From 5a746a6b1066a3b59dd75f221ed08a42876f3e00 Mon Sep 17 00:00:00 2001
From: John Fultz <jfultz@wolfram.com>
Date: Sun, 21 Jul 2019 01:59:37 -0700
Subject: Make the PRNG thread-safe.

Turns out that the C++ PRNGs aren't thread-safe.  So lock
calls to m_mersenneTwisterRng.  Makes Thread Sanitizer happy.
---
 datamanager.cpp | 3 +++
 datamanager.h   | 4 +++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/datamanager.cpp b/datamanager.cpp
index 2dea169..55d1166 100644
--- a/datamanager.cpp
+++ b/datamanager.cpp
@@ -178,15 +178,18 @@ string DataManager::makeDataFilename(const string &subDirectory, const string &f
 
 void DataManager::seedRandomNumbers(unsigned int seed)
 {
+	lock_guard<mutex> lock(m_RngMutex);
 	m_mersenneTwisterRng.seed(seed);
 }
 
 void DataManager::seedRandomNumbers(seed_seq& seed)
 {
+	lock_guard<mutex> lock(m_RngMutex);
 	m_mersenneTwisterRng.seed(seed);
 }
 
 int DataManager::randomInteger(int low, int high)
 {
+	lock_guard<mutex> lock(m_RngMutex);
 	return uniform_int_distribution<>(low, high)(m_mersenneTwisterRng);
 }
diff --git a/datamanager.h b/datamanager.h
index 92ebfd9..219a500 100644
--- a/datamanager.h
+++ b/datamanager.h
@@ -19,8 +19,9 @@
 #ifndef QUACKLE_DATAMANAGER_H
 #define QUACKLE_DATAMANAGER_H
 
-#include <string>
+#include <mutex>
 #include <random>
+#include <string>
 
 #include "playerlist.h"
 
@@ -148,6 +149,7 @@ private:
 	PlayerList m_computerPlayers;
 
 	mt19937_64 m_mersenneTwisterRng;
+	mutex m_RngMutex;
 };
 
 inline DataManager *DataManager::self()
-- 
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