Export of internal Abseil changes

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730bb88bee556aa11fa19aa33e1434cb6fa78985 by Evan Brown <ezb@google.com>:

Support missing allocator-related constructors in b-tree. See [reference](https://en.cppreference.com/w/cpp/container/set/set).

Also use allocator_traits::select_on_container_copy_construction() to get allocator for copy construction.

PiperOrigin-RevId: 339058322

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b6cc121689ae3e452d1db2d66122cb198d25142b by Derek Mauro <dmauro@google.com>:

Fix more sign-compare warnings

PiperOrigin-RevId: 339057920

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0e2c62da1dcaf6529abab952bdcc96c6de2d9506 by Abseil Team <absl-team@google.com>:

Add missing <limits> include

PiperOrigin-RevId: 339054753

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d5a9ec2d1e40fe6359e720942e4955009ee415ec by Derek Mauro <dmauro@google.com>:

Stop disabling sign-compare warnings for non-test targets.
Our users complain about these.

This does not catch issues in header-only libraries (like btree.h)
but we may work on those in the future

PiperOrigin-RevId: 338967089

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0c062c542a4c61ea0f65d25811827c0858e3adde by Abseil Team <absl-team@google.com>:

Improve cache-locality for ThreadIdentity and PerThreadSynch.

This is a change based on an observation in RPC benchmarks that shows
significant cycles being spent in waking up a thread, 99.8% of which
was on cache misses. Investigating this a bit more, it turns out to
be due to sharing the cache line with the waiter state.

To fix this issue, the following changes are introduced:
- Reorder fields in PerThreadSync so that it fits in a single cache line
  The size of this structure was 80 bytes before this change.
  Note: Manually inspected all booleans to make sure they are not modified by
        multiple threads concurrently.

PiperOrigin-RevId: 338852058

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a90d6f2b2346385017e32dd8ae1b5ca691a5863f by Derek Mauro <dmauro@google.com>:

Delete GCC 4.9 test script. It is no longer supported

PiperOrigin-RevId: 338779452

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7274008d4757e88869110be9db39d03d911ae2b5 by Abseil Team <absl-team@google.com>:

Fix the usage example in which SetFlag should take a pointer.

PiperOrigin-RevId: 338744529
GitOrigin-RevId: 730bb88bee556aa11fa19aa33e1434cb6fa78985
Change-Id: Iff99594c4022e60e482a392d334b376c7ae8883e

absl/base/internal/thread_identity.h

@@ -32,6 +32,7 @@
 
 #include "absl/base/config.h"
 #include "absl/base/internal/per_thread_tls.h"
+#include "absl/base/optimization.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
@@ -69,30 +70,28 @@ struct PerThreadSynch {
                          // is using this PerThreadSynch as a terminator.  Its
                          // skip field must not be filled in because the loop
                          // might then skip over the terminator.
-
-  // The wait parameters of the current wait.  waitp is null if the
-  // thread is not waiting. Transitions from null to non-null must
-  // occur before the enqueue commit point (state = kQueued in
-  // Enqueue() and CondVarEnqueue()). Transitions from non-null to
-  // null must occur after the wait is finished (state = kAvailable in
-  // Mutex::Block() and CondVar::WaitCommon()). This field may be
-  // changed only by the thread that describes this PerThreadSynch.  A
-  // special case is Fer(), which calls Enqueue() on another thread,
-  // but with an identical SynchWaitParams pointer, thus leaving the
-  // pointer unchanged.
-  SynchWaitParams *waitp;
-
-  bool suppress_fatal_errors;  // If true, try to proceed even in the face of
-                               // broken invariants.  This is used within fatal
-                               // signal handlers to improve the chances of
-                               // debug logging information being output
-                               // successfully.
-
-  intptr_t readers;     // Number of readers in mutex.
-  int priority;         // Priority of thread (updated every so often).
-
-  // When priority will next be read (cycles).
-  int64_t next_priority_read_cycles;
+  bool wake;             // This thread is to be woken from a Mutex.
+  // If "x" is on a waiter list for a mutex, "x->cond_waiter" is true iff the
+  // waiter is waiting on the mutex as part of a CV Wait or Mutex Await.
+  //
+  // The value of "x->cond_waiter" is meaningless if "x" is not on a
+  // Mutex waiter list.
+  bool cond_waiter;
+  bool maybe_unlocking;  // Valid at head of Mutex waiter queue;
+                         // true if UnlockSlow could be searching
+                         // for a waiter to wake.  Used for an optimization
+                         // in Enqueue().  true is always a valid value.
+                         // Can be reset to false when the unlocker or any
+                         // writer releases the lock, or a reader fully
+                         // releases the lock.  It may not be set to false
+                         // by a reader that decrements the count to
+                         // non-zero. protected by mutex spinlock
+  bool suppress_fatal_errors;  // If true, try to proceed even in the face
+                               // of broken invariants.  This is used within
+                               // fatal signal handlers to improve the
+                               // chances of debug logging information being
+                               // output successfully.
+  int priority;                // Priority of thread (updated every so often).
 
