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- `ShaderRD` contained an `std::mutex`, which has been replaced by `Mutex`.

1 files changed, 11 insertions, 50 deletions

diff --git a/modules/gdnative/nativescript/nativescript.cpp b/modules/gdnative/nativescript/nativescript.cpp
index 8240ae2f83..0ec6ad71d9 100644
--- a/modules/gdnative/nativescript/nativescript.cpp
+++ b/modules/gdnative/nativescript/nativescript.cpp
@@ -222,15 +222,11 @@ ScriptInstance *NativeScript::instance_create(Object *p_this) {
 	nsi->userdata = script_data->create_func.create_func((godot_object *)p_this, script_data->create_func.method_data);
 #endif
 
-#ifndef NO_THREADS
-	owners_lock->lock();
-#endif
-
-	instance_owners.insert(p_this);
+	{
+		MutexLock lock(owners_lock);
 
-#ifndef NO_THREADS
-	owners_lock->unlock();
-#endif
+		instance_owners.insert(p_this);
+	}
 
 	return nsi;
 }
@@ -782,17 +778,10 @@ NativeScript::NativeScript() {
 	library = Ref<GDNative>();
 	lib_path = "";
 	class_name = "";
-#ifndef NO_THREADS
-	owners_lock = Mutex::create();
-#endif
 }
 
 NativeScript::~NativeScript() {
 	NSL->unregister_script(this);
-
-#ifndef NO_THREADS
-	memdelete(owners_lock);
-#endif
 }
 
 #define GET_SCRIPT_DESC() script->get_script_desc()
@@ -1140,16 +1129,9 @@ NativeScriptInstance::~NativeScriptInstance() {
 	script_data->destroy_func.destroy_func((godot_object *)owner, script_data->destroy_func.method_data, userdata);
 
 	if (owner) {
-
-#ifndef NO_THREADS
-		script->owners_lock->lock();
-#endif
+		MutexLock lock(script->owners_lock);
 
 		script->instance_owners.erase(owner);
-
-#ifndef NO_THREADS
-		script->owners_lock->unlock();
-#endif
 	}
 }
 
@@ -1246,7 +1228,6 @@ NativeScriptLanguage::NativeScriptLanguage() {
 	NativeScriptLanguage::singleton = this;
 #ifndef NO_THREADS
 	has_objects_to_register = false;
-	mutex = Mutex::create();
 #endif
 
 #ifdef DEBUG_ENABLED
@@ -1283,10 +1264,6 @@ NativeScriptLanguage::~NativeScriptLanguage() {
 	NSL->library_classes.clear();
 	NSL->library_gdnatives.clear();
 	NSL->library_script_users.clear();
-
-#ifndef NO_THREADS
-	memdelete(mutex);
-#endif
 }
 
 String NativeScriptLanguage::get_name() const {
@@ -1413,9 +1390,7 @@ void NativeScriptLanguage::get_public_constants(List<Pair<String, Variant> > *p_
 
 void NativeScriptLanguage::profiling_start() {
 #ifdef DEBUG_ENABLED
-#ifndef NO_THREADS
 	MutexLock lock(mutex);
-#endif
 
 	profile_data.clear();
 	profiling = true;
@@ -1424,9 +1399,7 @@ void NativeScriptLanguage::profiling_start() {
 
 void NativeScriptLanguage::profiling_stop() {
 #ifdef DEBUG_ENABLED
-#ifndef NO_THREADS
 	MutexLock lock(mutex);
-#endif
 
 	profiling = false;
 #endif
@@ -1434,9 +1407,8 @@ void NativeScriptLanguage::profiling_stop() {
 
 int NativeScriptLanguage::profiling_get_accumulated_data(ProfilingInfo *p_info_arr, int p_info_max) {
 #ifdef DEBUG_ENABLED
-#ifndef NO_THREADS
 	MutexLock lock(mutex);
-#endif
+
 	int current = 0;
 
 	for (Map<StringName, ProfileData>::Element *d = profile_data.front(); d; d = d->next()) {
@@ -1458,9 +1430,8 @@ int NativeScriptLanguage::profiling_get_accumulated_data(ProfilingInfo *p_info_a
 
 int NativeScriptLanguage::profiling_get_frame_data(ProfilingInfo *p_info_arr, int p_info_max) {
 #ifdef DEBUG_ENABLED
-#ifndef NO_THREADS
 	MutexLock lock(mutex);
-#endif
+
 	int current = 0;
 
 	for (Map<StringName, ProfileData>::Element *d = profile_data.front(); d; d = d->next()) {
@@ -1484,9 +1455,7 @@ int NativeScriptLanguage::profiling_get_frame_data(ProfilingInfo *p_info_arr, in
 
 void NativeScriptLanguage::profiling_add_data(StringName p_signature, uint64_t p_time) {
 #ifdef DEBUG_ENABLED
-#ifndef NO_THREADS
 	MutexLock lock(mutex);
-#endif
 
 	Map<StringName, ProfileData>::Element *d = profile_data.find(p_signature);
 	if (d) {
@@ -1705,9 +1674,8 @@ void NativeScriptLanguage::defer_init_library(Ref<GDNativeLibrary> lib, NativeSc
 #endif
 
 void NativeScriptLanguage::init_library(const Ref<GDNativeLibrary> &lib) {
-#ifndef NO_THREADS
 	MutexLock lock(mutex);
-#endif
+
 	// See if this library was "registered" already.
 	const String &lib_path = lib->get_current_library_path();
 	ERR_FAIL_COND_MSG(lib_path.length() == 0, lib->get_name() + " does not have a library for the current platform.");
@@ -1743,16 +1711,14 @@ void NativeScriptLanguage::init_library(const Ref<GDNativeLibrary> &lib) {
 }
 
 void NativeScriptLanguage::register_script(NativeScript *script) {
-#ifndef NO_THREADS
 	MutexLock lock(mutex);
-#endif
+
 	library_script_users[script->lib_path].insert(script);
 }
 
 void NativeScriptLanguage::unregister_script(NativeScript *script) {
-#ifndef NO_THREADS
 	MutexLock lock(mutex);
-#endif
+
 	Map<String, Set<NativeScript *> >::Element *S = library_script_users.find(script->lib_path);
 	if (S) {
 		S->get().erase(script);
@@ -1803,9 +1769,7 @@ void NativeScriptLanguage::frame() {
 
 #ifdef DEBUG_ENABLED
 	{
-#ifndef NO_THREADS
 		MutexLock lock(mutex);
-#endif
 
 		for (Map<StringName, ProfileData>::Element *d = profile_data.front(); d; d = d->next()) {
 			d->get().last_frame_call_count = d->get().frame_call_count;
@@ -1867,9 +1831,7 @@ void NativeReloadNode::_notification(int p_what) {
 
 			if (unloaded)
 				break;
-#ifndef NO_THREADS
 			MutexLock lock(NSL->mutex);
-#endif
 			NSL->_unload_stuff(true);
 
 			for (Map<String, Ref<GDNative> >::Element *L = NSL->library_gdnatives.front(); L; L = L->next()) {
@@ -1904,9 +1866,8 @@ void NativeReloadNode::_notification(int p_what) {
 
 			if (!unloaded)
 				break;
-#ifndef NO_THREADS
 			MutexLock lock(NSL->mutex);
-#endif
+
 			Set<StringName> libs_to_remove;
 			for (Map<String, Ref<GDNative> >::Element *L = NSL->library_gdnatives.front(); L; L = L->next()) {