On Fri, Feb 19, 2010 at 02:29:21PM +0300, Dan Carpenter wrote: > On Fri, Feb 19, 2010 at 11:33:30AM +0100, Bernd Petrovitsch wrote: > > On Fre, 2010-02-19 at 13:10 +0300, Dan Carpenter wrote: > > > On Fri, Feb 19, 2010 at 09:29:05AM +0100, Clemens Ladisch wrote: > > > > > This doesn't change anything, but I think it makes the code clearer. > > > > > It silences a smatch warning: > > > > > sound/pci/oxygen/oxygen_mixer.c +91 dac_mute_put(7) warn: add some parenthesis here? > > > > > > > > That message doesn't say why some parentheses should be added. > > > > And it's a question; how do I give it the answer "no"? :-) > > > > > > > > > - changed = !value->value.integer.value[0] != chip->dac_mute; > > > > > + changed = (!value->value.integer.value[0]) != chip->dac_mute; > > > > > > > > This doesn't look any clearer to me; I don't think that the unary > > > > negation operator could be thought to have lower precedence than "!=". > > > > > > Well, it's hard to argue that it's more ambiguous. :P > > But it doesn't make the code clearer - unless you are a C novice. Unary > > operators generally bind stronger than others - be it "+", "-", "!", > > "~", "*". > > I would expect kernel programmers to know that (and I don't assume > > in-depth knowledge of operator precedence rules). > > > > > > Why does smatch warn about this combination? Do such errors actually > > > > happen: > > > > > > Yep. I have made some myself when writing smatch. > > > > > > For example here are some related bugs in the current kernel. > > > > > > drivers/staging/rtl8192u/ieee80211/ieee80211_wx.c > > > 721 if (!ext->ext_flags & IW_ENCODE_EXT_GROUP_KEY && > > Well, I see potential bugs here and the if() should have been > > a) if (!(ext->ext_flags & IW_ENCODE_EXT_GROUP_KEY) && > > Yep. This is clearly what the code should say. > > The problem in the original code is that IW_ENCODE_EXT_GROUP_KEY is not > equal to either 1 or to 0. (So that means the condition in the original > code is always false). > Except the last _bit_ of IW_ENCODE_EXT_GROUP_KEY _is_ equal to one or zero and I am an idiot. But still, the original code here is wrong and your example code is correct. regards, dan carpenter _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
