On Monday, June 10, 2019 9:06:30 AM CEST Kalle Valo wrote: > Christian Lamparter <chunkeey@xxxxxxxxx> writes: > > > This patch fixes a noisy warning triggered by -Wenum-compare > > > > |main.c:1390:31: warning: comparison between ‘enum nl80211_ac’ > > | and ‘enum ar9170_txq’ [-Wenum-compare] > > | BUILD_BUG_ON(NL80211_NUM_ACS > __AR9170_NUM_TXQ); > > | ^ > > | [...] > > > > This is a little bit unfortunate, since the number of queues > > (hence NL80211_NUM_ACS) is a constant based on the IEEE 802.11 > > (much like IEEE80211_NUM_ACS) and __AR9170_NUM_TXQ is more or > > less defined by the AR9170 hardware. > > Is the warning enabled by default? TBH I'm not seeing how useful this > warning is for kernel development. It is included in the "-Wall" (which is coming from "KBUILD_CFLAGS" in the main Makefile). I tried debian's gcc starting from 4.6 to the lastest 8.3. They all complain about it in various degrees. https://gcc.gnu.org/onlinedocs/gcc-4.6.0/gcc/Warning-Options.html#Warning-Options > > --- a/drivers/net/wireless/ath/carl9170/main.c > > +++ b/drivers/net/wireless/ath/carl9170/main.c > > @@ -1387,7 +1387,7 @@ static int carl9170_op_conf_tx(struct ieee80211_hw *hw, > > int ret; > > > > BUILD_BUG_ON(ARRAY_SIZE(ar9170_qmap) != __AR9170_NUM_TXQ); > > - BUILD_BUG_ON(NL80211_NUM_ACS > __AR9170_NUM_TXQ); > > + BUILD_BUG_ON((size_t)NL80211_NUM_ACS > (size_t)__AR9170_NUM_TXQ); > > IMHO this just makes the code worse. Does it make sense to workaround > (stupid) compiler warnings like this? True. What's worse: This isn't really code. The BUILD_BUG_ON Macro is there to guard but it's getting compiled away. I could also just drop it.
