Bug#1030785: -ffile-prefix-map option and reproducibility

[Vagrant Cascadian]

On 2023-02-08, Stéphane Glondu wrote:
> Thank you all for your answers!
>
> Using:
>
>    DEB_BUILD_MAINT_OPTIONS=reproducible=-fixfilepath,-fixdebugpath
>
> makes the package unreproducible in another way that seems difficult to fix.

Most likely reintroducing the things that the -ffile-prefix-map and
-fdebug-prefix-map was effectively removing...


We track these kinds of issues with the "records build flags" issue,
which has a description of the problem and links to more information:

  https://tests.reproducible-builds.org/debian/issues/unstable/records_build_flags_issue.html

There are some potential fixes to the issue more fundamentally, but they
are currently stalled out... one of which I should probably spend some
time on after bookworm release...


You had earlier asked when this was enabled, this can mostly be found in
the dpkg changelog:

fixfilepath (a.k.a. -ffile-prefix-map) Enabled by default:

dpkg (1.20.6) unstable; urgency=medium
...

  * dpkg-buildflags: Enable reproducible=fixfilepath by default.  Thanks
    to Vagrant Cascadian <vagrant at reproducible-builds.org>.  See
    https://lists.debian.org/debian-devel/2020/10/msg00222.html.
    Closes: #974087
...
 -- Guillem Jover <guillem at debian.org>  Fri, 08 Jan 2021 04:39:40 +0100


fixfilepath (a.k.a. -ffile-prefix-map) feature added, and enabled in
reproducible builds infrastructure soon after:

dpkg (1.19.1) unstable; urgency=medium
...
    - Dpkg::Vendor::Debian: Add fixfilepath support to reproducible feature.
...
 -- Guillem Jover <guillem at debian.org>  Wed, 26 Sep 2018 15:13:22 +0200


fixdebugpath (a.k.a. -fdebug-prefix-map) enabled by default:

dpkg (1.18.10) unstable; urgency=medium
...
    - Enable fixdebugpath build flag feature by default.
      Thanks to Mattia Rizzolo <mattia at debian.org>. Closes: #832179
...
 -- Guillem Jover <guillem at debian.org>  Sun, 31 Jul 2016 12:57:02 +0200


fixdebugpath (a.k.a. -fdebug-prefix-map) feature added, and presumably
enabled in reproducible builds infrastructure soon after:

dpkg (1.18.5) unstable; urgency=medium
...
    - Add fixdebugpath to reproducible feature in Dpkg::Vendor::Debian.
      Thanks to Daniel Kahn Gillmor <dkg at fifthhorseman.net>. Closes:
      #819194
...
 -- Guillem Jover <guillem at debian.org>  Mon, 02 May 2016 04:14:57 +0200


Of course, this is only for packages respecting dpkg-buildflags.


> Le 07/02/2023 à 19:12, Mattia Rizzolo a écrit :
>> I actually propose to you to filter out the whole option from being
>> saved. [...]
>
> I've gone this way, and managed to make the package reproducible, at 
> least with the build path variation.

Glad that works!


> I will upload the fixed ocaml package when the current batch of related 
> packages waiting in unstable migrates to testing, hopefully in 4 days.

Thanks!


live well,
  vagrant
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