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From: Markus Wichmann <>
Subject: Re: [musl] Re: [BUG] ioctl: overflow in implicit constant conversion
Date: Wed, 22 Feb 2023 05:23:12 +0100	[thread overview]
Message-ID: <20230222042244.GH1903@voyager> (raw)
In-Reply-To: <>

On Tue, Feb 21, 2023 at 10:17:31PM -0500, Rich Felker wrote:
> Unless you're seeing something I'm not, there's no UB. The shifts take
> place on the unsigned type, and the conversion from unsigned to signed
> is implementation-defined, not undefined. The implementation-defined
> definition relevant to us is modular reduction.

Yeah, sorry, I had missed that the directions are defined as unsigned
constants. That turns any shift that might have been undefined into an
unsigned shift, where it is defined. As I said in the other mail, the
compiler is just warning about nothing here, and it should probably not
warn for system header files, anyway.

We may be able to silence the compiler by adding an explicit int
conversion to the _IOC macro. But I'm not sure if we want to set a
precedent that we will add code just to shut up overeager warnings.


  reply	other threads:[~2023-02-22  4:23 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-21  5:26 Ralph Little
2023-02-21 16:04 ` Markus Wichmann
2023-02-21 16:42   ` Florian Weimer
2023-02-21 16:53     ` alice
2023-02-21 16:57   ` Jeffrey Walton
2023-02-21 18:25     ` Ralph Little
2023-02-21 21:28     ` Markus Wichmann
2023-02-22  6:33       ` NRK
2023-02-22  3:17   ` Rich Felker
2023-02-22  4:23     ` Markus Wichmann [this message]
2023-02-22 15:53       ` Rich Felker

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