Re: [nmh-workers] Reproducible build patch

[Ralph Corderoy]

Hi Ken,

> We received the following bug report today:
>
>       http://savannah.nongnu.org/support/?109535
>
> It seems to me like reproducible builds are probably a pretty good
> idea

Yes.

> and nmh should support them, and the patch looks relatively small.

It tinkers with the hostname too.

    $ curl -sSgL 
'https://savannah.nongnu.org/support/download.php?file_id=44608' |
    > grep host
    -host=`uname -n`
    +host=${HOSTNAME:-`uname -n`}
     char *version_str = "nmh-$version$git built $date on $host";
    $

> But to be completely portable the date line should be (from here):
> https://wiki.debian.org/ReproducibleBuilds/TimestampsProposal#Bash_.2F_POSIX_shell
>
> DATE_FMT="%Y-%m-%d %T +0000"
> SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:-$(date +s)}"
> date=$(TZ=GMT0 date --date="@$SOURCE_DATE_EPOCH" "+$DATE_FMT" 2>/dev/null || 
> date -u -r "$SOURCE_DATE_EPOCH" "+$DATE_FMT" 2>/dev/null || date -u 
> "+$DATE_FMT")

https://reproducible-builds.org/specs/source-date-epoch/ says

    The value MUST be an ASCII representation of an integer with no
    fractional component, identical to the output format of date +%s. 
    If the value is malformed, the build process SHOULD exit with a
    non-zero error code. 

So I think `:-' is the wrong test, and `:' should be used.

The `+0000' is being hard-coded into date's output, rather than asking
date for the TZ to spot if the attempt to use UTC failed.

I've found some fine documentation.

    POSIX      https://manned.org/date.1p
    Coreutils  https://manned.org/date.1
               
https://www.gnu.org/software/coreutils/manual/coreutils.html#Options-for-date
    Plan9      https://manned.org/date.1plan9
    OpenBSD    https://man.openbsd.org/date
    FreeBSD    https://www.freebsd.org/cgi/man.cgi?date
    macOS¹     https://ss64.com/osx/date.html (Maybe.)

How about

    fmt='%Y-%m-%d %T %z'
    now="${SOURCE_DATE_EPOCH-$(date +%s)}"
    date="$(
        exec 2>/dev/null
        date -u -d "@$now" +"$fmt" ||
        date -u -r "$now" +"$fmt" ||
        date -u +"$fmt"
    )"
    printf '%q\n' "$fmt" "$now" "$date"

Tried with Coreutils and FreeBSD.

I think we should stick with `yyyy-mm-dd' rather than switching to
podium-style, like
https://sources.debian.org/src/nmh/1.7.1-2/debian/patches/11-repro/

-- 
Cheers, Ralph.
https://plus.google.com/+RalphCorderoy