Re: [PATCH v2 3/8] absolute_path(): reject the empty string

From: Michael Haggerty <mhagger@alum.mit.edu>
Date: Sep 9, 2012, 04:48 UTC
Message-ID: <504C1F86.4060608@alum.mit.edu>
In-Reply-To: <7vy5kmzr3e.fsf@alter.siamese.dyndns.org>

On 09/07/2012 01:09 AM, Junio C Hamano wrote:

Show 9 quoted lines

> Michael Haggerty <mhagger@alum.mit.edu> writes:
> 
>> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
>> ---
> 
> I think I asked why this matters (iow, why it is the right thing to
> do to reject an empty string, instead of treating it as "the current
> directory") in the previous round.  I would have expected to find
> the answer be above the S-o-b line here.

The reasons that the change is desirable:

1. The empty string is not a legitimate path according to POSIX; e.g.,
see Linux's path_resolution(7):

   Empty pathname
       In the original UNIX, the empty pathname referred to the current
       directory.   Nowadays  POSIX  decrees  that  an  empty  pathname
       must not be resolved successfully.  Linux returns ENOENT in this
       case.

Accordingly, comparable standard functions like realpath(3) reject the empty string.

2. The functions did not handle the empty path consistently with the way
they handled other paths (namely, the return value contained a trailing
slash).

3. This unusual behavior was undocumented.

The above points let me to the conclusion that the anomalous handling of the empty string was a bug in the implementation rather than an intended behavior. Moreover, a quick check of callers didn't turn up any that seemed to rely on the strange behavior.

Do you want a re-roll with this verbiage added to the commit messages of the two relevant commits?

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu
http://softwareswirl.blogspot.com/