fdatasync on Mac is a mess. What I’ve been hacking at is described in https://bugs.freedesktop.org/show_bug.cgi?id=74873 where they face the same issue.
My inclination is to steer clear of this mess. We can disable fdatasync on mac with a simple patch: $ svn diff Index: configure.in =================================================================== --- configure.in (revision 1789687) +++ configure.in (working copy) @@ -573,6 +573,11 @@ OSDIR="unix" eolstr="\\n" ;; + *darwin* ) + ac_cv_func_fdatasync="no" # Mac OS X wrongly reports it has fdatasync() + OSDIR="unix" + eolstr="\\n" + ;; *) OSDIR="unix" eolstr="\\n” Comments? Objections? — Nick Kew