From d96179be75ecc344bf71f2d1ffa60f6847d6425e Mon Sep 17 00:00:00 2001
From: Fabio Alessandrelli <fabio.alessandrelli@gmail.com>
Date: Sun, 8 Mar 2020 00:06:57 +0100
Subject: [PATCH] Fix mutex when building with no threads.

---
 core/os/mutex.cpp |  4 ++++
 core/os/mutex.h   | 26 +++++++++++++++++---------
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/core/os/mutex.cpp b/core/os/mutex.cpp
index 74c308f6467..97297dca286 100644
--- a/core/os/mutex.cpp
+++ b/core/os/mutex.cpp
@@ -40,7 +40,11 @@ void _global_unlock() {
 	_global_mutex.unlock();
 }
 
+#ifndef NO_THREADS
+
 template class MutexImpl<std::recursive_mutex>;
 template class MutexImpl<std::mutex>;
 template class MutexLock<MutexImpl<std::recursive_mutex> >;
 template class MutexLock<MutexImpl<std::mutex> >;
+
+#endif
diff --git a/core/os/mutex.h b/core/os/mutex.h
index 8d7b378d601..9033f0cb060 100644
--- a/core/os/mutex.h
+++ b/core/os/mutex.h
@@ -71,9 +71,22 @@ public:
 	}
 };
 
+using Mutex = MutexImpl<std::recursive_mutex>; // Recursive, for general use
+using BinaryMutex = MutexImpl<std::mutex>; // Non-recursive, handle with care
+
+extern template class MutexImpl<std::recursive_mutex>;
+extern template class MutexImpl<std::mutex>;
+extern template class MutexLock<MutexImpl<std::recursive_mutex> >;
+extern template class MutexLock<MutexImpl<std::mutex> >;
+
 #else
 
-template <class StdMutexType>
+class FakeMutex {
+
+	FakeMutex(){};
+};
+
+template <class MutexT>
 class MutexImpl {
 public:
 	_ALWAYS_INLINE_ void lock() const {}
@@ -87,14 +100,9 @@ public:
 	explicit MutexLock(const MutexT &p_mutex) {}
 };
 
+using Mutex = MutexImpl<FakeMutex>;
+using BinaryMutex = MutexImpl<FakeMutex>; // Non-recursive, handle with care
+
 #endif // !NO_THREADS
 
-using Mutex = MutexImpl<std::recursive_mutex>; // Recursive, for general use
-using BinaryMutex = MutexImpl<std::mutex>; // Non-recursive, handle with care
-
-extern template class MutexImpl<std::recursive_mutex>;
-extern template class MutexImpl<std::mutex>;
-extern template class MutexLock<MutexImpl<std::recursive_mutex> >;
-extern template class MutexLock<MutexImpl<std::mutex> >;
-
 #endif