[Bug 191719] New: bin/expr doesn't detect some overflow errors with multiplication

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=191719

            Bug ID: 191719
           Summary: bin/expr doesn't detect some overflow errors with
                    multiplication
           Product: Base System
           Version: 11.0-CURRENT
          Hardware: Any
                OS: Any
            Status: Needs Triage
          Severity: Affects Some People
          Priority: ---
         Component: bin
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: yaneurabeya at gmail.com

If I do the following case, it doesn't fail on FreeBSD like it does NetBSD:

% expr -- -4611686018427387904 \* 3
4611686018427387904
# python2 -c 'print -4611686018427387904 * 3'
-13835058055282163712

This is could be fixed by adding a signage check to assert_times, like what's
in assert_plus: if the signage of two numbers is not the same, i.e. one is
negative, the other is positive -- then the value must be negative.

395 void
396 assert_plus(intmax_t a, intmax_t b, intmax_t r)
397 {
398         /*
399          * sum of two positive numbers must be positive,
400          * sum of two negative numbers must be negative
401          */
402         if ((a > 0 && b > 0 && r <= 0) ||
403             (a < 0 && b < 0 && r >= 0))
404                 errx(ERR_EXIT, "overflow");
405 }
...
447 void
448 assert_times(intmax_t a, intmax_t b, intmax_t r)
449 {
450         /*
451          * if first operand is 0, no overflow is possible,
452          * else result of division test must match second operand
453          */
454         if (a != 0 && r / a != b)
455                 errx(ERR_EXIT, "overflow");
456 }

-- 
You are receiving this mail because:
You are the assignee for the bug.