Index: binaries/system/readme.txt
===================================================================
--- binaries/system/readme.txt
+++ binaries/system/readme.txt
@@ -64,6 +64,8 @@
 -rejointest=N       simulates a rejoin and checks simulation state each turn for serialization
                     errors; this is similar to a serialization test but much faster and
                     less complete. It should be enough for debugging most rejoin OOSes.
+-unique-logs        adds unix timestamp and process id to the filename of mainlog.html, interestinglog.html
+                    and oos_dump.txt to prevent the files from becoming overwritten by another process.
 
 Windows-specific:
 -wQpcTscSafe        allow timing via QueryPerformanceCounter despite the fact
Index: source/main.cpp
===================================================================
--- source/main.cpp
+++ source/main.cpp
@@ -83,7 +83,13 @@
 #include <unistd.h> // geteuid
 #endif // OS_UNIX
 
+#if MSC_VERSION
+#include <process.h>
+#define getpid _getpid // Use the non-deprecated function name
+#endif
+
 extern bool g_GameRestarted;
+extern CStrW g_UniqueLogPostfix;
 
 void kill_mainloop();
 
@@ -463,6 +469,13 @@
 		return;
 	}
 
+	if (args.Has("unique-logs"))
+	{
+		std::wstringstream postfix;
+		postfix << L"_" << std::time(nullptr) << L"_" << getpid();
+		g_UniqueLogPostfix = postfix.str();
+	}
+
 	const bool isVisualReplay = args.Has("replay-visual");
 	const bool isNonVisualReplay = args.Has("replay");
 	const bool isNonVisual = args.Has("autostart-nonvisual");
Index: source/network/NetClientTurnManager.cpp
===================================================================
--- source/network/NetClientTurnManager.cpp
+++ source/network/NetClientTurnManager.cpp
@@ -33,6 +33,8 @@
 #define NETCLIENTTURN_LOG(...)
 #endif
 
+extern CStrW g_UniqueLogPostfix;
+
 CNetClientTurnManager::CNetClientTurnManager(CSimulation2& simulation, CNetClient& client, int clientId, IReplayLogger& replay)
 	: CTurnManager(simulation, DEFAULT_TURN_LENGTH_MP, clientId, replay), m_NetClient(client)
 {
@@ -116,8 +118,10 @@
 	std::string hash;
 	ENSURE(m_Simulation2.ComputeStateHash(hash, !TurnNeedsFullHash(turn)));
 
-	OsPath path = psLogDir() / "oos_dump.txt";
-	std::ofstream file (OsString(path).c_str(), std::ofstream::out | std::ofstream::trunc);
+	CStrW oosdumpName = L"oos_dump" + g_UniqueLogPostfix + L".txt";
+
+	OsPath oosdumpPath(psLogDir() / oosdumpName);
+	std::ofstream file (OsString(oosdumpPath).c_str(), std::ofstream::out | std::ofstream::trunc);
 	m_Simulation2.DumpDebugState(file);
 	file.close();
 
@@ -131,7 +135,7 @@
 		playerNamesStrings.push_back(name);
 	}
 
-	LOGERROR("Out-Of-Sync on turn %d\nPlayers: %s\nDumping state to %s", turn, playerNamesString.str().c_str(), path.string8());
+	LOGERROR("Out-Of-Sync on turn %d\nPlayers: %s\nDumping state to %s", turn, playerNamesString.str().c_str(), oosdumpPath.string8());
 
 	ScriptInterface& scriptInterface = m_NetClient.GetScriptInterface();
 	JSContext* cx = scriptInterface.GetContext();
@@ -143,7 +147,7 @@
 	scriptInterface.SetProperty(msg, "players", playerNamesStrings);
 	scriptInterface.SetProperty(msg, "expectedHash", expectedHashHex);
 	scriptInterface.SetProperty(msg, "hash", Hexify(hash));
-	scriptInterface.SetProperty(msg, "path_oos_dump", path.string8());
+	scriptInterface.SetProperty(msg, "path_oos_dump", oosdumpPath.string8());
 	scriptInterface.SetProperty(msg, "path_replay", m_Replay.GetDirectory().string8());
 	m_NetClient.PushGuiMessage(msg);
 }
Index: source/ps/CLogger.cpp
===================================================================
--- source/ps/CLogger.cpp
+++ source/ps/CLogger.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2016 Wildfire Games.
+/* Copyright (C) 2017 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -34,6 +34,7 @@
 
 #include <boost/algorithm/string/replace.hpp>
 
+CStrW g_UniqueLogPostfix = L"";
 static const double RENDER_TIMEOUT = 10.0; // seconds before messages are deleted
 static const double RENDER_TIMEOUT_RATE = 10.0; // number of timed-out messages deleted per second
 static const size_t RENDER_LIMIT = 20; // maximum messages on screen at once
@@ -65,10 +66,15 @@
 
 CLogger::CLogger()
 {
-	OsPath mainlogPath(psLogDir()/"mainlog.html");
+	CStrW mainlogName = L"mainlog" + g_UniqueLogPostfix + L".html";
+
+	OsPath mainlogPath(psLogDir()/mainlogName);
 	m_MainLog = new std::ofstream(OsString(mainlogPath).c_str(), std::ofstream::out | std::ofstream::trunc);
+	debug_printf("Writing the mainlog at %s\n", mainlogPath.string8().c_str());
+
+	CStrW interestinglogName = L"interestinglog" + g_UniqueLogPostfix + L".html";
 
-	OsPath interestinglogPath(psLogDir()/"interestinglog.html");
+	OsPath interestinglogPath(psLogDir() / interestinglogName);
 	m_InterestingLog = new std::ofstream(OsString(interestinglogPath).c_str(), std::ofstream::out | std::ofstream::trunc);
 
 	m_OwnsStreams = true;