[PATCH] ln: use gnulib's link module, to work around Solaris 10 deficiency

[Jim Meyering]

Jim Meyering wrote:
> Eric Blake wrote:
>> According to Jim Meyering on 9/10/2009 6:24 AM:
>>>
>>> Currently, we're at gnulib (v0.0-2549-g2c90f1a) for the submodule.
>>> None of the patches since then seemed to be essential to coreutils
>>> on non-mingw/cygwin systems.  Let me know if you'd like to use
>>> a newer version.
>>
>> Updating to v0.0-2560-g7a3196b would allow working around a Solaris 10 bug
>> where link("a","b/") succeeds and creates a file "b", rather than failing
>> because the directory "b/" does not exist.  This fixes behavior visible in
>> "ln -T a b/".
>
> That's tempting.
> I've confirmed the problem, and wrote a test to exercise the bug/fix.
> I'm testing this now...

Here's a complete patch.
It passes the new test on Solaris 10,
while without the gnulib update, it would fail that one.

If this passes as well on a couple more systems, I'll push it.

As I write this, I realized that a slightly more likely
scenario is also fixed:

    link f no-such-file/

I'll update NEWS and the log to mention "link", too.

Comments welcome.

>From fb19a28755f62f9f89ac0ff98638c49ab942589e Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Thu, 10 Sep 2009 17:51:44 +0200
Subject: [PATCH] ln: use gnulib's link module, to work around Solaris 10 
deficiency

Before this change, :>f; ln -T f no-such/ would succeed on Solaris 10.
After it, ln fails, as it should: ln: accessing `z/': Not a directory
* bootstrap.conf (gnulib_modules): Add "link".
* tests/ln/slash-decorated-nonexistent-dest: New test.
* tests/Makefile.am (TESTS): Add it.
* NEWS (Portability): Mention the improvement.
---
 NEWS                                      |    8 ++++++
 bootstrap.conf                            |    1 +
 tests/Makefile.am                         |    1 +
 tests/ln/slash-decorated-nonexistent-dest |   34 +++++++++++++++++++++++++++++
 4 files changed, 44 insertions(+), 0 deletions(-)
 create mode 100755 tests/ln/slash-decorated-nonexistent-dest

diff --git a/NEWS b/NEWS
index 26dcd59..2b35719 100644
--- a/NEWS
+++ b/NEWS
@@ -45,6 +45,14 @@ GNU coreutils NEWS                                    -*- 
outline -*-
   (i.e., not inotify-based) implementation.
   [bug introduced in coreutils-7.5]

+** Portability
+
+  ln -T f z/; given an existing file, f, and nothing named "z", that
+  command would mistakenly create "z" as a link to "f" on Solaris 10,
+  due to the way their link syscall works.  Now, even on that type
+  of system, that ln command reports the error, as it should:
+  ln: accessing `z/': Not a directory
+
 ** New features

   cp --reflink accepts a new "auto" parameter which falls back to
diff --git a/bootstrap.conf b/bootstrap.conf
index 7ec4b3b..c2bf753 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -130,6 +130,7 @@ gnulib_modules="
   lchown
   lib-ignore
   linebuffer
+  link
   link-follow
   long-options
   lstat
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 1de53bf..7a20e0c 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -345,6 +345,7 @@ TESTS =                                             \
   ln/hard-backup                               \
   ln/misc                                      \
   ln/sf-1                                      \
+  ln/slash-decorated-nonexistent-dest          \
   ln/target-1                                  \
   ls/abmon-align                               \
   ls/color-clear-to-eol                                \
diff --git a/tests/ln/slash-decorated-nonexistent-dest 
b/tests/ln/slash-decorated-nonexistent-dest
new file mode 100755
index 0000000..afbbd06
--- /dev/null
+++ b/tests/ln/slash-decorated-nonexistent-dest
@@ -0,0 +1,34 @@
+#!/bin/sh
+# ensure that touch f; ln -T f no-such-file/ does not mistakenly succeed
+
+# Copyright (C) 2009 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+if test "$VERBOSE" = yes; then
+  set -x
+  ln --version
+fi
+
+. $srcdir/test-lib.sh
+
+touch f || framework_failure
+
+fail=0
+
+# Before coreutils-7.6, this would succeed on Solaris 10
+ln -T f no-such-file/ && fail=1
+test -e no-such-file && fail=1
+
+Exit $fail
--
1.6.5.rc0.164.g5f6b0