Add rename cache for thread safety

This just ensures that if an obs object is renamed that the pointer to
older names will still be valid.  Prevents renames from causing any
invalid memory access.

When the obs object is destroyed, so are the cached names.

libobs/obs-internal.h

@@ -198,6 +198,9 @@ struct obs_context_data {
 	signal_handler_t                signals;
 	proc_handler_t                  procs;
 
+	DARRAY(char*)                   rename_cache;
+	pthread_mutex_t                 rename_cache_mutex;
+
 	pthread_mutex_t                 *mutex;
 	struct obs_context_data         *next;
 	struct obs_context_data         **prev_next;

libobs/obs.c

@@ -1189,8 +1189,12 @@ static inline bool obs_context_data_init_wrap(
 {
 	assert(context);
 
+	pthread_mutex_init_value(&context->rename_cache_mutex);
 	obs_context_data_free(context);
 
+	if (pthread_mutex_init(&context->rename_cache_mutex, NULL) < 0)
+		return false;
+
 	context->signals = signal_handler_create();
 	if (!context)
 		return false;
@@ -1201,6 +1205,8 @@ static inline bool obs_context_data_init_wrap(
 
 	context->name     = dup_name(name);
 	context->settings = obs_data_newref(settings);
+
+	da_init(context->rename_cache);
 	return true;
 }
 
@@ -1223,8 +1229,13 @@ void obs_context_data_free(struct obs_context_data *context)
 	proc_handler_destroy(context->procs);
 	obs_data_release(context->settings);
 	obs_context_data_remove(context);
+	pthread_mutex_destroy(&context->rename_cache_mutex);
 	bfree(context->name);
 
+	for (size_t i = 0; i < context->rename_cache.num; i++)
+		bfree(context->rename_cache.array[i]);
+	da_free(context->rename_cache);
+
 	memset(context, 0, sizeof(*context));
 }
 
@@ -1264,6 +1275,11 @@ void obs_context_data_remove(struct obs_context_data *context)
 void obs_context_data_setname(struct obs_context_data *context,
 		const char *name)
 {
-	bfree(context->name);
+	pthread_mutex_lock(&context->rename_cache_mutex);
+
+	if (context->name)
+		da_push_back(context->rename_cache, &context->name);
 	context->name = dup_name(name);
+
+	pthread_mutex_unlock(&context->rename_cache_mutex);
 }