Building Tor from source brings up this warning several times: > "ar: `u' modifier ignored since `D' is the default (see `U')" a lot. The fix is to change the according line in Makefile.in to `ARFLAGS=crD`. (easy to find with `grep -n "ARFLAGS =" Makefile.in`) Since Makefile.in is created by the `./configure` script, the [default flags need to be changed](https://www.gnu.org/software/automake/manual/automake.html#A-Library): > "ARFLAGS will default to cru; you can override this variable by setting it in your Makefile.am or by AC_SUBSTing it from your configure.ac." Before distributing Tor with it, we need to check if any platform build breaks. For example versions before [binutils v2.24-20](https://bugzilla.redhat.com/show_bug.cgi?id=1124342#c4) / [GNU Make 4](https://savannah.gnu.org/forum/forum.php?forum_id=7749) (2013-10-09). I did not check for OSX and BSD yet. The options -D / -U [were introduced](https://bugzilla.redhat.com/show_bug.cgi?id=1195883#c3) in [January 2013](https://lists.gnu.org/archive/html/info-gnu/2003-12/msg00001.html). For debian see [Bug 798913](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=798913) (and the [Debian changelog](https://salsa.debian.org/srivasta/make-dfsg/blob/master/debian/changelog)): > binutils upstream provides a configure option '--enable-deterministic-archives', which makes this behaviour the default, though it can still be disabled at runtime via the 'u' switch, in case someone wants to use ar to pack non-library files in an archive and cares about the metadata. References * https://www.mail-archive.com/bug-automake@gnu.org/msg04226.html