Comment by mgaunard

2 years ago

Don't you have to fake the system time to do this? The time often ends up inside the binaries one way or another.

11 comments

mgaunard

Indeed time stamps are probably the most common sources of indeterminism. So common that a de-facto standard variable to fake a timestamp has been implemented in many compilers:

https://reproducible-builds.org/docs/source-date-epoch/

amelius 2 years ago

Could you name an example of how (and for what reason) this might happen?

mbakke 2 years ago

Typically part of a "version string":

    $ python3
    Python 3.10.7 (main, Jan  1 1970, 00:00:01) [GCC 11.3.0] on linux
    Type "help", "copyright", "credits" or "license" for more information.
    >>>

Perhaps a relic from when software had to be manually updated?

oever 2 years ago

On NixOS, I think the release time or commit time is used:

    $ python3
    Python 3.10.11 (main, Apr  4 2023, 22:10:32) [GCC 12.2.0] on linux
    Type "help", "copyright", "credits" or "license" for more information.
    >>>

That is more useful than the build time.

5 replies →

mgaunard 2 years ago

GCC embeds timestamps in o/gcno/gcda files to check they match.
It's mostly annoying as gcov will actively prevent you from using gcda files from a different but equivalent binary than what generated the gcno.

preisschild 2 years ago

You would just either not include the timestamp at all in all builds, or set 0, so the build date is 1970 everywhere.