Add a note about lack of nanosecond precision in movefile(). (trunk r14900)

svn path=/main/branches/2.1.7/; revision=14905

diff --git a/pym/portage/__init__.py b/pym/portage/__init__.py
index e314654f46c4ed129698b2567483fa612f7e2bb8..e0c88813af1fb2189422079f37df647bd5c4c735 100644 (file)
--- a/pym/portage/__init__.py
+++ b/pym/portage/__init__.py
@@ -7566,6 +7566,9 @@ def movefile(src, dest, newmtime=None, sstat=None, mysettings=None,
                if hardlinked:
                        newmtime = long(os.stat(dest).st_mtime)
                else:
+                       # Note: It is not possible to preserve nanosecond precision
+                       # (supported in POSIX.1-2008 via utimensat) with the IEEE 754
+                       # double precision float which only has a 53 bit significand.
                        if newmtime is not None:
                                os.utime(dest, (newmtime, newmtime))
                        else: