Coverity check please...

[Gary E. Miller]

Yo Hal!

On Sun, 19 Jan 2025 00:32:01 -0800
Hal Murray via devel <devel at ntpsec.org> wrote:

> I think it's a bug in Coverity.  Would somebody please check.

I agree with coverity.

> Is there a way to report bugs to Coverity?  Or tell it not to check 
> something?

Not that I know of, and we would need a bug first.

> It's getting here with n =2
>  11. known_value_assign: j = n, its value is now 2.
> 471        i = 0; j = n;
> 472        m = n - (n * 4) / 10;
> (n*4)/10 is 0, so m is 2
>       12. Condition j - i > m, taking true branch.
>       16. Condition j - i > m, taking true branch.
>       20. Condition j - i > m, taking true branch.
>      
> CID 497295: (#1 of 1): Overflowed constant (INTEGER_OVERFLOW)
> 24. overflow_const: Expression j - i, where j is known to be equal to
> 2, and i is known to be equal to 3, underflows the type of j - i,
> which is type unsigned long.

Since j is 2, andi is 3, subtracting i from j caused integer wrap, which
is undefined.

> 473        while ((j - i) > m) {

Work with 2s complement, but C does not specify 2s complement.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin