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Date: Wed, 23 Sep 2009 10:01:07 -0400
From: Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
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Subject: Re: [1.7] rename/renameat error
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On Wed, Sep 23, 2009 at 11:22:09AM +0200, Corinna Vinschen wrote:
>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.

Can we discuss these types of things in cygwin-developers, please?  It
makes searching for decisions/discussions marginally more effective if
we discuss design decisions there.

I do think, however, that before we start making changes "for efficiency"
it might be time to start thinking about doing some performance tests on
the DLL.  But that's after 1.7.1 is released.

cgf

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