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Date: Tue, 21 Feb 2023 22:28:42 +0100
From: Markus Wichmann <>
Subject: Re: Re: [BUG] ioctl: overflow in implicit constant conversion

On Tue, Feb 21, 2023 at 11:57:50AM -0500, Jeffrey Walton wrote:
> In this case, I think the best course of action is to cast a,b,c to
> unsigned, then perform the shifts, and finally cast back to int. That
> is what the C standard requires. And it should not mess with the ABI.

Actually I messed up. That mostly happens already. The directions are
defined as unsigned, and the conversion to int happens implicitly. So
there is no undefined behavior. The compiler is merely warning about
nothing. That also means the only thing missing to silence the warning
would be a cast back to int. However, we have in the past never added
code just to shut up overeager warnings. Should the compiler not
suppress warnings that come from system headers?


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