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Date:	Wed, 23 Sep 2009 11:22:09 +0200
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
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Subject:	Re: [1.7] rename/renameat error
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On Sep 22 21:02, Eric Blake wrote:
> Eric Blake <ebb9 <at> byu.net> writes:
> 
> > > > > Cygwin 1.7 is
> > > > > detecting this situation (which is a step up from 1.5 which did the 
> rename
> > > > > anyways), but sets errno to EBUSY instead of EINVAL.
> > > > 
> > > > Thanks for catching.  Feel free to fix the rename function accordingly.
> > > 
> > > OK, I'll look into it (I don't know how large the patch will be, yet).
> > 
> > And link("a","f/.") should not create "f" as a regular file, either.  I'm 
> still 
> > looking at where to patch things.
> 
> I've got a patch in testing for both of these issues.  But while looking at 
> path.cc, I've noticed a couple of things:
> 
> The code doesn't do a very good job of remembering lengths it has already 
> seen.  For example, with relative paths, the code in normalize_posix_path does 
> cwd.get, then strchr; it seems like since cwd.get already knows how many bytes 
> it copied, that a simple API modification would pass that information back to 
> the caller so that the caller doesn't have to use strchr to find the end of the 
> string.  Anything we can do to avoid rescanning strings of known length will 
> provide speedups in path handling.

This one might be worth a shot, if it's an easy patch.

> I'm also wondering whether it is time to finally emulate Linux by requiring 
> that when doing pathname resolution of 'a/..', that 'a' actually exist (either 
> as a directory or a symlink to directory), instead of silently ignoring that 
> part of the string.  Should I go ahead and spend time working up a patch for 
> this?

This is something which I have on my TODO list for a long time, but I
never saw a simple way to implement this without losing a lot of the
already lousy performance of the path conversion.  Additionally the path
conversion code is already quite complicated and I fear the unwanted
side effects such a change could have.  Therefore, I tend to think of
this as a welcome post-1.7.1 change.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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