Date: Mon, 31 Dec 2018 21:52:25 -0800 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: Pedro Giffuni <pfg@freebsd.org> Cc: freebsd-numerics@freebsd.org Subject: Re: Undefined Behavior in lib/msun/src/e_pow.c (was Re: New math library from ARM) Message-ID: <20190101055225.GA5982@troutmask.apl.washington.edu> In-Reply-To: <d01c8770-5431-0634-4ecc-37069ff76458@FreeBSD.org> References: <797a7755-db93-1b9c-f3b9-8850d948e098@FreeBSD.org> <20181231151904.GB823@troutmask.apl.washington.edu> <20181231152230.GC823@troutmask.apl.washington.edu> <06c8b6a2-ed26-f255-3947-c79b593a9dea@FreeBSD.org> <20190101045425.GA5767@troutmask.apl.washington.edu> <d01c8770-5431-0634-4ecc-37069ff76458@FreeBSD.org>
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On Tue, Jan 01, 2019 at 12:14:38AM -0500, Pedro Giffuni wrote:
>
> > I'll defer to Bruce on this. My only comments are
> > 1) declarations belong at the top of the file where all declarations occur
>
> Modern standards let you declare variables within blocks. For style we
> do prefer to start the function with them but in this case we can't.
I'am aware of what modern standards allow. I'm also
aware of the code style of fdlibm, which I think
should be maintain.
> > 2) j is already declared as int32_t
> And it has to be a signed integer: we later check for negative values.
Yeah, I know. That's why I pointed out the collision.
> > 3) uint32_t should be written as u_int32_t.
>
> No, uint32_t is the standard type, u_int32_t is a BSDism. Also, the file
> consistently uses uint32_t.
Ah, no. e_pow.c uses u_int32_t on line 107. This would be easy
to see if all declarations are grouped together. In additional,
don't you need to include stdint.h to get uint32_t?
% grep uint32_t /usr/src/lib/msun/src/e_pow.c
% grep u_int32_t /usr/src/lib/msun/src/e_pow.c
u_int32_t lx,ly;
n = ((u_int32_t)hx>>31)-1;
Code churn to placate lint for an event that cannot occur
seems dubious to me.
--
Steve
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