On Wednesday 05 July 2006 20:49, Eric Sesterhenn / Snakebyte wrote:
> * Dmitry Torokhov ([email protected]) wrote:
> > On 7/5/06, Henk Vergonet <[email protected]> wrote:
> > >On Tue, Jun 27, 2006 at 03:51:43PM -0700, Randy.Dunlap wrote:
> > >> On Wed, 28 Jun 2006 00:41:19 +0200 Eric Sesterhenn wrote:
> > >> > another off by one spotted by coverity (id #485),
> > >> > we loop exactly one time too often
> > >> >
> > >> > Signed-off-by: Eric Sesterhenn <[email protected]>
> > >> >
> > >> > --- linux-2.6.17-git11/drivers/usb/input/yealink.c.orig 2006-06-28
> > >00:29:46.000000000 +0200
> > >> > +++ linux-2.6.17-git11/drivers/usb/input/yealink.c 2006-06-28
> > >00:30:04.000000000 +0200
> > >> > @@ -350,7 +350,7 @@ static int yealink_do_idle_tasks(struct
> > >> > val = yld->master.b[ix];
> > >> > if (val != yld->copy.b[ix])
> > >> > goto send_update;
> > >> > - } while (++ix < sizeof(yld->master));
> > >> > + } while (++ix < sizeof(yld->master)-1);
> > >
> > >Apart from introducing a new bug in the code, the construct is ugly.
> > >
> > >I would rather see then the more readable:
> > >
> > > ix++;
> > > } while (ix < sizeof(yld->master));
> > >
> >
> > The new code is exactly the same as the old one; however I do not see
> > the problem with the old code. Could it be that Coverity got confused
> > by prefix vs. postfix increment?
>
> I looked at this code several times too, and tried to reproduce the bug
> with the following little program:
>
> #include <string.h>
> int main(int argc, char **argv) {
> char foo[] = "abcdef";
> int i = 0;
>
> foo[strlen(foo)] = 'X';
> do {
> putchar(foo[i]);
> } while (++i < sizeof(foo));
> }
>
> Which clearly shows that the terminating '\0' gets printed too,
> replaced by the X for better visibility, so the code
> runs past the array, or did I fail to replicate the original
> code somewhere?
>
What do you mean "the code runs past the array"? The size of array is 7
(compiler allocates the space for terminating '\0') and the array is
printed in its entirety.
--
Dmitry
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