ipc: fix aligment issue of data buffer

The pointer `data` is cast to a more strictly aligned pointer type. To
prevent issues, the `data32` buffer is removed and its occurrences are
replaced with an offset from the `data` buffer.

common/ipc-client.c

@@ -79,7 +79,6 @@ bool ipc_set_recv_timeout(int socketfd, struct timeval tv) {
 
 struct ipc_response *ipc_recv_response(int socketfd) {
 	char data[IPC_HEADER_SIZE];
-	uint32_t *data32 = (uint32_t *)(data + sizeof(ipc_magic));
 
 	size_t total = 0;
 	while (total < IPC_HEADER_SIZE) {
@@ -95,15 +94,15 @@ struct ipc_response *ipc_recv_response(int socketfd) {
 		goto error_1;
 	}
 
-	total = 0;
-	memcpy(&response->size, &data32[0], sizeof(data32[0]));
-	memcpy(&response->type, &data32[1], sizeof(data32[1]));
+	memcpy(&response->size, data + sizeof(ipc_magic), sizeof(uint32_t));
+	memcpy(&response->type, data + sizeof(ipc_magic) + sizeof(uint32_t), sizeof(uint32_t));
 
 	char *payload = malloc(response->size + 1);
 	if (!payload) {
 		goto error_2;
 	}
 
+	total = 0;
 	while (total < response->size) {
 		ssize_t received = recv(socketfd, payload + total, response->size - total, 0);
 		if (received < 0) {
@@ -129,10 +128,9 @@ void free_ipc_response(struct ipc_response *response) {
 
 char *ipc_single_command(int socketfd, uint32_t type, const char *payload, uint32_t *len) {
 	char data[IPC_HEADER_SIZE];
-	uint32_t *data32 = (uint32_t *)(data + sizeof(ipc_magic));
 	memcpy(data, ipc_magic, sizeof(ipc_magic));
-	memcpy(&data32[0], len, sizeof(*len));
-	memcpy(&data32[1], &type, sizeof(type));
+	memcpy(data + sizeof(ipc_magic), len, sizeof(*len));
+	memcpy(data + sizeof(ipc_magic) + sizeof(*len), &type, sizeof(type));
 
 	if (write(socketfd, data, IPC_HEADER_SIZE) == -1) {
 		sway_abort("Unable to send IPC header");

sway/ipc-server.c

@@ -242,7 +242,6 @@ int ipc_client_handle_readable(int client_fd, uint32_t mask, void *data) {
 	}
 
 	uint8_t buf[IPC_HEADER_SIZE];
-	uint32_t *buf32 = (uint32_t*)(buf + sizeof(ipc_magic));
 	// Should be fully available, because read_available >= IPC_HEADER_SIZE
 	ssize_t received = recv(client_fd, buf, IPC_HEADER_SIZE, 0);
 	if (received == -1) {
@@ -257,8 +256,8 @@ int ipc_client_handle_readable(int client_fd, uint32_t mask, void *data) {
 		return 0;
 	}
 
-	memcpy(&client->pending_length, &buf32[0], sizeof(buf32[0]));
-	memcpy(&client->pending_type, &buf32[1], sizeof(buf32[1]));
+	memcpy(&client->pending_length, buf + sizeof(ipc_magic), sizeof(uint32_t));
+	memcpy(&client->pending_type, buf + sizeof(ipc_magic) + sizeof(uint32_t), sizeof(uint32_t));
 
 	if (read_available - received >= (long)client->pending_length) {
 		// Reset pending values.
@@ -920,11 +919,10 @@ bool ipc_send_reply(struct ipc_client *client, enum ipc_command_type payload_typ
 	assert(payload);
 
 	char data[IPC_HEADER_SIZE];
-	uint32_t *data32 = (uint32_t*)(data + sizeof(ipc_magic));
 
 	memcpy(data, ipc_magic, sizeof(ipc_magic));
-	memcpy(&data32[0], &payload_length, sizeof(payload_length));
-	memcpy(&data32[1], &payload_type, sizeof(payload_type));
+	memcpy(data + sizeof(ipc_magic), &payload_length, sizeof(payload_length));
+	memcpy(data + sizeof(ipc_magic) + sizeof(payload_length), &payload_type, sizeof(payload_type));
 
 	while (client->write_buffer_len + IPC_HEADER_SIZE + payload_length >=
 				 client->write_buffer_size) {