## page was renamed from ReproducibleBuilds/TimestampInPEBinaries
PE binaries [[https://code.google.com/p/corkami/wiki/PE#TimeDateStamp|contain a timestamp]].

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

= Detection =

[[attachment:cecil_0.9.5+dfsg-2.debbindiff.html|Example debbindiff output]]

= Possible work-arounds =

None yet.

Tor Browser and Bitcoin developers probably have insights on how to solve this.

Resources: [[https://stackoverflow.com/questions/17545411/is-there-any-way-to-strip-timestamp-and-date-in-a-dll-file-in-linux-is-any-tool|1]]

`strip-nondeterminism` should be taught how to handle them: [[https://github.com/FauxFaux/strip-nondeterminism/commit/a573219da4a504fe2906f2df4c23afb1f24a2f43|patch for very, very first timestamp (in the header)]]; this is not enough.

Chromium is [[http://www.chromium.org/developers/testing/isolated-testing/deterministic-builds|using]] [[https://github.com/google/syzygy/tree/master/syzygy/zap_timestamp|zap_timestamps]]. This is worth exploring.


= Solution =

== building with mono ==

[[https://bugzilla.xamarin.com/show_bug.cgi?id=26842|discusson on mono upstream bugtracker]] about enabling externally-set timestamps during the build process of PE modules. (not ready in debian yet)


== building with mingw-w64 ==

To completely drop PE timestamps, supply `-Xlinker --no-insert-timestamp` as arguments to `i686-w64-mingw32-gcc`. This works for executables, but DLLs builts like this cause problems with bound executables: updating a DLL without changing its timestamp causes bound executables to crash. See https://sourceware.org/bugzilla/show_bug.cgi?id=16887 for details.

Since `binutils-mingw-w64` version 6.2 (binary packages with versions ending in +6.2, 2.25-8+6.2 in the archive), the `--insert-timestamp` option accepts an optional timestamp expressed in milliseconds since the epoch; so something like `-Xlinker --insert-timestamp=$(date -d "$(dpkg-parsechangelog -S Date)" +%s)` will fix the timestamp to the date of the last changelog entry. This allows packages to build reproducibly but also ensures that new versions of DLLs get new timestamps. The option doesn't take any arguments on older versions of binutils or on current upstream binutils, so packages using this must build-depend on `binutils-mingw-w64-{i686,x86-64} (>= 2.25-8+6.2)`. If you decide to use this please inform `skitt@d.o` so I can help you with any changes to the option.