linux-kernel - Re: [for-linus][PATCH 01/10] tracing: Suppress sparse warnings triggered by is_signed

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Date:   Wed, 24 Aug 2022 04:20:04 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Bart Van Assche <bvanassche@....org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: Re: [for-linus][PATCH 01/10] tracing: Suppress sparse warnings
 triggered by is_signed_type()

On Wed, Aug 24, 2022 at 04:10:25AM +0100, Al Viro wrote:
> *IF* you want to go that way, I would suggest a new return value for
> restricted_binop() ("comparison with magical value"), with
> something like
> 		switch (restricted_binop(op, ctype)) {
> 		case 1:
> 		....
> 
> 		default:
> 			break;
> 		case 4:
> 			// comparison with magic value:
> 			// quietly go for underlying type, if not fouled
> 			// if fouled, just return NULL and let the caller
> 			// deal with that - loudly.
> 			if (!(lclass & rclass & TYPE_FOULED))

 			if (!((lclass | rclass) & TYPE_FOULED))

that is - we don't need both of them being fouled to trigger a warning;
either one should suffice.