Remove NO_THREADS fallback code, Godot 4 requires thread support

This also removes `OS::can_use_threads` from the public API since it's always
true.

3 files changed, 1 insertions, 299 deletions

diff --git a/core/templates/cowdata.h b/core/templates/cowdata.h
index f98b2308c9..1482e3eef1 100644
--- a/core/templates/cowdata.h
+++ b/core/templates/cowdata.h
@@ -46,9 +46,7 @@ class CharString;
 template <class T, class V>
 class VMap;
 
-#if !defined(NO_THREADS)
 SAFE_NUMERIC_TYPE_PUN_GUARANTEES(uint32_t)
-#endif
 
 // Silence a false positive warning (see GH-52119).
 #if defined(__GNUC__) && !defined(__clang__)
diff --git a/core/templates/safe_list.h b/core/templates/safe_list.h
index e850f3bd5e..95e8ca1a14 100644
--- a/core/templates/safe_list.h
+++ b/core/templates/safe_list.h
@@ -33,11 +33,9 @@
 
 #include "core/os/memory.h"
 #include "core/typedefs.h"
-#include <functional>
-
-#if !defined(NO_THREADS)
 
 #include <atomic>
+#include <functional>
 #include <type_traits>
 
 // Design goals for these classes:
@@ -239,159 +237,4 @@ public:
 	}
 };
 
-#else // NO_THREADS
-
-// Effectively the same structure without the atomics. It's probably possible to simplify it but the semantics shouldn't differ greatly.
-template <class T, class A = DefaultAllocator>
-class SafeList {
-	struct SafeListNode {
-		SafeListNode *next = nullptr;
-
-		// If the node is logically deleted, this pointer will typically point to the previous list item in time that was also logically deleted.
-		SafeListNode *graveyard_next = nullptr;
-
-		std::function<void(T)> deletion_fn = [](T t) { return; };
-
-		T val;
-	};
-
-	SafeListNode *head = nullptr;
-	SafeListNode *graveyard_head = nullptr;
-
-	unsigned int active_iterator_count = 0;
-
-public:
-	class Iterator {
-		friend class SafeList;
-
-		SafeListNode *cursor = nullptr;
-		SafeList *list = nullptr;
-
-	public:
-		Iterator(SafeListNode *p_cursor, SafeList *p_list) :
-				cursor(p_cursor), list(p_list) {
-			list->active_iterator_count++;
-		}
-
-		~Iterator() {
-			list->active_iterator_count--;
-		}
-
-		T &operator*() {
-			return cursor->val;
-		}
-
-		Iterator &operator++() {
-			cursor = cursor->next;
-			return *this;
-		}
-
-		// These two operators are mostly useful for comparisons to nullptr.
-		bool operator==(const void *p_other) const {
-			return cursor == p_other;
-		}
-
-		bool operator!=(const void *p_other) const {
-			return cursor != p_other;
-		}
-
-		// These two allow easy range-based for loops.
-		bool operator==(const Iterator &p_other) const {
-			return cursor == p_other.cursor;
-		}
-
-		bool operator!=(const Iterator &p_other) const {
-			return cursor != p_other.cursor;
-		}
-	};
-
-public:
-	// Calling this will cause an allocation.
-	void insert(T p_value) {
-		SafeListNode *new_node = memnew_allocator(SafeListNode, A);
-		new_node->val = p_value;
-		new_node->next = head;
-		head = new_node;
-	}
-
-	Iterator find(T p_value) {
-		for (Iterator it = begin(); it != end(); ++it) {
-			if (*it == p_value) {
-				return it;
-			}
-		}
-		return end();
-	}
-
-	void erase(T p_value, std::function<void(T)> p_deletion_fn) {
-		erase(find(p_value), p_deletion_fn);
-	}
-
-	void erase(T p_value) {
-		erase(find(p_value), [](T t) { return; });
-	}
-
-	void erase(Iterator p_iterator, std::function<void(T)> p_deletion_fn) {
-		p_iterator.cursor->deletion_fn = p_deletion_fn;
-		erase(p_iterator);
-	}
-
-	void erase(Iterator p_iterator) {
-		Iterator prev = begin();
-		for (; prev != end(); ++prev) {
-			if (prev.cursor && prev.cursor->next == p_iterator.cursor) {
-				break;
-			}
-		}
-		if (prev == end()) {
-			// Not in the list, nothing to do.
-			return;
-		}
-		// First, remove the node from the list.
-		prev.cursor->next = p_iterator.cursor->next;
-
-		// Then queue it for deletion by putting it in the node graveyard. Don't touch `next` because an iterator might still be pointing at this node.
-		p_iterator.cursor->graveyard_next = graveyard_head;
-		graveyard_head = p_iterator.cursor;
-	}
-
-	Iterator begin() {
-		return Iterator(head, this);
-	}
-
-	Iterator end() {
-		return Iterator(nullptr, this);
-	}
-
-	// Calling this will cause zero to many deallocations.
-	bool maybe_cleanup() {
-		SafeListNode *cursor = graveyard_head;
-		if (active_iterator_count != 0) {
-			// It's not safe to clean up with an active iterator, because that iterator could be pointing to an element that we want to delete.
-			return false;
-		}
-		graveyard_head = nullptr;
-		// Our graveyard list is now unreachable by any active iterators, detached from the main graveyard head and ready for deletion.
-		while (cursor) {
-			SafeListNode *tmp = cursor;
-			cursor = cursor->next;
-			tmp->deletion_fn(tmp->val);
-			memdelete_allocator<SafeListNode, A>(tmp);
-		}
-		return true;
-	}
-
-	~SafeList() {
-#ifdef DEBUG_ENABLED
-		if (!maybe_cleanup()) {
-			ERR_PRINT("There are still iterators around when destructing a SafeList. Memory will be leaked. This is a bug.");
-		}
-#else
-		maybe_cleanup();
-#endif
-	}
-};
-
-#endif
-
 #endif // SAFE_LIST_H
diff --git a/core/templates/safe_refcount.h b/core/templates/safe_refcount.h
index 1f6551762e..c4ffe5ca02 100644
--- a/core/templates/safe_refcount.h
+++ b/core/templates/safe_refcount.h
@@ -33,8 +33,6 @@
 
