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

Ingo Molnar
2008-03-05T06:39:31Z

* 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