Danny Milosavljevic <dannym@scratchpost.org> writes:

> Fixes <https://bugs.gnu.org/27593>.
>
> * gnu/packages/groff.scm (groff)[source]: Remove timestamps.
> ---
>  gnu/packages/groff.scm | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/gnu/packages/groff.scm b/gnu/packages/groff.scm
> index 46e1ccf23..1a74194a6 100644
> --- a/gnu/packages/groff.scm
> +++ b/gnu/packages/groff.scm
> @@ -40,7 +40,23 @@
>              (uri (string-append "mirror://gnu/groff/groff-" version
>                                  ".tar.gz"))
>              (sha256 (base32
> -                     "1998v2kcs288d3y7kfxpvl369nqi06zbbvjzafyvyl3pr7bajj1s"))))
> +                     "1998v2kcs288d3y7kfxpvl369nqi06zbbvjzafyvyl3pr7bajj1s"))
> +            (modules '((guix build utils)))
> +            (snippet
> +             '(begin
> +                (substitute* "mdate.sh"
> +                 (("^LANGUAGE=") "
> +
> +echo \"1 Jan 1970\"
> +exit 0
> +
> +"))

It would be more obvious what's going on if we substitute the "mdate.sh"
invocation from the Makefile instead. OTOH, this is more
future-proof. No strong opinion, but feels a bit "hacky".

Note that you can use \n here.

> +                (substitute* '("src/devices/grops/ps.cpp"
> +                               "src/devices/grohtml/post-html.cpp"
> +                               "src/roff/troff/input.cpp")
> +                  (("time\\(0\\)") "0"))
> +                (substitute* "src/devices/gropdf/gropdf.pl"
> +                  (("\\(time\\)") "(0)"))))))

Are all of these really a cause of indeterminism in the build process?
It looks like this could make "legitimate" uses of groff return epoch 0
at runtime, I'm not sure if that is okay.

Which output files are fixed by these substitutions? Are there other
ways to deal with the indeterminism, e.g. substitute them in place?