[erlang-questions] Reproducible Erlang builds - still some time stamps (non-deterministic build)

[Mikael Pettersson]

Pjotr Prins writes:
 > Dear all,
 > 
 > At http://biobeat.org/report.html a diffoscope of two builds on GNU
 > Guix of Erlang 19.0-rc2 (made by leo). It turns out some files are
 > still different between builds. Some .script files contain time stamps
 > like:
 > 
 >     %% script generated at {2016,6,11}{19,5,37} 
 > 
 > The snmp, otp_mips, os_mon, gs modules also injects time stamps.
 > 
 > And some beam files in cosNotification and cosProperty introduce
 > differences.
 > 
 > I think none of these modules is critical and we can safely purge
 > these modules from GNU Guix so it becomes deterministic (we only
 > accept deterministic software packages) for the time being. Do you
 > agree?

No.

I acknowledge your need for deterministic builds, but the solution
ought to be to eliminate the source of the non-determinism, not the
files themselves.  So:

1. Patch whatever inserts these time stamps to not do that, or
2. Post-process affected files and remove the time stamps.