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Re: [PROPOSAL] time zones and reproducible builds (was: How to make grof
From: |
Deri |
Subject: |
Re: [PROPOSAL] time zones and reproducible builds (was: How to make groff use local timezone?) |
Date: |
Tue, 22 Dec 2020 13:29:44 +0000 |
On Tuesday, 22 December 2020 03:41:14 GMT G. Branden Robinson wrote:
> > I may be misunderstanding something here, apologies if I am.
>
> No, I appreciate you speaking up--I welcome critical evaluation of my
> suggestions, especially in cases like this where I haven't carved out
> enough time to experiment and research an issue as much as is my usual
> preference.
>
Again, I fear I may be missing something obvious. My background is in the arts
not computer
science, I wanted to be an archivist when I grew up but I realised that
dribbling on the Magna
Carta or an inability to put on latex gloves may have been a hindrance to my
career!
Please can someone explain why reproducible builds are important. I assumed
that it was to
detect when the output produced from a system has changed. The purpose is to
detect changes
in the system which may have unintentionally been altered by changes to the
system.
This means that we are not interested in changes to the source code, but purely
if any changes
have occurred in the output when the system is run. After all a change to the
source code may be
intended to improve performance but unintentionally alters the output.
What is the output of groff we should be testing. It looks like we are
comparing the files that
groff's output processors produce, but this does not make sense to me. Grops
outputs the source
code of a new program. Gropdf outputs a file in the PDF language. Since these
are essentially
source files which are intended to be run at some point, diffing them just
tells us that there has
been a change in grops or gropdf, not whether that output, when run, has
changed.
Isn't the actual build output of groff marks on the page, and it is this we
should be comparing to
detect changes between one version and another, not the source code produced by
groff which
needs to run in order to produce the marks. I'm sure if the postscript or pdf
is rastered to a binary
bitmap and new and old are subtracted from each other, if there are any black
pixels left in the
image then it has failed the reproducibility test. If the result is a
completely white page there has
been no difference between the two builds, even if the post processor has had
changes which are
intended to improve the file it produces, but those changes have not altered
the result of
"running" that file.
I can't see the purpose of diffing the source code files which the post
processors produce, since
they tell you nothing except the code in the post processor has changed, not
whether the new
code has altered the marks on the page when they are run to produce their
output.
Am I missing a nuance that makes diffing the source code produced by the post
processors
useful?
Cheers
Deri
- Re: How to make groff use local timezone?, (continued)
- Re: How to make groff use local timezone?, G. Branden Robinson, 2020/12/15
- [PATCH] environment variable to make groff use UTC, G. Branden Robinson, 2020/12/15
- Re: How to make groff use local timezone?, Colin Watson, 2020/12/16
- [PROPOSAL] time zones and reproducible builds (was: How to make groff use local timezone?), G. Branden Robinson, 2020/12/20
- Re: [PROPOSAL] time zones and reproducible builds (was: How to make groff use local timezone?), Dave Kemper, 2020/12/21
- Re: [PROPOSAL] time zones and reproducible builds (was: How to make groff use local timezone?), Deri, 2020/12/21
- Re: [PROPOSAL] time zones and reproducible builds (was: How to make groff use local timezone?), Dave Kemper, 2020/12/21
- Re: [PROPOSAL] time zones and reproducible builds (was: How to make groff use local timezone?), Deri, 2020/12/21
- Re: [PROPOSAL] time zones and reproducible builds (was: How to make groff use local timezone?), G. Branden Robinson, 2020/12/21
- Re: [PROPOSAL] time zones and reproducible builds (was: How to make groff use local timezone?), Wim Stockman, 2020/12/22
- Re: [PROPOSAL] time zones and reproducible builds (was: How to make groff use local timezone?),
Deri <=
- Re: [PROPOSAL] time zones and reproducible builds (was: How to make groff use local timezone?), Colin Watson, 2020/12/23
- Re: [PROPOSAL] time zones and reproducible builds (was: How to make groff use local timezone?), G. Branden Robinson, 2020/12/28