[PATCH v2] close_range: fd and max_fd are unsigned

[Alyssa Ross]

On Wed, May 05, 2021 at 08:14:13PM +0300, Dmitry V. Levin wrote:
> On Wed, May 05, 2021 at 05:11:29PM +0000, Alyssa Ross wrote:
> > On Wed, May 05, 2021 at 07:51:00PM +0300, Dmitry V. Levin wrote:
> > > On Tue, May 04, 2021 at 07:53:59PM +0000, Alyssa Ross wrote:
> > > > The distinction is important, because close_range(2) says that having
> > > > max_fd < fd is an error, but if you give the kernel 1U + INT_MAX as
> > > > max_fd, it'll interpret it as unsigned.
> > > >
> > > > Since we're working with ranges of file descriptors here, the
> > > > particular properties of only the start and end file descriptors
> > > > aren't really relevant, so it doesn't matter that we're losing fancy
> > > > file descriptor printing in making this change.
> > > > ---
> > > > v1: https://lists.strace.io/pipermail/strace-devel/2021-March/010459.html
> > > [...]
> > > >  int
> > > >  main(void)
> > > >  {
> > > > -	SKIP_IF_PROC_IS_UNAVAILABLE;
> > > > +	k_close_range(4294967294, 4294967295, 1);
> > > > +	printf("close_range(4294967294, 4294967295, 0x1 /* CLOSE_RANGE_??? */) = %s\n", errstr);
> > > >
> > > > -	const int fd0 = dup(0);
> > > > -	const int fd7 = dup(7);
> > > > -	const int fd7_min = MIN(7, fd7);
> > > > -	const int fd7_max = MAX(7, fd7);
> > > > +	k_close_range(4294967295, 4294967294, 2);
> > > > +	printf("close_range(4294967295, 4294967294, CLOSE_RANGE_UNSHARE) = %s\n", errstr);
> > > >
> > > > -	k_close_range(-2, -1, 1);
> > >
> > > Why do you replace -2 and -1 with 4294967294 and 4294967295?
> > > Aren't -2U and -1U more readable?
> >
> > In isolation, yes, but then the next line (the printf) has to use the 4294967294
> > version, so I thought it would be confusing to be jugging the two
> > different representations.
> >
> > Would you prefer this?
> >
> > 	k_close_range(-2U, -1U, 2);
> > 	printf("close_range(4294967295, 4294967294, CLOSE_RANGE_UNSHARE) = %s\n", errstr);
>
> I'd actually prefer this:
>
> 	k_close_range(-2U, -1U, 2);
> 	printf("close_range(%u, %u, CLOSE_RANGE_UNSHARE) = %s\n",
> 	       -2U, -1U, errstr);

Ah, of course.  Not sure why I didn't think of that...

I'll have a v3 for you shortly.
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