cut: improve detection of invalid ranges

Commit 0068ce2fa (cut: add toybox-compatible options -O OUTSEP,
-D, -F LIST) added detection of reversed ranges.  Further
improvements are possible.

- The test for reversed ranges compared the start after it had been
  decremented with the end before decrement.  It thus missed ranges
  of the form 2-1.

- Zero isn't a valid start value for a range.  (Nor is it a valid
  end value, but that's caught by the test for a reversed range.)

- The code

        if (!*ltok)
            e = INT_MAX;

  duplicates a check that's already been made.

- Display the actual range in the error message to make it easier
  to find which range was at fault.

function                                             old     new   delta
.rodata                                           100273  100287     +14
cut_main                                            1239    1237      -2
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/1 up/down: 14/-2)              Total: 12 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 12 insertions, 12 deletions

diff --git a/coreutils/cut.c b/coreutils/cut.c
index b7fe11126..f68bbbad5 100644
--- a/coreutils/cut.c
+++ b/coreutils/cut.c
@@ -278,29 +278,26 @@ int cut_main(int argc UNUSED_PARAM, char **argv)
                         if (!ntok[0]) {
                                 s = 0;
                         } else {
-                                s = xatoi_positive(ntok);
                                 /* account for the fact that arrays are zero based, while
                                  * the user expects the first char on the line to be char #1 */
-                                if (s != 0)
-                                        s--;
+                                s = xatoi_positive(ntok) - 1;
                         }
 
                         /* get the end pos */
                         if (ltok == NULL) {
                                 e = s;
                         } else if (!ltok[0]) {
+                                /* if the user specified no end position,
+                                 * that means "til the end of the line" */
                                 e = INT_MAX;
                         } else {
-                                e = xatoi_positive(ltok);
-                                /* if the user specified and end position of 0,
-                                 * that means "til the end of the line" */
-                                if (!*ltok)
-                                        e = INT_MAX;
-                                else if (e < s)
-                                        bb_error_msg_and_die("%d<%d", e, s);
-                                e--;    /* again, arrays are zero based, lines are 1 based */
+                                /* again, arrays are zero based, lines are 1 based */
+                                e = xatoi_positive(ltok) - 1;
                         }
 
+                        if (s < 0 || e < s)
+                                bb_error_msg_and_die("invalid range %s-%s", ntok, ltok ?: ntok);
+
                         /* add the new list */
                         cut_lists = xrealloc_vector(cut_lists, 4, nlists);
                         /* NB: startpos is always >= 0 */
diff --git a/testsuite/cut.tests b/testsuite/cut.tests
index 0b401bc00..c335f824b 100755
--- a/testsuite/cut.tests
+++ b/testsuite/cut.tests
@@ -31,7 +31,10 @@ testing "-b encapsulated" "cut -b 3-8,4-6 input" "e:two:\npha:be\ne quic\n" \
 #testing "cut -bO overlaps" \
 #  "cut --output-delimiter ' ' -b 1-3,2-5,7-9,9-10 input" \
 #  "one:t o:th\nalpha beta\nthe q ick \n" "$abc" ""
-testing "cut high-low error" "cut -b 8-3 abc.txt 2>/dev/null || echo err" "err\n" \
+testing "cut high-low error" "cut -b 8-3 input 2>/dev/null || echo err" "err\n" \
+  "$abc" ""
+
+testing "cut -b 2-1 error" "cut -b 2-1 input 2>/dev/null || echo err" "err\n" \
   "$abc" ""
 
 testing "cut -c a-b" "cut -c 4-10 input" ":two:th\nha:beta\n quick \n" "$abc" ""