Reimplement Mutex with C++'s <mutex>

Main:
- It's now implemented thanks to `<mutex>`. No more platform-specific implementations.
- `BinaryMutex` (non-recursive) is added, as an alternative for special cases.
- Doesn't need allocation/deallocation anymore. It can live in the stack and be part of other classes.
- Because of that, it's methods are now `const` and the inner mutex is `mutable` so it can be easily used in `const` contexts.
- A no-op implementation is provided if `NO_THREADS` is defined. No more need to add `#ifdef NO_THREADS` just for this.
- `MutexLock` now takes a reference. At this point the cases of null `Mutex`es are rare. If you ever need that, just don't use `MutexLock`.
- Thread-safe utilities are therefore simpler now.

Misc.:
- `ScopedMutexLock` is dropped and replaced by `MutexLock`, because they were pretty much the same.
- Every case of lock, do-something, unlock is replaced by `MutexLock` (complex cases where it's not straightfoward are kept as as explicit lock and unlock).
- `ShaderRD` contained an `std::mutex`, which has been replaced by `Mutex`.

3 files changed, 0 insertions, 137 deletions

diff --git a/drivers/unix/mutex_posix.cpp b/drivers/unix/mutex_posix.cpp
deleted file mode 100644
index a9fc12fb06..0000000000
--- a/drivers/unix/mutex_posix.cpp
+++ /dev/null
@@ -1,73 +0,0 @@
-/*************************************************************************/
-/*  mutex_posix.cpp                                                      */
-/*************************************************************************/
-/*                       This file is part of:                           */
-/*                           GODOT ENGINE                                */
-/*                      https://godotengine.org                          */
-/*************************************************************************/
-/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
-/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
-/*                                                                       */
-/* Permission is hereby granted, free of charge, to any person obtaining */
-/* a copy of this software and associated documentation files (the       */
-/* "Software"), to deal in the Software without restriction, including   */
-/* without limitation the rights to use, copy, modify, merge, publish,   */
-/* distribute, sublicense, and/or sell copies of the Software, and to    */
-/* permit persons to whom the Software is furnished to do so, subject to */
-/* the following conditions:                                             */
-/*                                                                       */
-/* The above copyright notice and this permission notice shall be        */
-/* included in all copies or substantial portions of the Software.       */
-/*                                                                       */
-/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
-/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
-/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
-/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
-/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
-/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
-/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
-/*************************************************************************/
-
-#include "mutex_posix.h"
-
-#include "core/os/memory.h"
-
-#if defined(UNIX_ENABLED) || defined(PTHREAD_ENABLED)
-
-void MutexPosix::lock() {
-
-	pthread_mutex_lock(&mutex);
-}
-void MutexPosix::unlock() {
-
-	pthread_mutex_unlock(&mutex);
-}
-Error MutexPosix::try_lock() {
-
-	return (pthread_mutex_trylock(&mutex) == 0) ? OK : ERR_BUSY;
-}
-
-Mutex *MutexPosix::create_func_posix(bool p_recursive) {
-
-	return memnew(MutexPosix(p_recursive));
-}
-
-void MutexPosix::make_default() {
-
-	create_func = create_func_posix;
-}
-
-MutexPosix::MutexPosix(bool p_recursive) {
-
-	pthread_mutexattr_init(&attr);
-	if (p_recursive)
-		pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
-	pthread_mutex_init(&mutex, &attr);
-}
-
-MutexPosix::~MutexPosix() {
-
-	pthread_mutex_destroy(&mutex);
-}
-
-#endif
diff --git a/drivers/unix/mutex_posix.h b/drivers/unix/mutex_posix.h
deleted file mode 100644
index bd67106836..0000000000
--- a/drivers/unix/mutex_posix.h
+++ /dev/null
@@ -1,61 +0,0 @@
-/*************************************************************************/
-/*  mutex_posix.h                                                        */
-/*************************************************************************/
-/*                       This file is part of:                           */
-/*                           GODOT ENGINE                                */
-/*                      https://godotengine.org                          */
-/*************************************************************************/
-/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
-/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
-/*                                                                       */
-/* Permission is hereby granted, free of charge, to any person obtaining */
-/* a copy of this software and associated documentation files (the       */
-/* "Software"), to deal in the Software without restriction, including   */
-/* without limitation the rights to use, copy, modify, merge, publish,   */
-/* distribute, sublicense, and/or sell copies of the Software, and to    */
-/* permit persons to whom the Software is furnished to do so, subject to */
-/* the following conditions:                                             */
-/*                                                                       */
-/* The above copyright notice and this permission notice shall be        */
-/* included in all copies or substantial portions of the Software.       */
-/*                                                                       */
-/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
-/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
-/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
-/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
-/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
-/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
-/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
-/*************************************************************************/
-
-#ifndef MUTEX_POSIX_H
-#define MUTEX_POSIX_H
-
-#if defined(UNIX_ENABLED) || defined(PTHREAD_ENABLED)
-
-#include "core/os/mutex.h"
-
-#include <pthread.h>
-
-class MutexPosix : public Mutex {
-
-	pthread_mutexattr_t attr;
-	pthread_mutex_t mutex;
-
-	static Mutex *create_func_posix(bool p_recursive);
-
-public:
-	virtual void lock();
-	virtual void unlock();
-	virtual Error try_lock();
-
-	static void make_default();
-
-	MutexPosix(bool p_recursive);
-
-	~MutexPosix();
-};
-
-#endif
-
-#endif
diff --git a/drivers/unix/os_unix.cpp b/drivers/unix/os_unix.cpp
index 2d8d37b2f1..1d94b9618d 100644
--- a/drivers/unix/os_unix.cpp
+++ b/drivers/unix/os_unix.cpp
@@ -36,7 +36,6 @@
 #include "core/project_settings.h"
 #include "drivers/unix/dir_access_unix.h"
 #include "drivers/unix/file_access_unix.h"
-#include "drivers/unix/mutex_posix.h"
 #include "drivers/unix/net_socket_posix.h"
 #include "drivers/unix/rw_lock_posix.h"
 #include "drivers/unix/semaphore_posix.h"
@@ -123,14 +122,12 @@ void OS_Unix::initialize_core() {
 #ifdef NO_THREADS
 	ThreadDummy::make_default();
 	SemaphoreDummy::make_default();
-	MutexDummy::make_default();
 	RWLockDummy::make_default();
 #else
 	ThreadPosix::make_default();
 #if !defined(OSX_ENABLED) && !defined(IPHONE_ENABLED)
 	SemaphorePosix::make_default();
 #endif
-	MutexPosix::make_default();
 	RWLockPosix::make_default();
 #endif
 	FileAccess::make_default<FileAccessUnix>(FileAccess::ACCESS_RESOURCES);