
14ca0beee8c109e532134e7e9da7b072da1bf911 by Abseil Team <absl-team@google.com>:

Rollback the change to make Cord iterators a fixed size.  That change increased the iterator size, which can cause a deep recursion call to hit the stack memory limit, in turn causing a signal 11 failure.

PiperOrigin-RevId: 301084915

--
619e3cd9e56408bdb8b3b5a1e08dda1e95242264 by Matthew Brown <matthewbr@google.com>:

Internal Change

PiperOrigin-RevId: 300832828

--
64f8d62ab4c4c78077dbe85a9595a8eeb6d16608 by Gennadiy Rozental <rogeeff@google.com>:

Fix for empty braces support.

We will call proper aggregate construction in case when {} is used as default value. In other words instead of "new T", we'll call "new T{}".

PiperOrigin-RevId: 300715686

--
db3f65594d6db8b104b01262f884dff465b696ef by Abseil Team <absl-team@google.com>:

Emscripten supports thread-local storage nowadays.

PiperOrigin-RevId: 300675185
GitOrigin-RevId: 91ca367a7548270155721bdda74611aeea2a2153
Change-Id: I3344f745f9c3fc78775532b1808442fabd98e34a

absl/base/config.h

@@ -262,13 +262,6 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #endif
 #endif  // defined(__ANDROID__) && defined(__clang__)
 
-// Emscripten doesn't yet support `thread_local` or `__thread`.
-// https://github.com/emscripten-core/emscripten/issues/3502
-#if defined(__EMSCRIPTEN__)
-#undef ABSL_HAVE_TLS
-#undef ABSL_HAVE_THREAD_LOCAL
-#endif  // defined(__EMSCRIPTEN__)
-
 // ABSL_HAVE_INTRINSIC_INT128
 //
 // Checks whether the __int128 compiler extension for a 128-bit integral type is

absl/container/btree_benchmark.cc

@@ -134,6 +134,27 @@ void BM_InsertEnd(benchmark::State& state) {
   }
 }
 
+// Benchmark inserting the first few elements in a container. In b-tree, this is
+// when the root node grows.
+template <typename T>
+void BM_InsertSmall(benchmark::State& state) {
+  using V = typename remove_pair_const<typename T::value_type>::type;
+
+  const int kSize = 8;
+  std::vector<V> values = GenerateValues<V>(kSize);
+  T container;
+
+  while (state.KeepRunningBatch(kSize)) {
+    for (int i = 0; i < kSize; ++i) {
+      benchmark::DoNotOptimize(container.insert(values[i]));
+    }
+    state.PauseTiming();
+    // Do not measure the time it takes to clear the container.
+    container.clear();
+    state.ResumeTiming();
+  }
+}
+
 template <typename T>
 void BM_LookupImpl(benchmark::State& state, bool sorted) {
   using V = typename remove_pair_const<typename T::value_type>::type;
@@ -493,6 +514,7 @@ BTREE_TYPES(Time);
   MY_BENCHMARK4(type, Insert);            \
   MY_BENCHMARK4(type, InsertSorted);      \
   MY_BENCHMARK4(type, InsertEnd);         \
+  MY_BENCHMARK4(type, InsertSmall);       \
   MY_BENCHMARK4(type, Lookup);            \
   MY_BENCHMARK4(type, FullLookup);        \
   MY_BENCHMARK4(type, Delete);            \

absl/container/internal/btree.h

@@ -776,9 +776,6 @@ class btree_node {
   // delimiting key in the parent node onto itself.
   void merge(btree_node *src, allocator_type *alloc);
 
-  // Swaps the contents of `this` and `other`.
-  void swap(btree_node *other, allocator_type *alloc);
-
   // Node allocation/deletion routines.
   void init_leaf(btree_node *parent, int max_count) {
     set_parent(parent);
@@ -820,6 +817,14 @@ class btree_node {
     absl::container_internal::SanitizerPoisonObject(slot(i));
   }
 
