## page was renamed from ReproducibleBuilds/TimestampInStaticLibraries
`.a` files are `ar` archives. By default, they will contain a timestamp for each member (`.o`) and for the function index.

[[https://reproducible.debian.net/userContent/issues/timestamps_in_static_libraries_issue.html|Known affected packages]]

= Detection =

[[attachment:ncurses_5.9+20140913-1.debbindiff.html|Example debbindiff output]]

= Work-around =

`strip-nondeterminism` will normalize .a files the same way DebianPts:binutils does when configured for deterministic mode.

[[https://bugs.debian.org/cgi-bin/bugreport.cgi?msg=5;filename=0001-Call-strip-nondeterminism-on-static-libraries.patch;att=1;bug=774496|Example patch]]

= Solution =

GNU `ar` and other tools from DebianPts:binutils have a deterministic
mode which will use zero for UIDs, GIDs, timestamps, and use consistent
file modes for all files.

== With `--enable-deterministic-archives`  ==

DebianPts:binutils is now built with `--enable-deterministic-archives` since version 2.25-6. This means that the default mode of operation is to
create deterministic archives.

Just make sure the `U` flag is not used.

== Optional deterministic archives ==

When binutils is not built with deterministic archives by default,
build systems likely have to be patched to pass the right options
to `ar` and friends.

`ARFLAGS` can be set to `Dcvr` with many build systems to turn on the deterministic mode. Unfortunately in most cases `ranlib` will be called to create the function index. As I have yet to see a `RANLIBFLAGS` variable, it's not possible to pass `-D`. We then get a timestamp in the `.a` file.