- for (ii = 0; updvals[ds_idx + 1][ii] != '\0'; ii++) {
- if ((updvals[ds_idx + 1][ii] < '0'
- || updvals[ds_idx + 1][ii] > '9')
- && (ii != 0 && updvals[ds_idx + 1][ii] != '-')) {
- rrd_set_error("not a simple integer: '%s'",
- updvals[ds_idx + 1]);
+ /* Check if this is a valid integer. `U' is already handled in
+ * another branch. */
+ for (ii = 0; updvals[ds_idx + 1][ii] != 0; ii++) {
+ if ((ii == 0) && (dst_idx == DST_DERIVE)
+ && (updvals[ds_idx + 1][ii] == '-'))
+ continue;
+
+ if ((updvals[ds_idx + 1][ii] < '0')
+ || (updvals[ds_idx + 1][ii] > '9')) {
+ rrd_set_error("not a simple %s integer: '%s'",
+ (dst_idx == DST_DERIVE) ? "signed" : "unsigned",
+ updvals[ds_idx + 1]);