+  // Transfers value from slot `src_i` in `src` to slot `dest_i` in `this`.
+  void transfer(const size_type dest_i, const size_type src_i, btree_node *src,
+                allocator_type *alloc) {
+    absl::container_internal::SanitizerUnpoisonObject(slot(dest_i));
+    params_type::transfer(alloc, slot(dest_i), src->slot(src_i));
+    absl::container_internal::SanitizerPoisonObject(src->slot(src_i));
+  }
+
   // Move n values starting at value i in this node into the values starting at
   // value j in dest_node.
   void uninitialized_move_n(const size_type n, const size_type i,
@@ -1752,54 +1757,6 @@ void btree_node<P>::merge(btree_node *src, allocator_type *alloc) {
   parent()->remove_value(position(), alloc);
 }
 
-template <typename P>
-void btree_node<P>::swap(btree_node *other, allocator_type *alloc) {
-  using std::swap;
-  assert(leaf() == other->leaf());
-
-  // Determine which is the smaller/larger node.
-  btree_node *smaller = this, *larger = other;
-  if (smaller->count() > larger->count()) {
-    swap(smaller, larger);
-  }
-
-  // Swap the values.
-  for (slot_type *a = smaller->start_slot(), *b = larger->start_slot(),
-                 *end = smaller->finish_slot();
-       a != end; ++a, ++b) {
-    params_type::swap(alloc, a, b);
-  }
-
-  // Move values that can't be swapped.
-  const size_type to_move = larger->count() - smaller->count();
-  larger->uninitialized_move_n(to_move, smaller->finish(), smaller->finish(),
-                               smaller, alloc);
-  larger->value_destroy_n(smaller->finish(), to_move, alloc);
-
-  if (!leaf()) {
-    // Swap the child pointers.
-    std::swap_ranges(&smaller->mutable_child(smaller->start()),
-                     &smaller->mutable_child(smaller->finish() + 1),
-                     &larger->mutable_child(larger->start()));
-    // Update swapped children's parent pointers.
-    int i = smaller->start();
-    int j = larger->start();
-    for (; i <= smaller->finish(); ++i, ++j) {
-      smaller->child(i)->set_parent(smaller);
-      larger->child(j)->set_parent(larger);
-    }
-    // Move the child pointers that couldn't be swapped.
-    for (; j <= larger->finish(); ++i, ++j) {
-      smaller->init_child(i, larger->child(j));
-      larger->clear_child(j);
-    }
-  }
-
-  // Swap the `finish`s.
-  // TODO(ezb): with floating storage, will also need to swap starts.
-  swap(mutable_finish(), other->mutable_finish());
-}
-
 ////
 // btree_iterator methods
 template <typename N, typename R, typename P>
@@ -2492,6 +2449,7 @@ inline auto btree<P>::internal_emplace(iterator iter, Args &&... args)
     ++iter.position;
   }
   const int max_count = iter.node->max_count();
+  allocator_type *alloc = mutable_allocator();
   if (iter.node->count() == max_count) {
     // Make room in the leaf for the new item.
     if (max_count < kNodeValues) {
@@ -2500,15 +2458,21 @@ inline auto btree<P>::internal_emplace(iterator iter, Args &&... args)
       assert(iter.node == root());
       iter.node =
           new_leaf_root_node((std::min<int>)(kNodeValues, 2 * max_count));
-      iter.node->swap(root(), mutable_allocator());
-      delete_leaf_node(root());
-      mutable_root() = rightmost_ = iter.node;
+      // Transfer the values from the old root to the new root.
+      node_type *old_root = root();
+      node_type *new_root = iter.node;
+      for (int i = old_root->start(), f = old_root->finish(); i < f; ++i) {
+        new_root->transfer(i, i, old_root, alloc);
+      }
+      new_root->set_finish(old_root->finish());
+      old_root->set_finish(old_root->start());
+      delete_leaf_node(old_root);
+      mutable_root() = rightmost_ = new_root;
     } else {
       rebalance_or_split(&iter);
     }
   }
-  iter.node->emplace_value(iter.position, mutable_allocator(),
-                           std::forward<Args>(args)...);
+  iter.node->emplace_value(iter.position, alloc, std::forward<Args>(args)...);
   ++size_;
   return iter;
 }

absl/copts/AbseilConfigureCopts.cmake

@@ -63,3 +63,5 @@ else()
   set(ABSL_DEFAULT_COPTS "")
   set(ABSL_TEST_COPTS "")
 endif()
+
+set(ABSL_CXX_STANDARD "${CMAKE_CXX_STANDARD}")

absl/flags/flag_test.cc

@@ -293,6 +293,18 @@ TEST_F(FlagTest, TestFlagDefinition) {
 // --------------------------------------------------------------------
 
