spci: Terminate all commands with a linefeed for all transports

While some transports add a terminating (carriagereturn+)linefeed
unconditionally, the USBTMC transport does not. At least the R&S HMO1002
requires the linefeed and locks up otherwise. Fixes bug #784.

This changes the TCP and VXI transport from CR+LF to LF only.

Also fixes a possible memory leak for VXI, where the temporary command
buffer was not freed in case of a write error.

src/scpi/scpi.c

@@ -296,8 +296,10 @@ SR_PRIV int sr_scpi_send_variadic(struct sr_scpi_dev_inst *scpi,
 	va_end(args_copy);
 
 	/* Allocate buffer and write out command. */
-	buf = g_malloc(len + 1);
+	buf = g_malloc0(len + 2);
 	vsprintf(buf, format, args);
+	if (buf[len - 1] != '\n')
+		buf[len] = '\n';
 
 	/* Send command. */
 	ret = scpi->send(scpi->priv, buf);

src/scpi/scpi_serial.c

@@ -123,26 +123,21 @@ static int scpi_serial_source_remove(struct sr_session *session, void *priv)
 static int scpi_serial_send(void *priv, const char *command)
 {
 	int len, result, written;
-	gchar *terminated_command;
 	struct scpi_serial *sscpi = priv;
 	struct sr_serial_dev_inst *serial = sscpi->serial;
 
-	terminated_command = g_strconcat(command, "\n", NULL);
-	len = strlen(terminated_command);
+	len = strlen(command);
 	written = 0;
 	while (written < len) {
 		result = serial_write_nonblocking(serial,
-				terminated_command + written, len - written);
+				command + written, len - written);
 		if (result < 0) {
 			sr_err("Error while sending SCPI command: '%s'.", command);
-			g_free(terminated_command);
 			return SR_ERR;
 		}
 		written += result;
 	}
 
-	g_free(terminated_command);
-
 	sr_spew("Successfully sent SCPI command: '%s'.", command);
 
 	return SR_OK;

src/scpi/scpi_tcp.c

@@ -135,12 +135,9 @@ static int scpi_tcp_send(void *priv, const char *command)
 {
 	struct scpi_tcp *tcp = priv;
 	int len, out;
-	char *terminated_command;
 
-	terminated_command = g_strdup_printf("%s\r\n", command);
-	len = strlen(terminated_command);
-	out = send(tcp->socket, terminated_command, len, 0);
-	g_free(terminated_command);
+	len = strlen(command);
+	out = send(tcp->socket, command, len, 0);
 
 	if (out < 0) {
 		sr_err("Send error: %s", g_strerror(errno));

src/scpi/scpi_visa.c

@@ -87,21 +87,16 @@ static int scpi_visa_source_remove(struct sr_session *session, void *priv)
 static int scpi_visa_send(void *priv, const char *command)
 {
 	struct scpi_visa *vscpi = priv;
-	gchar *terminated_command;
 	ViUInt32 written = 0;
 	int len;
 
-	terminated_command = g_strconcat(command, "\n", NULL);
-	len = strlen(terminated_command);
-	if (viWrite(vscpi->vi, (ViBuf) (terminated_command + written), len,
+	len = strlen(command);
+	if (viWrite(vscpi->vi, (ViBuf) (command + written), len,
 			&written) != VI_SUCCESS) {
 		sr_err("Error while sending SCPI command: '%s'.", command);
-		g_free(terminated_command);
 		return SR_ERR;
 	}
 
-	g_free(terminated_command);
-
 	sr_spew("Successfully sent SCPI command: '%s'.", command);
 
 	return SR_OK;

src/scpi/scpi_vxi.c

@@ -118,18 +118,16 @@ static int scpi_vxi_send(void *priv, const char *command)
 	struct scpi_vxi *vxi = priv;
 	Device_WriteResp *write_resp;
 	Device_WriteParms write_parms;
-	char *terminated_command;
 	unsigned long len;
 
-	terminated_command = g_strdup_printf("%s\r\n", command);
-	len = strlen(terminated_command);
+	len = strlen(command);
 
 	write_parms.lid           = vxi->link;
 	write_parms.io_timeout    = VXI_DEFAULT_TIMEOUT_MS;
 	write_parms.lock_timeout  = VXI_DEFAULT_TIMEOUT_MS;
 	write_parms.flags         = DF_END;
 	write_parms.data.data_len = MIN(len, vxi->max_send_size);
-	write_parms.data.data_val = terminated_command;
+	write_parms.data.data_val = command;
 
 	if (!(write_resp = device_write_1(&write_parms, vxi->client))
 	    || write_resp->error) {
@@ -138,8 +136,6 @@ static int scpi_vxi_send(void *priv, const char *command)
 		return SR_ERR;
 	}
 
-	g_free(terminated_command);
-
 	if (write_resp->size < len)
 		sr_dbg("Only sent %lu/%lu bytes of SCPI command: '%s'.",
 		       write_resp->size, len, command);