Export of internal Abseil changes

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90ecacd2a3db96ee64ef23af37a80fad404e2b32 by Gennadiy Rozental <rogeeff@google.com>:

Fixes MSVC regression by making MSVC version of class Flag into an aggregate type.

PiperOrigin-RevId: 277767054

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018f3b040df51d91a988fa146fee163721e605e9 by Abseil Team <absl-team@google.com>:

Change libstdc++ lacking std::unique_ptr check from a gcc version check to based on feature macros.

PiperOrigin-RevId: 277736042

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475844775ae343e2414318f08549ee3fa6676a8d by CJ Johnson <johnsoncj@google.com>:

Pass allocator_type through allocator_traits before extracting the typedefs

PiperOrigin-RevId: 277730393

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d843bc4bc30bf5b11af76db8beda8634b6111a62 by Abseil Team <absl-team@google.com>:

Convert the Waiter::Init() method to the default constructor and define
a destructor for the Waiter class.

Use placement new and delete with Waiter objects.

PiperOrigin-RevId: 277728823

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1ba6edf421dd2dfe13c55970a03c99592cb6677d by Derek Mauro <dmauro@google.com>:

Use lowercase spelling for include of dbghelp.h
When cross-compiling under MinGW this is important

PiperOrigin-RevId: 277629783

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cfc662a6fa357a84ddda8037156c7f26cee40c36 by Abseil Team <absl-team@google.com>:

Don't use atomic ops on waiter and wakeup counts in WIN32 waiter mode.

Port the new CONDVAR waiter mode code in CL 277366017 to the WIN32
waiter mode.

PiperOrigin-RevId: 277603611

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833106542e61fa0832900adf3c1b2afc6890b94b by Abseil Team <absl-team@google.com>:

Add the PerThreadSem::Destroy() method.

For ABSL_WAITER_MODE_CONDVAR or ABSL_WAITER_MODE_SEM,
PerThreadSem::Destroy() is used to destroy the pthread mutex and
condition variable or the POSIX semaphore.
PiperOrigin-RevId: 277586675

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7814da4a59106cf1e0e4db1a31b9592ebbd2094b by Samuel Benzaquen <sbenza@google.com>:

Enable the assertion in the iterator's operator* and operator->

PiperOrigin-RevId: 277563401
GitOrigin-RevId: 90ecacd2a3db96ee64ef23af37a80fad404e2b32
Change-Id: Ib19be3680da74f0b94055c9039115ec6bcaea7b0

1 files changed, 13 insertions, 14 deletions

diff --git a/absl/synchronization/internal/waiter.h b/absl/synchronization/internal/waiter.h
index c238970..cac81d5 100644
--- a/absl/synchronization/internal/waiter.h
+++ b/absl/synchronization/internal/waiter.h
@@ -58,14 +58,15 @@ namespace synchronization_internal {
 // Waiter is an OS-specific semaphore.
 class Waiter {
  public:
-  // No constructor, instances use the reserved space in ThreadIdentity.
-  // All initialization logic belongs in `Init()`.
-  Waiter() = delete;
+  // Prepare any data to track waits.
+  Waiter();
+
+  // Not copyable or movable
   Waiter(const Waiter&) = delete;
   Waiter& operator=(const Waiter&) = delete;
 
-  // Prepare any data to track waits.
-  void Init();
+  // Destroy any data to track waits.
+  ~Waiter();
 
   // Blocks the calling thread until a matching call to `Post()` or
   // `t` has passed. Returns `true` if woken (`Post()` called),
@@ -122,13 +123,8 @@ class Waiter {
   std::atomic<int> wakeups_;
 
 #elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_WIN32
-  // The Windows API has lots of choices for synchronization
-  // primivitives.  We are using SRWLOCK and CONDITION_VARIABLE
-  // because they don't require a destructor to release system
-  // resources.
-  //
-  // However, we can't include Windows.h in our headers, so we use aligned
-  // storage buffers to define the storage.
+  // We can't include Windows.h in our headers, so we use aligned storage
+  // buffers to define the storage of SRWLOCK and CONDITION_VARIABLE.
   using SRWLockStorage =
       typename std::aligned_storage<sizeof(void*), alignof(void*)>::type;
   using ConditionVariableStorage =
@@ -138,10 +134,13 @@ class Waiter {
   // condition variable storage once the types are complete.
   class WinHelper;
 
+  // REQUIRES: WinHelper::GetLock(this) must be held.
+  void InternalCondVarPoke();
+
   SRWLockStorage mu_storage_;
   ConditionVariableStorage cv_storage_;
-  std::atomic<int> waiter_count_;
-  std::atomic<int> wakeup_count_;
+  int waiter_count_;
+  int wakeup_count_;
 
 #else
   #error Unknown ABSL_WAITER_MODE