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Date: Thu, 26 Nov 2009 08:59:44 +0100
To: gentoo-dev@lists.gentoo.org
Subject: Re: [gentoo-dev] mtime preservation
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From: Ulrich Mueller <ulm@gentoo.org>
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>>>>> On Wed, 25 Nov 2009, Zac Medico wrote:

>> Not non-preservation. Partial and inconsistent corruption.

> Wouldn't "loss of precision" be a more accurate description?

Yes. Or even "rounding".

> Of the known packages which require timestamp preservation, do any
> of them use sub-second precision in their timestamp comparisons?

I can speak for Emacs only, where the comparison code (in fileio.c) is
as follows:

  if (stat (SDATA (absname1), &st) < 0)
    return Qnil;

  mtime1 = st.st_mtime;

  if (stat (SDATA (absname2), &st) < 0)
    return Qt;

  return (mtime1 > st.st_mtime) ? Qt : Qnil;

It uses stat(2), therefore nanoseconds are ignored.

Ulrich