   // State values:
   //   kAvailable: This PerThreadSynch is available.
@@ -111,30 +110,30 @@ struct PerThreadSynch {
   };
   std::atomic<State> state;
 
-  bool maybe_unlocking;  // Valid at head of Mutex waiter queue;
-                         // true if UnlockSlow could be searching
-                         // for a waiter to wake.  Used for an optimization
-                         // in Enqueue().  true is always a valid value.
-                         // Can be reset to false when the unlocker or any
-                         // writer releases the lock, or a reader fully releases
-                         // the lock.  It may not be set to false by a reader
-                         // that decrements the count to non-zero.
-                         // protected by mutex spinlock
+  // The wait parameters of the current wait.  waitp is null if the
+  // thread is not waiting. Transitions from null to non-null must
+  // occur before the enqueue commit point (state = kQueued in
+  // Enqueue() and CondVarEnqueue()). Transitions from non-null to
+  // null must occur after the wait is finished (state = kAvailable in
+  // Mutex::Block() and CondVar::WaitCommon()). This field may be
+  // changed only by the thread that describes this PerThreadSynch.  A
+  // special case is Fer(), which calls Enqueue() on another thread,
+  // but with an identical SynchWaitParams pointer, thus leaving the
+  // pointer unchanged.
+  SynchWaitParams* waitp;
 
-  bool wake;  // This thread is to be woken from a Mutex.
+  intptr_t readers;     // Number of readers in mutex.
 
-  // If "x" is on a waiter list for a mutex, "x->cond_waiter" is true iff the
-  // waiter is waiting on the mutex as part of a CV Wait or Mutex Await.
-  //
-  // The value of "x->cond_waiter" is meaningless if "x" is not on a
-  // Mutex waiter list.
-  bool cond_waiter;
+  // When priority will next be read (cycles).
+  int64_t next_priority_read_cycles;
 
   // Locks held; used during deadlock detection.
   // Allocated in Synch_GetAllLocks() and freed in ReclaimThreadIdentity().
   SynchLocksHeld *all_locks;
 };
 
+// The instances of this class are allocated in NewThreadIdentity() with an
+// alignment of PerThreadSynch::kAlignment.
 struct ThreadIdentity {
   // Must be the first member.  The Mutex implementation requires that
   // the PerThreadSynch object associated with each thread is

