From a17886b7060aa0c24bf7ed6a744808c3bc243f36 Mon Sep 17 00:00:00 2001
From: rexy712 <rexy712@protonmail.com>
Date: Fri, 18 Jun 2021 21:46:55 -0700
Subject: [PATCH] Fix bug in mpmc_queue causing objects larger than cacheline
 to fail during compilation

---
 include/rexy/mpmc_queue.hpp | 3 ++-
 include/rexy/mpmc_queue.tpp | 5 +++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/rexy/mpmc_queue.hpp b/include/rexy/mpmc_queue.hpp
index 66b3dd8..60fb11c 100644
--- a/include/rexy/mpmc_queue.hpp
+++ b/include/rexy/mpmc_queue.hpp
@@ -24,6 +24,7 @@
 #include <atomic> //atomic (duh)
 
 #include "rexy.hpp"
+#include "utility.hpp" //min
 
 #ifdef __cpp_lib_hardware_interference_size
 #include <new> //hardware_destructive_interference_size
@@ -72,7 +73,7 @@ namespace rexy{
 			alignas(cacheline_size) std::atomic<size_type> m_turn = {0};
 			alignas(alignof(value_type)) unsigned char m_data[sizeof(value_type)] = {};
 			//ensure no false sharing with following data
-			char cachline_padding[cacheline_size - (sizeof(m_data) + sizeof(m_turn))];
+			char cachline_padding[cacheline_size - ((sizeof(m_data) + sizeof(m_turn)) % cacheline_size)];
 		public:
 			slot() = default;
 			slot(const slot& s);
diff --git a/include/rexy/mpmc_queue.tpp b/include/rexy/mpmc_queue.tpp
index bdc7230..ec5fa78 100644
--- a/include/rexy/mpmc_queue.tpp
+++ b/include/rexy/mpmc_queue.tpp
@@ -128,12 +128,13 @@ namespace rexy{
 	void mpmc_queue<T>::emplace(Args&&... args){
 		const size_type head = m_head.fetch_add(1, std::memory_order_seq_cst);
 		slot& s = m_slots[head % m_slots.capacity()];
+		const size_type rot_count = rotation_cnt(head);
 		//lsb is in-use flag. wait for it to be 0
-		while(rotation_cnt(head) << 1 != s.turn().load(std::memory_order_acquire));
+		while(rot_count << 1 != s.turn().load(std::memory_order_acquire));
 
 		s.construct(std::forward<Args>(args)...);
 		//set in-use flag
-		s.turn().store((rotation_cnt(head) << 1) + 1, std::memory_order_release);
+		s.turn().store((rot_count << 1) + 1, std::memory_order_release);
 	}
 	template<class T>
 	template<class... Args>