Re: snapshot in a few hours

[Jim Meyering]

Eric Blake wrote:
> According to Eric Blake on 9/4/2009 2:06 PM:
>> According to Jim Meyering on 9/4/2009 12:12 PM:
>>>> copy.c needs to use #if LINK_FOLLOWS_SYMLINKS instead of #ifdef.
>>> Sounds good.
>>
>> How about the following two patches?
...
>>From 410eddc47c10082591b2487b234a3b5a6155daaf Mon Sep 17 00:00:00 2001
> From: Eric Blake <address@hidden>
> Date: Fri, 4 Sep 2009 13:56:16 -0600
> Subject: [PATCH 2/2] ln: add comments related to POSIX 2008
>
> * src/ln.c (ENABLE_HARD_LINK_TO_SYMLINK_WARNING): Delete.
> (do_link): Update comments per POSIX; add FIXME for -L, -P.
> ---
>  src/ln.c |   35 ++++++++++++++---------------------
>  1 files changed, 14 insertions(+), 21 deletions(-)
>
> diff --git a/src/ln.c b/src/ln.c
...
> -     POSIX 1003.1-2004 requires that ln -f A B must unlink B even on
> -     failure (e.g., when A does not exist).  This is counterintuitive,
> -     and we submitted a defect report
> -     <http://www.opengroup.org/austin/mailarchives/ag-review/msg01794.html>
> -     (2004-06-24).  If the committee does not fix the standard we'll
> -     have to change the behavior of ln -f, at least if POSIXLY_CORRECT
> -     is set.  In the meantime ln -f A B will not unlink B unless the
> -     attempt to link A to B failed because B already existed.
> +     On the surface, POSIX describes an algorithm that states that
> +     'ln -f A B' will call unlink() on B before ever attempting
> +     link() on A.  But strictly following this has the counterintuitive
> +     effect of losing the contents of B, if A does not exist.
> +     Fortunately, POSIX 2008 clarified that an application is free
> +     to fail early if it can prove continuing onwards cannot succeed,
> +     so we are justified in trying link() before blindly removing B,
> +     and calling link() twice for a successful 'ln -f'.

Looks fine, modulo:

how about adjusting via

s/and/and thus sometimes/
or s/twice/a second time,/

Otherwise, it might be seen as saying there are a total of 3 link calls.