absl/container/btree_test.cc

@@ -2709,6 +2709,101 @@ TEST(Btree, MultiKeyEqualRange) {
   }
 }
 
+TEST(Btree, AllocConstructor) {
+  using Alloc = CountingAllocator<int>;
+  using Set = absl::btree_set<int, std::less<int>, Alloc>;
+  int64_t bytes_used = 0;
+  Alloc alloc(&bytes_used);
+  Set set(alloc);
+
+  set.insert({1, 2, 3});
+
+  EXPECT_THAT(set, ElementsAre(1, 2, 3));
+  EXPECT_GT(bytes_used, set.size() * sizeof(int));
+}
+
+TEST(Btree, AllocInitializerListConstructor) {
+  using Alloc = CountingAllocator<int>;
+  using Set = absl::btree_set<int, std::less<int>, Alloc>;
+  int64_t bytes_used = 0;
+  Alloc alloc(&bytes_used);
+  Set set({1, 2, 3}, alloc);
+
+  EXPECT_THAT(set, ElementsAre(1, 2, 3));
+  EXPECT_GT(bytes_used, set.size() * sizeof(int));
+}
+
+TEST(Btree, AllocRangeConstructor) {
+  using Alloc = CountingAllocator<int>;
+  using Set = absl::btree_set<int, std::less<int>, Alloc>;
+  int64_t bytes_used = 0;
+  Alloc alloc(&bytes_used);
+  std::vector<int> v = {1, 2, 3};
+  Set set(v.begin(), v.end(), alloc);
+
+  EXPECT_THAT(set, ElementsAre(1, 2, 3));
+  EXPECT_GT(bytes_used, set.size() * sizeof(int));
+}
+
+TEST(Btree, AllocCopyConstructor) {
+  using Alloc = CountingAllocator<int>;
+  using Set = absl::btree_set<int, std::less<int>, Alloc>;
+  int64_t bytes_used1 = 0;
+  Alloc alloc1(&bytes_used1);
+  Set set1(alloc1);
+
+  set1.insert({1, 2, 3});
+
+  int64_t bytes_used2 = 0;
+  Alloc alloc2(&bytes_used2);
+  Set set2(set1, alloc2);
+
+  EXPECT_THAT(set1, ElementsAre(1, 2, 3));
+  EXPECT_THAT(set2, ElementsAre(1, 2, 3));
+  EXPECT_GT(bytes_used1, set1.size() * sizeof(int));
+  EXPECT_EQ(bytes_used1, bytes_used2);
+}
+
+TEST(Btree, AllocMoveConstructor_SameAlloc) {
+  using Alloc = CountingAllocator<int>;
+  using Set = absl::btree_set<int, std::less<int>, Alloc>;
+  int64_t bytes_used = 0;
+  Alloc alloc(&bytes_used);
+  Set set1(alloc);
+
+  set1.insert({1, 2, 3});
+
+  const int64_t original_bytes_used = bytes_used;
+  EXPECT_GT(original_bytes_used, set1.size() * sizeof(int));
+
+  Set set2(std::move(set1), alloc);
+
+  EXPECT_THAT(set2, ElementsAre(1, 2, 3));
+  EXPECT_EQ(bytes_used, original_bytes_used);
+}
+
+TEST(Btree, AllocMoveConstructor_DifferentAlloc) {
+  using Alloc = CountingAllocator<int>;
+  using Set = absl::btree_set<int, std::less<int>, Alloc>;
+  int64_t bytes_used1 = 0;
+  Alloc alloc1(&bytes_used1);
+  Set set1(alloc1);
+
+  set1.insert({1, 2, 3});
+
+  const int64_t original_bytes_used = bytes_used1;
+  EXPECT_GT(original_bytes_used, set1.size() * sizeof(int));
+
+  int64_t bytes_used2 = 0;
+  Alloc alloc2(&bytes_used2);
+  Set set2(std::move(set1), alloc2);
+
+  EXPECT_THAT(set2, ElementsAre(1, 2, 3));
+  // We didn't free these bytes allocated by `set1` yet.
+  EXPECT_EQ(bytes_used1, original_bytes_used);
+  EXPECT_EQ(bytes_used2, original_bytes_used);
+}
+
 }  // namespace
 }  // namespace container_internal
 ABSL_NAMESPACE_END

absl/container/internal/btree.h

@@ -1141,21 +1141,35 @@ class btree {
   // before this method is called. This method is used in copy construction,
   // copy assignment, and move assignment.
   template <typename Btree>
-  void copy_or_move_values_in_order(Btree *other);
+  void copy_or_move_values_in_order(Btree &other);
 
