Re: [Qemu-devel] [PATCHv5 1/6] util: introduce MIN_NON_ZERO

[Max Reitz <mreitz@redhat.com>]

On 2014-10-25 at 18:18, Peter Lieven wrote:
> at least in block layer we have the case of limits being defined for a
> BlockDriverState. However, in this context often zero (0) has the special
> meanining of undefined which means no limit. If two of those limits are
> combined and the minimum is needed the minimum function should only return
> zero if both parameters are zero.
>
> Signed-off-by: Peter Lieven <pl@kamp.de>
> ---
>   include/qemu/osdep.h |    6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 1565404..bcdf088 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -68,6 +68,12 @@ typedef signed int              int_fast16_t;
>   #define MAX(a, b) (((a) > (b)) ? (a) : (b))
>   #endif
>   
> +/* Minimum function that returns zero only iff both values are zero.
> + * Intended for use with unsigned values only. */
> +#ifndef MIN_NON_ZERO
> +#define MIN_NON_ZERO(a, b) (((a != 0) && (a) < (b)) ? (a) : (b))

*cough* This should be (((a) != 0 && (a) < (b)) ? (a) : (b)), so the 
parentheses need to enclose the "a", not the "a != 0".

I guess the maintainer could fix that up, though.

And with that fixed, of course,

Reviewed-by: Max Reitz <mreitz@redhat.com>

> +#endif
> +
>   #ifndef ROUND_UP
>   #define ROUND_UP(n,d) (((n) + (d) - 1) & -(d))
>   #endif