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

Corinna Vinschen corinna-cygwin@cygwin.com
Tue Nov 14 21:26:00 GMT 2017

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.
> >> +    <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.

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.


Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat
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