Improve custom thread numbering for POSIX

We lazily assign new IDs to threads that do not have one. This is the case for threads not created by the Godot API.

drivers/unix/thread_posix.cpp

@@ -40,9 +40,13 @@
 #include "core/os/memory.h"
 #include "core/safe_refcount.h"
 
+static void _thread_id_key_destr_callback(void *p_value) {
+	memdelete(static_cast<Thread::ID *>(p_value));
+}
+
 static pthread_key_t _create_thread_id_key() {
 	pthread_key_t key;
-	pthread_key_create(&key, NULL);
+	pthread_key_create(&key, &_thread_id_key_destr_callback);
 	return key;
 }
 
@@ -63,7 +67,7 @@ void *ThreadPosix::thread_callback(void *userdata) {
 
 	ThreadPosix *t = reinterpret_cast<ThreadPosix *>(userdata);
 	t->id = atomic_increment(&next_thread_id);
-	pthread_setspecific(thread_id_key, (void *)t->id);
+	pthread_setspecific(thread_id_key, (void *)memnew(ID(t->id)));
 
 	ScriptServer::thread_enter(); //scripts may need to attach a stack
 
@@ -89,7 +93,14 @@ Thread *ThreadPosix::create_func_posix(ThreadCreateCallback p_callback, void *p_
 }
 Thread::ID ThreadPosix::get_thread_id_func_posix() {
 
-	return (ID)pthread_getspecific(thread_id_key);
+	void *value = pthread_getspecific(thread_id_key);
+
+	if (value)
+		return *static_cast<ID *>(value);
+
+	ID new_id = atomic_increment(&next_thread_id);
+	pthread_setspecific(thread_id_key, (void *)memnew(ID(new_id)));
+	return new_id;
 }
 void ThreadPosix::wait_to_finish_func_posix(Thread *p_thread) {
 

platform/android/thread_jandroid.cpp

@@ -34,9 +34,13 @@
 #include "core/safe_refcount.h"
 #include "core/script_language.h"
 
+static void _thread_id_key_destr_callback(void *p_value) {
+	memdelete(static_cast<Thread::ID *>(p_value));
+}
+
 static pthread_key_t _create_thread_id_key() {
 	pthread_key_t key;
-	pthread_key_create(&key, NULL);
+	pthread_key_create(&key, &_thread_id_key_destr_callback);
 	return key;
 }
 
@@ -59,7 +63,7 @@ void *ThreadAndroid::thread_callback(void *userdata) {
 	setup_thread();
 	ScriptServer::thread_enter(); //scripts may need to attach a stack
 	t->id = atomic_increment(&next_thread_id);
-	pthread_setspecific(thread_id_key, (void *)t->id);
+	pthread_setspecific(thread_id_key, (void *)memnew(ID(t->id)));
 	t->callback(t->user);
 	ScriptServer::thread_exit();
 	return NULL;
@@ -80,7 +84,14 @@ Thread *ThreadAndroid::create_func_jandroid(ThreadCreateCallback p_callback, voi
 
 Thread::ID ThreadAndroid::get_thread_id_func_jandroid() {
 
-	return (ID)pthread_getspecific(thread_id_key);
+	void *value = pthread_getspecific(thread_id_key);
+
+	if (value)
+		return *static_cast<ID *>(value);
+
+	ID new_id = atomic_increment(&next_thread_id);
+	pthread_setspecific(thread_id_key, (void *)memnew(ID(new_id)));
+	return new_id;
 }
 
 void ThreadAndroid::wait_to_finish_func_jandroid(Thread *p_thread) {