X-Recipient: archive-cygwin AT delorie DOT com
DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:mime-version:in-reply-to:references:date
	:message-id:subject:from:to:content-type; q=dns; s=default; b=qO
	YlpPkOE2dvLLyRd8EewC2CNv/YmorPWZV4cBmMtokavP/vFCCkNqehim+ERgw8xH
	rRKP0svRA6GtGi5drNl6eeae7WRikh2oqoywKG6qYFWIf0d3dbqC1LNBcPzE8A5O
	ywsvrXUhD/j/Qp2dDml3BSSn7JMadaHO4QE+EkFKs=
DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:mime-version:in-reply-to:references:date
	:message-id:subject:from:to:content-type; s=default; bh=4Ixp8rpy
	/Xo02vKP6a1+aPozJow=; b=EOpJ1phtNnKl3fff8sPZzduG9rW7+XJYfeZfcVAX
	giSpr0HxBW+CSupYoy4KRExnmxWvGR0A8NN/2WLK8B0FHKTfeOX1DXb9gjTWzTB9
	ffYvKxC3ygKGNuYDqXMO7fC7U/SmcRvQGnTontlHH/s8oo0tXOedkXdY6Fi7QiOO
	iso=
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id: <cygwin.cygwin.com>
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com
Authentication-Results: sourceware.org; auth=none
X-Virus-Found: No
X-Spam-SWARE-Status: No, score=-2.2 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 spammy=anrdaemon AT yandex DOT ru, anrdaemonyandexru, U*gene.pavlovsky, sk:gene.pa
X-HELO: mail-ig0-f196.google.com
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;        d=1e100.net; s=20130820;        h=x-gm-message-state:mime-version:in-reply-to:references:date         :message-id:subject:from:to;        bh=nsD5O6n+l7m9nHRtlUBLQUlnUoYmFaASFKFQUSMKQFk=;        b=mEeYqYF136avQALV313G/5KII3Js5PEfTszvKKSbrBYT/UJLX7Z790RxJJ1FZZuEjq         R3fgB5YCk+X1XIpL0MmAxH9cVhzSJuucgvM7LkWn++iACiQGNlR94GinBQG0qSp5Mq9i         gK5jbM9JrdIacnUi3tooYRge+GA5OUhtdeBpMTpp70NVX+oV3fVINyPwRCPSGFovG0Kf         z47OGrhqArjaH06gzGnj6wli3Clfn+7GuUEFPNSMGGBu0FVf+YjmrJg3ScTDhD+6ziWQ         pB8C46skoCtwWZWvWp9Z8GuEnfXqmCQ52hRGg/XzRp85+IakJDcw+y4bFybTDaSC9W3C         Sl9w==
X-Gm-Message-State: AOPr4FXY3qXMCVFY9hnPxFRQpFeN+1NnuVxQAjPFxbLxZIaGi2654QkhEB3PejnV9FAKIS8Y1/99qn4rtWbCHQ==
MIME-Version: 1.0
X-Received: by 10.50.60.68 with SMTP id f4mr885035igr.34.1461888556260; Thu, 28 Apr 2016 17:09:16 -0700 (PDT)
In-Reply-To: <CAPTiy3OZC7acPvJRN0QtqjzfcFpnoxJkud3MTKQQVTCRr6vJVg@mail.gmail.com>
References: <CAPTiy3NUXprQL6V0+Njc2L7XfhpqtC7oWFwNMhOEFZ2OZmddoQ AT mail DOT gmail DOT com>	<1606116423 DOT 20160429020650 AT yandex DOT ru>	<CAPTiy3OZC7acPvJRN0QtqjzfcFpnoxJkud3MTKQQVTCRr6vJVg AT mail DOT gmail DOT com>
Date: Fri, 29 Apr 2016 03:09:16 +0300
Message-ID: <CAPTiy3NxLKB=jxp=-+Xx_-stS3pF813syi_Bxfp0KC8sb+kFMg@mail.gmail.com>
Subject: Re: `CYGWIN=winsymlinks:nativestrict`, `ln -s target link` fails if target doesn't exist
From: Gene Pavlovsky <gene DOT pavlovsky AT gmail DOT com>
To: cygwin AT cygwin DOT com
Content-Type: text/plain; charset=UTF-8

The list of errors that might be returned by symlink(2) mention target
only 3 times:
       EFAULT target or linkpath points outside your accessible address space.
       ENAMETOOLONG
              target or linkpath was too long.
       ENOENT A directory component in linkpath does not exist or is a
dangling symbolic link, or target or linkpath is an empty string.

So my understanding is: target must be non-empty, not too long, and
don't point outside the accessible address space. Nothing about
existence.
--Gene


On 29 April 2016 at 03:05, Gene Pavlovsky <gene DOT pavlovsky AT gmail DOT com> wrote:
> I don't know if POSIX standard has something to say about that, but
> here's a reference from GNU libc:
>
> `man 2 symlink`:
>>       A symbolic link (also known as a soft link) may point to an existing file or to a nonexistent one; the latter case is known as a dangling link.
>
> On 29 April 2016 at 02:06, Andrey Repin <anrdaemon AT yandex DOT ru> wrote:
>> Greetings, Gene Pavlovsky!
>>
>>> I have an issue to report:
>>
>>> Introduction: On a UNIX system, `ln -s target link` creates a link
>>> regardless of target's existence.
>>> This is used in some scripts, e.g. Gentoo's `run-crons` (which I also
>>> use on Cygwin) uses a symlink pointing to the running process PID as
>>> lockfile.
>>> Issue: if `CYGWIN=winsymlinks:nativestrict` env var is set, running
>>> `ln -s target link` completely fails (even though running `mklink link
>>> target` in `cmd.exe` succeeds, same as `ln -s` does on UNIX). If
>>> `CYGWIN=winsymlinks:native`, a non-native link is created.
>>
>>> So, `nativestrict` might break some (admittedly unorthodox) scripts.
>>> With `native` these script work, but still a native link would be
>>> preferrable and it is possible to create, but a non-native link is
>>> created instead.
>>
>>> Bottom line, I think the native symlink creation code should be
>>> checked and a possibility should be added to create links to
>>> non-existent targets, rather than the current behavior of failing.
>>
>> This is actually an arguable behavior, even in Linux. I can imagine the
>> behavior is "undefined" in such a case.
>> But I'll leave final say to the more experienced members of the list.
>>
>>
>> --
>> With best regards,
>> Andrey Repin
>> Friday, April 29, 2016 01:55:21
>>
>> Sorry for my terrible english...
>>

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple