3 files changed, 33 insertions, 0 deletions

diff --git a/common/str.cpp b/common/str.cpp
index f60d7d5e93..8ed652f847 100644
--- a/common/str.cpp
+++ b/common/str.cpp
@@ -25,10 +25,36 @@
 #include "common/memorypool.h"
 #include "common/str.h"
 #include "common/util.h"
+#include "common/mutex.h"
 
 namespace Common {
 
 MemoryPool *g_refCountPool = nullptr; // FIXME: This is never freed right now
+MutexRef g_refCountPoolMutex = nullptr;
+
+void lockMemoryPoolMutex() {
+	// The Mutex class can only be used once g_system is set and initialized,
+	// but we may use the String class earlier than that (it is for example
+	// used in the OSystem_POSIX constructor). However in those early stages
+	// we can hope we don't have multiple threads either.
+	if (!g_system || !g_system->backendInitialized())
+		return;
+	if (!g_refCountPoolMutex)
+		g_refCountPoolMutex = g_system->createMutex();
+	g_system->lockMutex(g_refCountPoolMutex);
+}
+
+void unlockMemoryPoolMutex() {
+	if (g_refCountPoolMutex)
+		g_system->unlockMutex(g_refCountPoolMutex);
+}
+
+void String::releaseMemoryPoolMutex() {
+	if (g_refCountPoolMutex){
+		g_system->deleteMutex(g_refCountPoolMutex);
+		g_refCountPoolMutex = nullptr;
+	}
+}
 
 static uint32 computeCapacity(uint32 len) {
 	// By default, for the capacity we use the next multiple of 32
@@ -173,12 +199,14 @@ void String::ensureCapacity(uint32 new_size, bool keep_old) {
 void String::incRefCount() const {
 	assert(!isStorageIntern());
 	if (_extern._refCount == nullptr) {
+		lockMemoryPoolMutex();
 		if (g_refCountPool == nullptr) {
 			g_refCountPool = new MemoryPool(sizeof(int));
 			assert(g_refCountPool);
 		}
 
 		_extern._refCount = (int *)g_refCountPool->allocChunk();
+		unlockMemoryPoolMutex();
 		*_extern._refCount = 2;
 	} else {
 		++(*_extern._refCount);
@@ -196,8 +224,10 @@ void String::decRefCount(int *oldRefCount) {
 		// The ref count reached zero, so we free the string storage
 		// and the ref count storage.
 		if (oldRefCount) {
+			lockMemoryPoolMutex();
 			assert(g_refCountPool);
 			g_refCountPool->freeChunk(oldRefCount);
+			unlockMemoryPoolMutex();
 		}
 		delete[] _str;
 
diff --git a/common/str.h b/common/str.h
index 5ed14b6942..704114b68e 100644
--- a/common/str.h
+++ b/common/str.h
@@ -47,6 +47,8 @@ class String {
 public:
 	static const uint32 npos = 0xFFFFFFFF;
 
+	static void releaseMemoryPoolMutex();
+
 	typedef char          value_type;
 	/**
 	 * Unsigned version of the underlying type. This can be used to cast
diff --git a/common/system.cpp b/common/system.cpp
index 97c8f8520b..c8023c8ec2 100644
--- a/common/system.cpp
+++ b/common/system.cpp
@@ -105,6 +105,7 @@ void OSystem::initBackend() {
 
 void OSystem::destroy() {
 	_backendInitialized = false;
+	Common::String::releaseMemoryPoolMutex();
 	delete this;
 }