Fix some IPC issues

Socket now includes pid in the filename (fixes nested sway sessions or
old sockets causing problems).

Fixed warnings on strict aliasing and cleaned up relevant code in
general.

sway/ipc.c

@@ -98,7 +98,8 @@ struct sockaddr_un *ipc_user_sockaddr(void) {
 	int path_size = sizeof(ipc_sockaddr->sun_path);
 
 	// Without logind:
-	int allocating_path_size = snprintf(ipc_sockaddr->sun_path, path_size, "/tmp/sway-ipc.%i.sock", getuid());
+	int allocating_path_size = snprintf(ipc_sockaddr->sun_path, path_size,
+			"/tmp/sway-ipc.%i.%i.sock", getuid(), getpid());
 
 	if (allocating_path_size >= path_size) {
 		sway_abort("socket path won't fit into ipc_sockaddr->sun_path");
@@ -176,7 +177,8 @@ int ipc_client_handle_readable(int client_fd, uint32_t mask, void *data) {
 		return 0;
 	}
 
-	char buf[ipc_header_size];
+	uint8_t buf[ipc_header_size];
+	uint32_t *buf32 = (uint32_t*)(buf + sizeof(ipc_magic));
 	ssize_t received = recv(client_fd, buf, ipc_header_size, 0);
 	if (received == -1) {
 		sway_log_errno(L_INFO, "Unable to receive header from IPC client");
@@ -190,8 +192,8 @@ int ipc_client_handle_readable(int client_fd, uint32_t mask, void *data) {
 		return 0;
 	}
 
-	client->payload_length = *(uint32_t *)&buf[sizeof(ipc_magic)];
-	client->current_command = (enum ipc_command_type) *(uint32_t *)&buf[sizeof(ipc_magic)+4];
+	client->payload_length = buf32[0];
+	client->current_command = (enum ipc_command_type)buf32[1];
 
 	if (read_available - received >= client->payload_length) {
 		ipc_client_handle_command(client);
@@ -336,10 +338,11 @@ bool ipc_send_reply(struct ipc_client *client, const char *payload, uint32_t pay
 	assert(payload);
 
 	char data[ipc_header_size];
+	uint32_t *data32 = (uint32_t*)(data + sizeof(ipc_magic));
 
 	memcpy(data, ipc_magic, sizeof(ipc_magic));
-	*(uint32_t *)&(data[sizeof(ipc_magic)]) = payload_length;
-	*(uint32_t *)&(data[sizeof(ipc_magic)+4]) = client->current_command;
+	data32[0] = payload_length;
+	data32[1] = client->current_command;
 
 	if (write(client->fd, data, ipc_header_size) == -1) {
 		sway_log_errno(L_INFO, "Unable to send header to IPC client");