[PATCH v2] close_range: fd and max_fd are unsigned

[Dmitry V. Levin]

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);


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