From f38cf91ea7c2cedad9b120bcc40b52b53e82dfcb Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Tue, 14 Feb 2023 20:13:16 -0500
Subject: [PATCH] Add attempt to detect improper usage.

---
 ClockReceiver/JustInTime.hpp | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/ClockReceiver/JustInTime.hpp b/ClockReceiver/JustInTime.hpp
index 040b26e4d..939ff0684 100644
--- a/ClockReceiver/JustInTime.hpp
+++ b/ClockReceiver/JustInTime.hpp
@@ -14,6 +14,8 @@
 #include "ClockingHintSource.hpp"
 #include "ForceInline.hpp"
 
+#include <atomic>
+
 /*!
 	A JustInTimeActor holds (i) an embedded object with a run_for method; and (ii) an amount
 	of time since run_for was last called.
@@ -121,7 +123,13 @@ template <class T, class LocalTimeScale = HalfCycles, int multiplier = 1, int di
 		/// If this object provides sequence points, checks for changes to the next
 		/// sequence point upon deletion of the pointer.
 		[[nodiscard]] forceinline auto operator->() {
+#ifndef NDEBUG
+			assert(!flush_concurrency_check_.test_and_set());
+#endif
 			flush();
+#ifndef NDEBUG
+			flush_concurrency_check_.clear();
+#endif
 			return std::unique_ptr<T, SequencePointAwareDeleter>(&object_, SequencePointAwareDeleter(this));
 		}
 
@@ -130,7 +138,13 @@ template <class T, class LocalTimeScale = HalfCycles, int multiplier = 1, int di
 		/// Despite being const, this will flush the object and, if relevant, update the next sequence point.
 		[[nodiscard]] forceinline auto operator -> () const {
 			auto non_const_this = const_cast<JustInTimeActor<T, LocalTimeScale, multiplier, divider> *>(this);
+#ifndef NDEBUG
+			assert(!non_const_this->flush_concurrency_check_.test_and_set());
+#endif
 			non_const_this->flush();
+#ifndef NDEBUG
+			non_const_this->flush_concurrency_check_.clear();
+#endif
 			return std::unique_ptr<const T, SequencePointAwareDeleter>(&object_, SequencePointAwareDeleter(non_const_this));
 		}
 
@@ -264,6 +278,10 @@ template <class T, class LocalTimeScale = HalfCycles, int multiplier = 1, int di
 		void set_component_prefers_clocking(ClockingHint::Source *, ClockingHint::Preference clocking) {
 			clocking_preference_ = clocking;
 		}
+
+#ifndef NDEBUG
+		std::atomic_flag flush_concurrency_check_{};
+#endif
 };
 
 /*!