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Date:	Fri, 9 Mar 2012 10:47:54 -0500
From:	Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: rebase keeps last modification time of DLL unchanged
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On Fri, Mar 09, 2012 at 09:43:07AM +0100, Corinna Vinschen wrote:
>On Mar  8 21:37, Christian Franke wrote:
>> Corinna Vinschen wrote:
>> >On Mar  7 23:07, Christian Franke wrote:
>> >>The rebase tool does not change last modification timestamp of each
>> >>DLL even if its data has changed. This is likely because Windows
>> >>"may" not update the timestamp for files written through a memory
>> >>mapped view.
>> >>
>> >>Is this an intended behavior of rebase?
>> >Why should rebase change the timestamp?  Apart from the rebasing, the
>> >DLL is still the same.  If you want to know when it has been last
>> >rebased, you can look into the file header:
>> >
>> >   $ objdump -p cygiconv-2.dll | grep 'Time/Date[^ ]'
>> >   Time/Date               Tue Mar  6 23:24:12 2012
>> >
>> 
>> It depends: Changing data without changing st_mtime avoids
>> (unneeded|required) file copies during incremental backups, rsync,
>> robocopy, ...
>> 
>> rebase does not explicitly (re)set the timestamp after rebasing. Is
>> this by design?
>> 
>> It relies on weakly defined Windows behavior: "When modifying a file
>> through a mapped view, the last modification timestamp *may* not be
>> updated automatically."
>> http://msdn.microsoft.com/en-us/library/windows/desktop/aa366563.aspx
>
>Well, let me put it like this.  Rebase just does its job.  It doesn't
>actually care for the file timestamp, only for the file header
>timestamps.  This is not by design, it's just as it is.  So the next
>question is obvious.  Do you think it should change the timestamp or
>not?  Why?  A patch is simple and I have it actually already waiting in
>the scenery.

I don't think the default should change but maybe an option could be
added for people who want to see updated times.

cgf

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