bug #1598: Let MaxSizeVector respect alignment of objects and add a unit test

Also revert 8b3d9ed081fc5d4870290649853b19cb5179546e

1 files changed, 3 insertions, 4 deletions

diff --git a/unsupported/Eigen/CXX11/src/ThreadPool/EventCount.h b/unsupported/Eigen/CXX11/src/ThreadPool/EventCount.h
index 2cac2d0f1..22c952ae1 100644
--- a/unsupported/Eigen/CXX11/src/ThreadPool/EventCount.h
+++ b/unsupported/Eigen/CXX11/src/ThreadPool/EventCount.h
@@ -169,7 +169,9 @@ class EventCount {
 
   class Waiter {
     friend class EventCount;
-    std::atomic<Waiter*> next;
+    // Align to 128 byte boundary to prevent false sharing with other Waiter
+    // objects in the same vector.
+    EIGEN_ALIGN_TO_BOUNDARY(128) std::atomic<Waiter*> next;
     std::mutex mu;
     std::condition_variable cv;
     uint64_t epoch;
@@ -179,9 +181,6 @@ class EventCount {
       kWaiting,
       kSignaled,
     };
-    // Pad past 128 byte boundary to prevent false sharing with other Waiter
-    // objects in the same vector.
-    char pad_[128];
   };
 
  private: