Re: Compiler warning about comparing result of !!test_bit() to an integer

From: David Howells
Date: Mon Apr 27 2015 - 11:17:40 EST

Jiri Kosina <jkosina@xxxxxxx> wrote:

> gcc-5 became somehow very picky about '!!' usages. I recall quite some
> internal discussions with our gcc guys, which resulted in upstream gcc
> bugzillas being filled about gcc warning in completely legitimate cases.

I suspect it's more that it's picky about '!' usages - which covers '!!'. I'm
guessing they're trying to pick up people doing if(!x==y) when they mean
if(!(x==y)) or somesuch.
Jiri Kosina <jkosina@xxxxxxx> wrote:

> This is because we want to handle autorepeat (i.e. value 2) correctly. Now
> that you ask, it seems to me that we actually should be doing
> !!test_bit(usage->code, input->key) != !!value

I wonder if you could cast to bool instead? test_bit() possibly *should*
return a bool these days, thus rendering the '!!' unnecessary.

> to be really exact (i.e. so that we really can't have oscilating state).
> I'll think about it a little bit more, and eventually probably fix it this
> way with your Reported-by: if you are OK with that.


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