From f2499953c0d3b3c4ae4632d1c6b8785ea5b9b22f Mon Sep 17 00:00:00 2001
From: MerryMage <MerryMage@users.noreply.github.com>
Date: Tue, 7 Apr 2020 20:49:46 +0100
Subject: [PATCH] travis: Update xcode

Update to 10.2 (required for CTAD to work correctly)
---
 .travis.yml              |  2 +-
 src/common/ring_buffer.h | 21 +++++++++++++++++----
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index ba721464f..f1ddde4de 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -32,7 +32,7 @@ matrix:
     - os: osx
       env: NAME="macos build"
       sudo: false
-      osx_image: xcode10
+      osx_image: xcode10.2
       install: "./.travis/macos/deps.sh"
       script: "./.travis/macos/build.sh"
       after_success: "./.travis/macos/upload.sh"
diff --git a/src/common/ring_buffer.h b/src/common/ring_buffer.h
index 428d3095f..bb94b898b 100644
--- a/src/common/ring_buffer.h
+++ b/src/common/ring_buffer.h
@@ -9,6 +9,7 @@
 #include <atomic>
 #include <cstddef>
 #include <cstring>
+#include <new>
 #include <type_traits>
 #include <vector>
 #include "common/common_types.h"
@@ -29,7 +30,7 @@ class RingBuffer {
     static_assert(capacity < std::numeric_limits<std::size_t>::max() / 2 / granularity);
     static_assert((capacity & (capacity - 1)) == 0, "capacity must be a power of two");
     // Ensure lock-free.
-    static_assert(std::atomic<std::size_t>::is_always_lock_free);
+    static_assert(std::atomic_size_t::is_always_lock_free);
 
 public:
     /// Pushes slots into the ring buffer
@@ -100,10 +101,22 @@ public:
     }
 
 private:
-    // It is important to align the below variables for performance reasons:
+    // It is important to separate the below atomics for performance reasons:
     // Having them on the same cache-line would result in false-sharing between them.
-    alignas(128) std::atomic<std::size_t> m_read_index{0};
-    alignas(128) std::atomic<std::size_t> m_write_index{0};
+    // TODO: Remove this ifdef whenever clang and GCC support
+    //       std::hardware_destructive_interference_size.
+#if defined(_MSC_VER) && _MSC_VER >= 1911
+    static constexpr std::size_t padding_size =
+        std::hardware_destructive_interference_size - sizeof(std::atomic_size_t);
+#else
+    static constexpr std::size_t padding_size = 128 - sizeof(std::atomic_size_t);
+#endif
+
+    std::atomic_size_t m_read_index{0};
+    char padding1[padding_size];
+
+    std::atomic_size_t m_write_index{0};
+    char padding2[padding_size];
 
     std::array<T, granularity * capacity> m_data;
 };