Fix potential misuse of unions

Issue: #478
Reported by: @moisseev

src/fuzzy_storage.c

@@ -149,6 +149,7 @@ struct fuzzy_session {
 };
 
 struct fuzzy_peer_cmd {
+	gboolean is_shingle;
 	union {
 		struct rspamd_fuzzy_cmd normal;
 		struct rspamd_fuzzy_shingle_cmd shingle;
@@ -210,19 +211,30 @@ static void
 rspamd_fuzzy_process_updates_queue (struct rspamd_fuzzy_storage_ctx *ctx)
 {
 	GList *cur;
-	struct fuzzy_peer_cmd *cmd;
+	struct fuzzy_peer_cmd *io_cmd;
+	struct rspamd_fuzzy_cmd *cmd;
+	gpointer ptr;
 	guint nupdates = 0;
 
 	if (rspamd_fuzzy_backend_prepare_update (ctx->backend)) {
 		cur = ctx->updates_pending->head;
 		while (cur) {
-			cmd = cur->data;
+			io_cmd = cur->data;
+
+			if (io_cmd->is_shingle) {
+				cmd = &io_cmd->cmd.shingle.basic;
+				ptr = &io_cmd->cmd.shingle;
+			}
+			else {
+				cmd = &io_cmd->cmd.normal;
+				ptr = &io_cmd->cmd.normal;
+			}
 
-			if (cmd->cmd.normal.cmd == FUZZY_WRITE) {
-				rspamd_fuzzy_backend_add (ctx->backend, &cmd->cmd.normal);
+			if (cmd->cmd == FUZZY_WRITE) {
+				rspamd_fuzzy_backend_add (ctx->backend, ptr);
 			}
 			else {
-				rspamd_fuzzy_backend_del (ctx->backend, &cmd->cmd.normal);
+				rspamd_fuzzy_backend_del (ctx->backend, ptr);
 			}
 
 			nupdates++;
@@ -234,8 +246,8 @@ rspamd_fuzzy_process_updates_queue (struct rspamd_fuzzy_storage_ctx *ctx)
 			cur = ctx->updates_pending->head;
 
 			while (cur) {
-				cmd = cur->data;
-				g_slice_free1 (sizeof (*cmd), cmd);
+				io_cmd = cur->data;
+				g_slice_free1 (sizeof (*io_cmd), io_cmd);
 				cur = g_list_next (cur);
 			}
 
@@ -387,6 +399,7 @@ rspamd_fuzzy_process_command (struct fuzzy_session *session)
 	struct fuzzy_peer_request *up_req;
 	struct fuzzy_key_stat *ip_stat = NULL;
 	rspamd_inet_addr_t *naddr;
+	gpointer ptr;
 	gsize up_len;
 
 	switch (session->cmd_type) {
@@ -441,14 +454,22 @@ rspamd_fuzzy_process_command (struct fuzzy_session *session)
 
 			if (session->worker->index == 0 || session->ctx->peer_fd == -1) {
 				/* Just add to the queue */
-				up_cmd = g_slice_alloc (sizeof (*up_cmd));
-				memcpy (up_cmd, cmd, up_len);
+				up_cmd = g_slice_alloc0 (sizeof (*up_cmd));
+				up_cmd->is_shingle = is_shingle;
+				ptr = is_shingle ?
+						(gpointer)&up_cmd->cmd.shingle :
+						(gpointer)&up_cmd->cmd.normal;
+				memcpy (ptr, cmd, up_len);
 				g_queue_push_tail (session->ctx->updates_pending, up_cmd);
 			}
 			else {
 				/* We need to send request to the peer */
-				up_req = g_slice_alloc (sizeof (*up_req));
-				memcpy (&up_req->cmd, cmd, up_len);
+				up_req = g_slice_alloc0 (sizeof (*up_req));
+				up_req->cmd.is_shingle = is_shingle;
+				ptr = is_shingle ?
+						(gpointer)&up_req->cmd.cmd.shingle :
+						(gpointer)&up_req->cmd.cmd.normal;
+				memcpy (ptr, cmd, up_len);
 				event_set (&up_req->io_ev, session->ctx->peer_fd, EV_WRITE,
 						fuzzy_peer_send_io, up_req);
 				event_base_set (session->ctx->ev_base, &up_req->io_ev);