linux-kernel - Re: [BUG] Generic syscalls -- chmod vs. fchmodat

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Date:	Mon, 24 Jan 2011 16:32:22 -0500
From:	Mike Frysinger <vapier@...too.org>
To:	libc-ports@...rceware.org
Cc:	Roland McGrath <roland@...hat.com>, linasvepstas@...il.com,
	Chris Metcalf <cmetcalf@...era.com>,
	Arnd Bergmann <arnd@...db.de>,
	GLIBC Devel <libc-alpha@...rceware.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [BUG] Generic syscalls -- chmod vs. fchmodat

On Monday, January 24, 2011 16:05:14 Roland McGrath wrote:
> POSIX says "A null pathname shall not be successfully resolved."  This
> applies to relative pathnames too, and a file name argument to an *at
> function using AT_FDCWD is a relative pathname.  So I think there is no
> situation at all in which the empty string should resolve to anything.
> It's generally in the domain of the kernel to enforce these kinds of rules,
> so I think that having the kernel fail with ENOENT for all empty-string
> cases is the right thing to do.

typically, Linux isnt hard pressed to enforce POSIX semantics.  that barrier 
is the realm of glibc.  the *at functions as implemented by Linux can provide 
neat semantics where you can open a directory, process a bunch of files via 
that fd, and then turn around and operate on the dir itself with NULL or "" 
paths.  plus, once Linux has shipped with a syscall behavior set, Linus really 
doesnt let people change it.  which means it's back on glibc's head to provide 
POSIX semantics to application.
-mike

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