 TEST_F(FlagTest, TestDefault) {
+  EXPECT_EQ(FLAGS_test_flag_01.DefaultValue(), "true");
+  EXPECT_EQ(FLAGS_test_flag_02.DefaultValue(), "1234");
+  EXPECT_EQ(FLAGS_test_flag_03.DefaultValue(), "-34");
+  EXPECT_EQ(FLAGS_test_flag_04.DefaultValue(), "189");
+  EXPECT_EQ(FLAGS_test_flag_05.DefaultValue(), "10765");
+  EXPECT_EQ(FLAGS_test_flag_06.DefaultValue(), "40000");
+  EXPECT_EQ(FLAGS_test_flag_07.DefaultValue(), "-1234567");
+  EXPECT_EQ(FLAGS_test_flag_08.DefaultValue(), "9876543");
+  EXPECT_EQ(FLAGS_test_flag_09.DefaultValue(), "-9.876e-50");
+  EXPECT_EQ(FLAGS_test_flag_10.DefaultValue(), "1.234e+12");
+  EXPECT_EQ(FLAGS_test_flag_11.DefaultValue(), "");
+
   EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_01), true);
   EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_02), 1234);
   EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_03), -34);
@@ -308,6 +320,61 @@ TEST_F(FlagTest, TestDefault) {
 
 // --------------------------------------------------------------------
 
+struct NonTriviallyCopyableAggregate {
+  NonTriviallyCopyableAggregate() = default;
+  NonTriviallyCopyableAggregate(const NonTriviallyCopyableAggregate& rhs)
+      : value(rhs.value) {}
+  NonTriviallyCopyableAggregate& operator=(
+      const NonTriviallyCopyableAggregate& rhs) {
+    value = rhs.value;
+    return *this;
+  }
+
+  int value;
+};
+bool AbslParseFlag(absl::string_view src, NonTriviallyCopyableAggregate* f,
+                   std::string* e) {
+  return absl::ParseFlag(src, &f->value, e);
+}
+std::string AbslUnparseFlag(const NonTriviallyCopyableAggregate& ntc) {
+  return absl::StrCat(ntc.value);
+}
+
+bool operator==(const NonTriviallyCopyableAggregate& ntc1,
+                const NonTriviallyCopyableAggregate& ntc2) {
+  return ntc1.value == ntc2.value;
+}
+
+}  // namespace
+
+ABSL_FLAG(bool, test_flag_eb_01, {}, "");
+ABSL_FLAG(int32_t, test_flag_eb_02, {}, "");
+ABSL_FLAG(int64_t, test_flag_eb_03, {}, "");
+ABSL_FLAG(double, test_flag_eb_04, {}, "");
+ABSL_FLAG(std::string, test_flag_eb_05, {}, "");
+ABSL_FLAG(NonTriviallyCopyableAggregate, test_flag_eb_06, {}, "");
+
+namespace {
+
+TEST_F(FlagTest, TestEmptyBracesDefault) {
+  EXPECT_EQ(FLAGS_test_flag_eb_01.DefaultValue(), "false");
+  EXPECT_EQ(FLAGS_test_flag_eb_02.DefaultValue(), "0");
+  EXPECT_EQ(FLAGS_test_flag_eb_03.DefaultValue(), "0");
+  EXPECT_EQ(FLAGS_test_flag_eb_04.DefaultValue(), "0");
+  EXPECT_EQ(FLAGS_test_flag_eb_05.DefaultValue(), "");
+  EXPECT_EQ(FLAGS_test_flag_eb_06.DefaultValue(), "0");
+
+  EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_eb_01), false);
+  EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_eb_02), 0);
+  EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_eb_03), 0);
+  EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_eb_04), 0.0);
+  EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_eb_05), "");
+  EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_eb_06),
+            NonTriviallyCopyableAggregate{});
+}
+
+// --------------------------------------------------------------------
+
 TEST_F(FlagTest, TestGetSet) {
   absl::SetFlag(&FLAGS_test_flag_01, false);
   EXPECT_EQ(absl::GetFlag(FLAGS_test_flag_01), false);

absl/flags/internal/flag.h

@@ -647,7 +647,7 @@ T* MakeFromDefaultValue(T t) {
 
 template <typename T>
 T* MakeFromDefaultValue(EmptyBraces) {
-  return new T;
+  return new T{};
 }
 
