Re: [PATCH PING] Honor 'SOURCE_DATE_EPOCH' when generating autoloads.

[Philipp Stephani <p.stephani2@gmail.com>]

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Eli Zaretskii <eliz@gnu.org> schrieb am So., 20. Dez. 2015 um 17:37 Uhr:

> > From: Philipp Stephani <p.stephani2@gmail.com>
> > Date: Sun, 20 Dec 2015 12:48:17 +0000
> > Cc: emacs-devel@gnu.org
> >
> > Paul Eggert <eggert@cs.ucla.edu> schrieb am Mo., 7. Dez. 2015 um 20:14
> Uhr:
> >
> >     On 12/07/2015 11:00 AM, Philipp Stephani wrote:
> >     > this would be a rather big change.
> >
> >     I suppose that depends on what one means by "big". To me it feels
> like a
> >     fairly small improvement. We've already made some progress along
> these
> >     lines in emacs-25 by removing emacs-build-system from the result of
> the
> >     emacs-version function; we just need to make more improvements like
> that.
> >
> >     It should be in 'master', though, not in 'emacs-25', as it's not
> fixing
> >     a bug.
> >
> > OK, here's a first patch that replaces system-name with a constant during
> > dumping. That eliminates one source of nondeterminism.
>
> I'm sorry, but I don't like where this is going.  I regret I didn't
> speak up earlier, but better late than never.
>
> In a nutshell, I object to losing valuable information for the benefit
> of a single specialized use case.  I have nothing against supporting
> reproducible builds as long as this removes information and data that
> is not important to us humans when developing or debugging Emacs.  For
> example, changes in loaddefs files that remove non-deterministic
> information from there or replace it with deterministic information
> are fine with me.
>
> But here we are losing information about the build system that I found
> useful more than once in the past when tracking bugs.  We have already
> removed the build system name from the bug report produced by
> report-emacs-bug (I'm going to add it back, btw, unless someone
> provides a _very_ good reason for its removal).  Earlier, we removed
> the last keystrokes, because someone was worried about their privacy,
> but couldn't be bothered to delete the sensitive parts from the bug
> report.  And your comments indicate that you intend to remove the
> build time as well, so it will be impossible to say whether a given
> binary was built before or after some change.  Where is all this
> going?
>
> I'm sorry, but I cannot agree to this slippery slope, just so we could
> support a single specialized use case.  Let's support that use case by
> providing some build-time option, either a configure-time option or a
> Makefile option, or an environment variable, or something else.  If
> someone presents a convincing case, I might even agree to have the
> release tarball build by default with that information removed
> (although I found it useful in the past when reading bug reports).
> But doing this in the development version is simply a non-starter.
> When debugging some problem that happened elsewhere, we quite often
> need every bit of information that could potentially help us, so
> removing it is out of the question.
>
> I appreciate your efforts in providing the patch, but we will have to
> find another way of supporting reproducible builds.
>
>
>
Thanks for your feedback. I'm totally happy with making this configurable
and turning it off by default. My suggestion would be to use an environment
variable EMACS_DETERMINISTIC_BUILD, which is used to initialize a new
Boolean variable `deterministic-build'. If the variable is set, the core
and Lisp packages would switch to deterministic output. I'd prefer to have
this configurable at runtime so that a single Emacs binary can be used to
produce both deterministic and non-deterministic output (e.g. for
loaddefs). Would that be OK?

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