   // Validates that various assumptions/requirements are true at compile time.
   constexpr static bool static_assert_validation();
 
  public:
-  btree(const key_compare &comp, const allocator_type &alloc);
+  btree(const key_compare &comp, const allocator_type &alloc)
+      : root_(comp, alloc, EmptyNode()), rightmost_(EmptyNode()), size_(0) {}
 
-  btree(const btree &other);
+  btree(const btree &other) : btree(other, other.allocator()) {}
+  btree(const btree &other, const allocator_type &alloc)
+      : btree(other.key_comp(), alloc) {
+    copy_or_move_values_in_order(other);
+  }
   btree(btree &&other) noexcept
       : root_(std::move(other.root_)),
         rightmost_(absl::exchange(other.rightmost_, EmptyNode())),
         size_(absl::exchange(other.size_, 0)) {
     other.mutable_root() = EmptyNode();
   }
+  btree(btree &&other, const allocator_type &alloc)
+      : btree(other.key_comp(), alloc) {
+    if (alloc == other.allocator()) {
+      swap(other);
+    } else {
+      // Move values from `other` one at a time when allocators are different.
+      copy_or_move_values_in_order(other);
+    }
+  }
 
   ~btree() {
     // Put static_asserts in destructor to avoid triggering them before the type
@@ -1851,19 +1865,19 @@ void btree_iterator<N, R, P>::decrement_slow() {
 // btree methods
 template <typename P>
 template <typename Btree>
-void btree<P>::copy_or_move_values_in_order(Btree *other) {
+void btree<P>::copy_or_move_values_in_order(Btree &other) {
   static_assert(std::is_same<btree, Btree>::value ||
                     std::is_same<const btree, Btree>::value,
                 "Btree type must be same or const.");
   assert(empty());
 
   // We can avoid key comparisons because we know the order of the
   // values is the same order we'll store them in.
-  auto iter = other->begin();
-  if (iter == other->end()) return;
+  auto iter = other.begin();
+  if (iter == other.end()) return;
   insert_multi(maybe_move_from_iterator(iter));
   ++iter;
-  for (; iter != other->end(); ++iter) {
+  for (; iter != other.end(); ++iter) {
     // If the btree is not empty, we can just insert the new value at the end
     // of the tree.
     internal_emplace(end(), maybe_move_from_iterator(iter));
@@ -1901,16 +1915,6 @@ constexpr bool btree<P>::static_assert_validation() {
   return true;
 }
 
-template <typename P>
-btree<P>::btree(const key_compare &comp, const allocator_type &alloc)
-    : root_(comp, alloc, EmptyNode()), rightmost_(EmptyNode()), size_(0) {}
-
-template <typename P>
-btree<P>::btree(const btree &other)
-    : btree(other.key_comp(), other.allocator()) {
-  copy_or_move_values_in_order(&other);
-}
-
 template <typename P>
 template <typename K>
 auto btree<P>::equal_range(const K &key) -> std::pair<iterator, iterator> {
@@ -2068,7 +2072,7 @@ auto btree<P>::operator=(const btree &other) -> btree & {
       *mutable_allocator() = other.allocator();
     }
 
