Re: [Qemu-devel] [PATCHv4 1/4] util: introduce MIN_NON_ZERO

[Max Reitz <mreitz@redhat.com>]

On 2014-10-16 at 09:54, 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 |    4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 1565404..9a238df 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -68,6 +68,10 @@ typedef signed int              int_fast16_t;
>   #define MAX(a, b) (((a) > (b)) ? (a) : (b))
>   #endif
>   
> +#ifndef MIN_NON_ZERO
> +#define MIN_NON_ZERO(a, b) ((!!(a) && (a) < (b)) ? (a) : (b))

I contrast to Eric I'd even like (a) != 0 instead of !!(a). I normally 
use just "foo" instead of "foo != 0" or "foo != NULL", but in this case 
I'd like (a) != 0 (or (a) > 0) because of the name "NON_ZERO".

Now you have three alternatives to choose from. You're welcome. :-)

Anyway, I'm fine with any, so:

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

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