netdev - Re: [PATCH v2] selftests/bpf: Fix unsigned expression compared with zero

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Message-ID: <e03209cb-00c7-e282-c2a6-9a2bab0b147f@infradead.org>
Date:   Sat, 5 Nov 2022 09:16:31 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Kang Minchul <tegongkang@...il.com>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>
Cc:     Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] selftests/bpf: Fix unsigned expression compared with
 zero

Hi--

On 11/5/22 03:25, Kang Minchul wrote:
> Variable ret is compared with zero even though it was set as u32.

It's OK to compare a u32 == to zero, but 'ret' is compared to < 0,
which it cannot be. Better explanation here would be good.
Thanks.

> So u32 to int conversion is needed.
> 
> Signed-off-by: Kang Minchul <tegongkang@...il.com>
> ---
>  tools/testing/selftests/bpf/xskxceiver.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/xskxceiver.c b/tools/testing/selftests/bpf/xskxceiver.c
> index 681a5db80dae..162d3a516f2c 100644
> --- a/tools/testing/selftests/bpf/xskxceiver.c
> +++ b/tools/testing/selftests/bpf/xskxceiver.c
> @@ -1006,7 +1006,8 @@ static int __send_pkts(struct ifobject *ifobject, u32 *pkt_nb, struct pollfd *fd
>  {
>  	struct xsk_socket_info *xsk = ifobject->xsk;
>  	bool use_poll = ifobject->use_poll;
> -	u32 i, idx = 0, ret, valid_pkts = 0;
> +	u32 i, idx = 0, valid_pkts = 0;
> +	int ret;
>  
>  	while (xsk_ring_prod__reserve(&xsk->tx, BATCH_SIZE, &idx) < BATCH_SIZE) {
>  		if (use_poll) {

-- 
~Randy