[ovs-dev] [patch_v1] ovs build: Fix memset with zero size warning.

[Eric Garver]

On Sun, Mar 19, 2017 at 10:11:09AM -0700, Darrell Ball wrote:
> In file included from /usr/include/string.h:640:0,
>                  from ./lib/string.h:20,
>                  from /usr/include/netinet/icmp6.h:22,
>                  from ../lib/flow.h:21,
>                  from ../lib/flow.c:18:
> In function 'memset',
>     inlined from 'flow_push_vlan_uninit' at ../lib/flow.c:2188:19:
> /usr/include/x86_64-linux-gnu/bits/string3.h:81:30: error:
> call to '__warn_memset_zero_len' declared with attribute warning:
> memset used with constant zero length parameter; this could be
> due to transposed parameters [-Werror]
>        __warn_memset_zero_len ();
>                               ^
> cc1: all warnings being treated as errors
> make[2]: *** [lib/flow.lo] Error 1
> 
> Fixes: f0fb825a3785 ("Add support for 802.1ad (QinQ tunneling)")
> Signed-off-by: Darrell Ball <dlu998 at gmail.com>
> ---
>  lib/flow.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/flow.c b/lib/flow.c
> index f628526..0a67455 100644
> --- a/lib/flow.c
> +++ b/lib/flow.c
> @@ -2184,7 +2184,9 @@ flow_push_vlan_uninit(struct flow *flow, struct flow_wildcards *wc)
>  {
>      if (wc) {
>          int n = flow_count_vlan_headers(flow);
> -        memset(wc->masks.vlans, 0xff, sizeof(union flow_vlan_hdr) * n);
> +        if (n) {

Better to use (n > 0) since n is of type int.

Thanks!

> +            memset(wc->masks.vlans, 0xff, sizeof(union flow_vlan_hdr) * n);
> +        }
>      }
>      memmove(&flow->vlans[1], &flow->vlans[0],
>              sizeof(union flow_vlan_hdr) * (FLOW_MAX_VLAN_HEADERS - 1));
> -- 
> 1.9.1