Bug 2346007

Linking upstream bug report and adding several KDE folks to CC.

Created attachment 2076776 [details]
ICC profile that reproduces the issue

I've attached the ICC profile from the upstream report that reproduces the issue.

Proposed as a Blocker for 42-beta by Fedora user ngompa using the blocker tracking app because:

 This GCC error results in core functionality of the compositor for the release-blocking KDE desktop to be broken.

Discussed on 2025-02-24 in a blocker review meeting [1]:

!agreed 2346007 - AcceptedBetaFE AcceptedFinalBlocker - This is quite difficult to work around and a complete showstopper for a general user. Therefore it is accepted as a blocker.

[1] https://meetbot.fedoraproject.org/blocker-review_matrix_fedoraproject-org/2025-02-24/f42-blocker-review.2025-02-24-17.01.log.html

Looking at https://bugs.kde.org/show_bug.cgi?id=499789#c27 I see:

> core: Fix initialization of IccProfile::s_connectionSpace
>
> Colorimetry constants can be initialized after IccProfile::s_connectionSpace
> when LTO is enabled. It's okay with the C++ standard.
>
> As a way around it, this change moves the CIEXYZD50 constant to the
> IccProfile where it's actually needed.
>
> We need to reconsider how the constants are defined, e.g. have static
> getters or use constexpr. But as a short term solution, this should be
> fine.
>
> Co-authored-by: Xaver Hugl <xaver.hugl>
>
> M  +0    -2    src/backends/wayland/color_manager.cpp
> M  +0    -8    src/core/colorspace.cpp
> M  +0    -1    src/core/colorspace.h
> M  +8    -1    src/core/iccprofile.cpp
>
> https://invent.kde.org/plasma/kwin/-/commit/6d6667fc2a3f0a5e51676be267a5a8e1ce3c1337

I don't see any input from other GCC developers on this, but *if* I'm reading the above right, it sounds like:
(a) KWin was relying on two initializations happening in a particular order that wasn't guaranteed by the C++ standard, and which happened to stop happening with GCC with LTO, and
(b) that upstream KWin has fixed this.

If so, then it sounds like this a bug in KWin rather than in GCC.

Reassigning to kwin; please reassign back if I've misunderstood the above (which could well be the case)

Your analysis is spot on based on IRC discussion with the KWin developers at the time.

(There was/is the aliasing bug which there's a fix sitting for on a branch, I'll chase that up if they forget, but it's not relevant to this other than noticing it while investigating.)

Setting POST, on the basis that there's apparently an upstream kwin commit that fixes this, which we would just need to backport?

FEDORA-2025-f31d078526 (bluedevil-6.3.2-1.fc42, breeze-gtk-6.3.2-1.fc42, and 67 more) has been submitted as an update to Fedora 42.
https://bodhi.fedoraproject.org/updates/FEDORA-2025-f31d078526

FEDORA-2025-f31d078526 has been pushed to the Fedora 42 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2025-f31d078526`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2025-f31d078526

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Discussed on 2025-03-03 in a blocker review meeting [1]:

!info per Conan Kudo this is substantively addressed for Beta. it will either be closed, or the blocker nomination will be unset

[1] https://meetbot.fedoraproject.org/blocker-review_matrix_fedoraproject-org/2025-03-03/f42-blocker-review.2025-03-03-17.00.log.html

FEDORA-2025-f31d078526 (applet-window-buttons-0.12.0^20240405.3263828-4.fc42, bluedevil-6.3.2-1.fc42, and 68 more) has been pushed to the Fedora 42 stable repository.
If problem still persists, please make note of it in this bug report.

The needinfo request[s] on this closed bug have been removed as they have been unresolved for 120 days