[dm-devel] [PATCH 5/6] vector: add lower boundary check in vector_foreach_slot_after

[Martin Wilck]

On Sun, 2020-08-16 at 09:45 +0800, Zhiqiang Liu wrote:
> In vector_foreach_slot_after macro, i is the input var, which
> may have a illegal value (i < 0). So we should add lower boundary
> check in vector_foreach_slot_after macro.
> 
> Signed-off-by: Zhiqiang Liu <liuzhiqiang26 at huawei.com>
> Signed-off-by: lixiaokeng <lixiaokeng at huawei.com>
> ---
>  libmultipath/vector.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)

Perhaps we should write this instead? I'm unsure if compilers can
optimize away the repeated extra check in all cases.

#define vector_foreach_slot_after(v,p,i) \
	if ((v) && (int)(i) >= 0)        \
		for (; (int)(i) < VECTOR_SIZE(v) && ((p) = (v)->slot[i]); (i)++)

Regards,
Martin

> 
> diff --git a/libmultipath/vector.h b/libmultipath/vector.h
> index 2862dc2..45dbfc1 100644
> --- a/libmultipath/vector.h
> +++ b/libmultipath/vector.h
> @@ -38,11 +38,11 @@ typedef struct _vector *vector;
>  #define VECTOR_LAST_SLOT(V)   (((V) && VECTOR_SIZE(V) > 0) ? (V)-
> >slot[(VECTOR_SIZE(V) - 1)] : NULL)
> 
>  #define vector_foreach_slot(v,p,i) \
> -	for (i = 0; (v) && (int)i < VECTOR_SIZE(v) && ((p) = (v)-
> >slot[i]); i++)
> +	for ((i) = 0; (v) && (int)(i) < VECTOR_SIZE(v) && ((p) = (v)-
> >slot[i]); (i)++)
>  #define vector_foreach_slot_after(v,p,i) \
> -	for (; (v) && (int)i < VECTOR_SIZE(v) && ((p) = (v)->slot[i]);
> i++)
> +	for (; (v) && (int)(i) < VECTOR_SIZE(v) && (int)(i) >= 0 &&
> ((p) = (v)->slot[i]); (i)++)
>  #define vector_foreach_slot_backwards(v,p,i) \
> -	for (i = VECTOR_SIZE(v) - 1; (int)i >= 0 && ((p) = (v)-
> >slot[i]); i--)
> +	for ((i) = VECTOR_SIZE(v) - 1; (int)(i) >= 0 && ((p) = (v)-
> >slot[i]); (i)--)
> 
>  #define identity(x) (x)
>  /*