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    SubjectRe: [PATCH 4.19 28/37] dmaengine: dmatest: Fix iteration non-stop logic
    On Tue 2020-05-05 11:32:27, Sasha Levin wrote:
    > On Tue, May 05, 2020 at 05:05:37PM +0300, Andy Shevchenko wrote:
    > > On Tue, May 5, 2020 at 4:37 PM Pavel Machek <pavel@denx.de> wrote:
    > > > On Tue 2020-05-05 16:19:11, Andy Shevchenko wrote:
    > > > > On Tue, May 5, 2020 at 3:58 PM Pavel Machek <pavel@denx.de> wrote:
    > > > > > On Tue 2020-05-05 15:51:16, Andy Shevchenko wrote:
    > > > > > > On Tue, May 5, 2020 at 3:37 PM Pavel Machek <pavel@denx.de> wrote:
    > > > > > Yeah, I pointed that out above. Both && and || permit short
    > > > > > execution. But that does not matter, as neither "params->iterations"
    > > > > > nor "total_tests >= params->iterations" have side effects.
    > > > > >
    > > > > > Where is the runtime difference?
    > > > >
    > > > > We have to check *both* conditions. If we don't check iterations, we
    > > > > just wait indefinitely until somebody tells us to stop.
    > > > > Everything in the commit message and mentioned there commit IDs which
    > > > > you may check.
    > > >
    > > > No.
    > >
    > > Yes. Please, read carefully the commit message (for your convenience I
    > > emphasized above). I don't want to spend time on this basics stuff
    > > anymore.
    >
    > I'm a bit confused about this too. Maybe it's too early in the morning,
    > so I wrote this little test program:
    >
    > #include <stdio.h>
    > #include <stdlib.h>
    >
    > int main(int argc, char *argv[])
    > {
    > int a = atoi(argv[1]);
    > int b = atoi(argv[2]);
    >
    > if (!a && !b)
    > printf("A");
    > else
    > printf("B");
    >
    > if (!(a || b))
    > printf("A");
    > else
    > printf("B");
    >
    > printf("\n");
    >
    > return 0;
    > }
    >
    > Andy, could you give an example of two values which will print something
    > other than "AA" or "BB"?

    The issue here is "sideffects". Does b have to be evaluated at all?
    There is no difference between

    int a, b;
    if (a && b)

    and

    if ((!!a) & (!!b))
    .

    But there would be difference between

    int a, b;
    if (a && b++)

    and
    if ((!!a) & (!!(b++)))

    But:

    1) && and || behave same way w.r.t. side effects

    2) in the patch we are talking about b has no important side effects

    Best regards,
    Pavel
    --
    DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
    HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
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