Re: [PATCH 6/9] drivers/net/wireless/iwlwifi/iwl-4965.c: Correct use of ! and &

Christopher Li
2008-03-05T06:50:07Z

I think Al Viro has sent a patch to linux-sparse with subject
"[PATCH 3/3] catch !x & y brainos" does exactly that.

Chris

On Tue, Mar 4, 2008 at 10:38 PM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Julia Lawall <julia@diku.dk> wrote:
>
> > From: Julia Lawall <julia@diku.dk>
> >
> > In commit e6bafba5b4765a5a252f1b8d31cbf6d2459da337, a bug was fixed
> > that involved converting !x & y to !(x & y). The code below shows the
> > same pattern, and thus should perhaps be fixed in the same way.
>
>
> > if (sta_ht_inf) {
> > if ((!sta_ht_inf->ht_supported) ||
> > - (!sta_ht_inf->cap & IEEE80211_HT_CAP_SUP_WIDTH))
> > + (!(sta_ht_inf->cap & IEEE80211_HT_CAP_SUP_WIDTH)))
> > return 0;
>
> i'm wondering, could Sparse be extended to check for such patterns?
>
> People are regularly running "make C=1" and are sending fixes to make
> entire subsystems sparse-warning-free, so Sparse is a nice mechanism
> that works and it keeps code clean in the long run.
>
> I dont think the "!X & Y" pattern is ever used legitimately [and even if
> it were used legitimately, it's easy to avoid the sparse false positive
> - while in the buggy case we have a clear bug].
>
> Ingo
> --
> To unsubscribe from this list: send the line "unsubscribe linux-sparse" in
>
>
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>