 #include "core/typedefs.h"
 
-#if !defined(NO_THREADS)
-
 #include <atomic>
 #include <type_traits>
 
@@ -191,141 +189,4 @@ public:
 	}
 };
 
-#else
-
-template <class T>
-class SafeNumeric {
-protected:
-	T value;
-
-public:
-	_ALWAYS_INLINE_ void set(T p_value) {
-		value = p_value;
-	}
-
-	_ALWAYS_INLINE_ T get() const {
-		return value;
-	}
-
-	_ALWAYS_INLINE_ T increment() {
-		return ++value;
-	}
-
-	_ALWAYS_INLINE_ T postincrement() {
-		return value++;
-	}
-
-	_ALWAYS_INLINE_ T decrement() {
-		return --value;
-	}
-
-	_ALWAYS_INLINE_ T postdecrement() {
-		return value--;
-	}
-
-	_ALWAYS_INLINE_ T add(T p_value) {
-		return value += p_value;
-	}
-
-	_ALWAYS_INLINE_ T postadd(T p_value) {
-		T old = value;
-		value += p_value;
-		return old;
-	}
-
-	_ALWAYS_INLINE_ T sub(T p_value) {
-		return value -= p_value;
-	}
-
-	_ALWAYS_INLINE_ T postsub(T p_value) {
-		T old = value;
-		value -= p_value;
-		return old;
-	}
-
-	_ALWAYS_INLINE_ T exchange_if_greater(T p_value) {
-		if (value < p_value) {
-			value = p_value;
-		}
-		return value;
-	}
-
-	_ALWAYS_INLINE_ T conditional_increment() {
-		if (value == 0) {
-			return 0;
-		} else {
-			return ++value;
-		}
-	}
-
-	_ALWAYS_INLINE_ explicit SafeNumeric<T>(T p_value = static_cast<T>(0)) :
-			value(p_value) {
-	}
-};
-
-class SafeFlag {
-protected:
-	bool flag;
-
-public:
-	_ALWAYS_INLINE_ bool is_set() const {
-		return flag;
-	}
-
-	_ALWAYS_INLINE_ void set() {
-		flag = true;
-	}
-
-	_ALWAYS_INLINE_ void clear() {
-		flag = false;
-	}
-
-	_ALWAYS_INLINE_ void set_to(bool p_value) {
-		flag = p_value;
-	}
-
-	_ALWAYS_INLINE_ explicit SafeFlag(bool p_value = false) :
-			flag(p_value) {}
-};
-
-class SafeRefCount {
-	uint32_t count = 0;
-
-public:
-	_ALWAYS_INLINE_ bool ref() { // true on success
-		if (count != 0) {
-			++count;
-			return true;
-		} else {
-			return false;
-		}
-	}
-
-	_ALWAYS_INLINE_ uint32_t refval() { // none-zero on success
-		if (count != 0) {
-			return ++count;
-		} else {
-			return 0;
-		}
-	}
-
-	_ALWAYS_INLINE_ bool unref() { // true if must be disposed of
-		return --count == 0;
-	}
-
-	_ALWAYS_INLINE_ uint32_t unrefval() { // 0 if must be disposed of
-		return --count;
-	}
-
-	_ALWAYS_INLINE_ uint32_t get() const {
-		return count;
-	}
-
-	_ALWAYS_INLINE_ void init(uint32_t p_value = 1) {
-		count = p_value;
-	}
-};
-
-#endif
-
 #endif // SAFE_REFCOUNT_H