Re: [PATCH] Add FAQ How do I fix find_fast_cwd warnings?

[Brian Inglis <Brian dot Inglis at SystematicSw dot ab dot ca>]

On 2017-11-14 14:26, Corinna Vinschen wrote:
> On Nov 14 13:52, Brian Inglis wrote:
>> On 2017-11-14 02:29, Corinna Vinschen wrote:
>>> On Nov 13 11:51, Brian Inglis wrote:
>>>> On 2017-11-13 10:12, Brian Inglis wrote:
>>> Please send this as `git format-patch' with commit message and all.
>>
>> One more diff for comment, and I could use some pointer on how to build htdocs
>> html from doc xml, and whether I need to concatenate the screen ulinks to get
>> them to render as a single line, which could be answered by the build.

Found I had to rebuild all of newlib-cygwin to regenerate faq.html.

>>>> +    <para>This happens when the Cygwin release you installed can not find out
>>>> +	how to get your current directory from the Windows release you are
>>>> +	using.</para>
>>> I think this paragraph raises more questions than it answers.  Of course
>>> Cygwin still can get the CWD, just not in the preferred way.  Even if
>>> you change it to more technically correct terms, it doesn't give any
>>> useful info for users.  Let's just drop it.
>>
>> Reworded to say that it the issue may not be serious, but may be a performance
>> impact, to put the issue into perspective, and give the user some context.
>> I think your comment applies best to the message itself. ;^>
>> Perhaps we should consider dropping it, or rewording to be less alarming?
> 
> The technical issue is much more complicated than just performance.  In
> a nutshell, CWD handles are opened without FILE_SHARE_DELETE by the OS,
> so we open the CWD handle by ourselves.  Starting with Vista the OS
> changed the way CWD info is stored for reasons unknown.  Performance was
> just an assumption at the time which led to the FAST_CWD name for the
> struct.  Unfortunately the new ways to handle CWDs is even less
> documented than the old ways and changed two times between five OS
> versions.  And this doesn't yet explain why we want the CWD opened with
> FILE_SHARE_DELETE at all, which requires YA nutshell.

As referred to in:
	https://blogs.msdn.microsoft.com/oldnewthing/20101109-00/?p=12323
whose comments link to:
	https://cygwin.com/ml/cygwin/2010-09/msg00342.html
and include comments by CGF and someone called Corinna wondering why their
comment was moderated [for discussing undocumented APIs] ;^>

> None of this info should be of any interest to the user struggling
> with the FAST_CWD message.  That's why I opt for dropping.

Hacked this bit up with your info and the above articles, and edited it down
again to as little as possible, in hopes of persuading you we should provide the
user at least minimal context to allow them to not worry too much about the
warning.

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

Attachment: 0001-add-FAQ-How-do-I-fix-find_fast_cwd-warnings.patch
Description: Text document