 }  // namespace flags_internal

absl/strings/cord.h

@@ -48,6 +48,7 @@
 #include "absl/base/internal/per_thread_tls.h"
 #include "absl/base/macros.h"
 #include "absl/base/port.h"
+#include "absl/container/inlined_vector.h"
 #include "absl/functional/function_ref.h"
 #include "absl/meta/type_traits.h"
 #include "absl/strings/internal/cord_internal.h"
@@ -67,55 +68,6 @@ template <typename H>
 H HashFragmentedCord(H, const Cord&);
 }
 
-namespace cord_internal {
-
-// It's expensive to keep a tree perfectly balanced, so instead we keep trees
-// approximately balanced.  A tree node N of depth D(N) that contains a string
-// of L(N) characters is considered balanced if L >= Fibonacci(D + 2).
-// The "+ 2" is used to ensure that every balanced leaf node contains at least
-//  one character. Here we presume that
-//   Fibonacci(0) = 0
-//   Fibonacci(1) = 1
-//   Fibonacci(2) = 1
-//   Fibonacci(3) = 2
-//   ...
-// The algorithm is based on paper by Hans Boehm et al:
-// https://www.cs.rit.edu/usr/local/pub/jeh/courses/QUARTERS/FP/Labs/CedarRope/rope-paper.pdf
-// In this paper authors shows that rebalancing based on cord forest of already
-// balanced subtrees can be proven to never produce tree of depth larger than
-// largest Fibonacci number representable in the same integral type as cord size
-// For 64 bit integers this is the 93rd Fibonacci number. For 32 bit integrals
-// this is 47th Fibonacci number.
-constexpr size_t MaxCordDepth() { return sizeof(size_t) == 8 ? 93 : 47; }
-
-// This class models fixed max size stack of CordRep pointers.
-// The elements are being pushed back and popped from the back.
-template <typename CordRepPtr, size_t N>
-class CordTreePath {
- public:
-  CordTreePath() {}
-  explicit CordTreePath(CordRepPtr root) { push_back(root); }
-
-  bool empty() const { return size_ == 0; }
-  size_t size() const { return size_; }
-  void clear() { size_ = 0; }
-
-  CordRepPtr back() { return data_[size_ - 1]; }
-
-  void pop_back() {
-    --size_;
-    assert(size_ < N);
-  }
-  void push_back(CordRepPtr elem) { data_[size_++] = elem; }
-
- private:
-  CordRepPtr data_[N];
-  size_t size_ = 0;
-};
-
-using CordTreeMutablePath = CordTreePath<CordRep*, MaxCordDepth()>;
-}  // namespace cord_internal
-
 // A Cord is a sequence of characters.
 class Cord {
  private:
@@ -333,7 +285,8 @@ class Cord {
     absl::cord_internal::CordRep* current_leaf_ = nullptr;
     // The number of bytes left in the `Cord` over which we are iterating.
     size_t bytes_remaining_ = 0;
-    absl::cord_internal::CordTreeMutablePath stack_of_right_children_;
+    absl::InlinedVector<absl::cord_internal::CordRep*, 4>
+        stack_of_right_children_;
   };
 
   // Returns an iterator to the first chunk of the `Cord`.

absl/strings/cord_test.cc

@@ -1402,53 +1402,6 @@ TEST(CordChunkIterator, Operations) {
   VerifyChunkIterator(subcords, 128);
 }
 
-TEST(CordChunkIterator, MaxLengthFullTree) {
-  // Start with a 1-byte cord, and then double its length in a loop.  We should
-  // be able to do this until the point where we would overflow size_t.
-
-  absl::Cord cord;
-  size_t size = 1;
-  AddExternalMemory("x", &cord);
-  EXPECT_EQ(cord.size(), size);
-
-  const int kCordLengthDoublingLimit = std::numeric_limits<size_t>::digits - 1;
-  for (int i = 0; i < kCordLengthDoublingLimit; ++i) {
-    cord.Prepend(absl::Cord(cord));
-    size <<= 1;
-
-    EXPECT_EQ(cord.size(), size);
-
-    auto chunk_it = cord.chunk_begin();
-    EXPECT_EQ(*chunk_it, "x");
-  }
-
-  EXPECT_DEATH_IF_SUPPORTED(
-      (cord.Prepend(absl::Cord(cord)), *cord.chunk_begin()),
-      "Cord is too long");
-}
-
-TEST(CordChunkIterator, MaxDepth) {
-  // By reusing nodes, it's possible in pathological cases to build a Cord that
-  // exceeds both the maximum permissible length and depth.  In this case, the
-  // violation of the maximum depth is reported.
-  absl::Cord left_child;
-  AddExternalMemory("x", &left_child);
-  absl::Cord root = left_child;
-
-  for (int i = 0; i < absl::cord_internal::MaxCordDepth() - 2; ++i) {
-    size_t new_size = left_child.size() + root.size();
-    root.Prepend(left_child);
-    EXPECT_EQ(root.size(), new_size);
-
-    auto chunk_it = root.chunk_begin();
-    EXPECT_EQ(*chunk_it, "x");
-
-    std::swap(left_child, root);
-  }
-
-  EXPECT_DEATH_IF_SUPPORTED(root.Prepend(left_child), "Cord is too long");
-}
-
 TEST(CordCharIterator, Traits) {
   static_assert(std::is_copy_constructible<absl::Cord::CharIterator>::value,
                 "");

absl/strings/internal/str_format/extension.h

@@ -24,6 +24,7 @@
 
 #include "absl/base/config.h"
 #include "absl/base/port.h"
+#include "absl/meta/type_traits.h"
 #include "absl/strings/internal/str_format/output.h"
 #include "absl/strings/string_view.h"
 
@@ -365,11 +366,22 @@ constexpr FormatConversionCharSet operator|(FormatConversionCharSet a,
                                  static_cast<uint64_t>(b));
 }
 
+// Overloaded conversion functions to support absl::ParsedFormat.
 // Get a conversion with a single character in it.
-constexpr FormatConversionCharSet ConversionCharToConv(char c) {
-  return FormatConversionCharSet(FormatConversionCharToConvValue(c));
+constexpr FormatConversionCharSet ToFormatConversionCharSet(char c) {
+  return static_cast<FormatConversionCharSet>(
+      FormatConversionCharToConvValue(c));
 }
 
+// Get a conversion with a single character in it.
+constexpr FormatConversionCharSet ToFormatConversionCharSet(
+    FormatConversionCharSet c) {
+  return c;
+}
+
+template <typename T>
+void ToFormatConversionCharSet(T) = delete;
+
 // Checks whether `c` exists in `set`.
 constexpr bool Contains(FormatConversionCharSet set, char c) {
   return (static_cast<uint64_t>(set) & FormatConversionCharToConvValue(c)) != 0;

absl/strings/str_format.h

@@ -285,7 +285,7 @@ using FormatSpec =
 //   }
 template <char... Conv>
 using ParsedFormat = str_format_internal::ExtendedParsedFormat<
-    str_format_internal::ConversionCharToConv(Conv)...>;
+    absl::str_format_internal::ToFormatConversionCharSet(Conv)...>;
 
 // StrFormat()
 //

ci/macos_xcode_cmake.sh

@@ -36,7 +36,7 @@ for compilation_mode in ${ABSL_CMAKE_BUILD_TYPES}; do
   time cmake ${ABSEIL_ROOT} \
     -GXcode \
     -DCMAKE_BUILD_TYPE=${compilation_mode} \
-    -DCMAKE_CXX_FLAGS=-std=c++14 \
+    -DCMAKE_CXX_STANDARD=11 \
     -DABSL_USE_GOOGLETEST_HEAD=ON \
     -DABSL_RUN_TESTS=ON
   time cmake --build .