-    copy_or_move_values_in_order(&other);
+    copy_or_move_values_in_order(other);
   }
   return *this;
 }
@@ -2098,7 +2102,7 @@ auto btree<P>::operator=(btree &&other) noexcept -> btree & {
         // comparator while moving the values so we can't swap the key
         // comparators.
         *mutable_key_comp() = other.key_comp();
-        copy_or_move_values_in_order(&other);
+        copy_or_move_values_in_order(other);
       }
     }
   }

absl/container/internal/btree_container.h

@@ -23,6 +23,7 @@
 #include "absl/base/internal/throw_delegate.h"
 #include "absl/container/internal/btree.h"  // IWYU pragma: export
 #include "absl/container/internal/common.h"
+#include "absl/memory/memory.h"
 #include "absl/meta/type_traits.h"
 
 namespace absl {
@@ -68,8 +69,21 @@ class btree_container {
   explicit btree_container(const key_compare &comp,
                            const allocator_type &alloc = allocator_type())
       : tree_(comp, alloc) {}
-  btree_container(const btree_container &other) = default;
-  btree_container(btree_container &&other) noexcept = default;
+  explicit btree_container(const allocator_type &alloc)
+      : tree_(key_compare(), alloc) {}
+
+  btree_container(const btree_container &other)
+      : btree_container(other, absl::allocator_traits<allocator_type>::
+                                   select_on_container_copy_construction(
+                                       other.get_allocator())) {}
+  btree_container(const btree_container &other, const allocator_type &alloc)
+      : tree_(other.tree_, alloc) {}
+
+  btree_container(btree_container &&other) noexcept(
+      std::is_nothrow_move_constructible<Tree>::value) = default;
+  btree_container(btree_container &&other, const allocator_type &alloc)
+      : tree_(std::move(other.tree_), alloc) {}
+
   btree_container &operator=(const btree_container &other) = default;
   btree_container &operator=(btree_container &&other) noexcept(
       std::is_nothrow_move_assignable<Tree>::value) = default;
@@ -234,20 +248,27 @@ class btree_set_container : public btree_container<Tree> {
   using super_type::super_type;
   btree_set_container() {}
 
-  // Range constructor.
+  // Range constructors.
   template <class InputIterator>
   btree_set_container(InputIterator b, InputIterator e,
                       const key_compare &comp = key_compare(),
                       const allocator_type &alloc = allocator_type())
       : super_type(comp, alloc) {
     insert(b, e);
   }
+  template <class InputIterator>
+  btree_set_container(InputIterator b, InputIterator e,
+                      const allocator_type &alloc)
+      : btree_set_container(b, e, key_compare(), alloc) {}
 
-  // Initializer list constructor.
+  // Initializer list constructors.
   btree_set_container(std::initializer_list<init_type> init,
                       const key_compare &comp = key_compare(),
                       const allocator_type &alloc = allocator_type())
       : btree_set_container(init.begin(), init.end(), comp, alloc) {}
+  btree_set_container(std::initializer_list<init_type> init,
+                      const allocator_type &alloc)
+      : btree_set_container(init.begin(), init.end(), alloc) {}
 
   // Lookup routines.
   template <typename K = key_type>
@@ -535,20 +556,27 @@ class btree_multiset_container : public btree_container<Tree> {
   using super_type::super_type;
   btree_multiset_container() {}
 
-  // Range constructor.
+  // Range constructors.
   template <class InputIterator>
   btree_multiset_container(InputIterator b, InputIterator e,
                            const key_compare &comp = key_compare(),
                            const allocator_type &alloc = allocator_type())
       : super_type(comp, alloc) {
     insert(b, e);
   }
+  template <class InputIterator>
+  btree_multiset_container(InputIterator b, InputIterator e,
+                           const allocator_type &alloc)
+      : btree_multiset_container(b, e, key_compare(), alloc) {}
 
-  // Initializer list constructor.
+  // Initializer list constructors.
   btree_multiset_container(std::initializer_list<init_type> init,
                            const key_compare &comp = key_compare(),
                            const allocator_type &alloc = allocator_type())
       : btree_multiset_container(init.begin(), init.end(), comp, alloc) {}
+  btree_multiset_container(std::initializer_list<init_type> init,
+                           const allocator_type &alloc)
+      : btree_multiset_container(init.begin(), init.end(), alloc) {}
 
   // Lookup routines.
   template <typename K = key_type>