Bug 864959 – x11-wm/fvwm3-1.0.9-r1 fails to compile (lto): Colorset.h:91:20: error: type of [-Werror=lto-type-mismatch]

• Product: Gentoo Linux
• Status: CONFIRMED ---

[Description Agostino Sarubbo 2022-08-12 06:52:33 UTC]

https://blogs.gentoo.org/ago/2020/07/04/gentoo-tinderbox/

Issue: x11-wm/fvwm3-1.0.4-r2 fails to compile (lto).
Discovered on: amd64 (internal ref: lto_tinderbox)

NOTE:
This machine uses lto with CFLAGS=-flto -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing

Here is a bit of explanation:

-Werror=lto-type-mismatch:
User to find possible runtime issues in packages. It likely means the package is unsafe to build & use with LTO.
For projects using the same identifier but with different types across different files, they must be fixed to be consistent across the codebase.

-Werror=odr:
Used to find possible runtime issues in packages. These bugs are a problem anyway but may be even worse when combined with LTO. C++ code must comply with the One Definition Rule (ODR) - see https://en.cppreference.com/w/cpp/language/definition#One_Definition_Rule.

-Werror=strict-aliasing:
Used to find possible runtime issues in packages. These bugs are a problem anyway but may be even worse when combined with LTO.

Workarounds:
- If upstream is friendly and still active, file a bug upstream. For emulators, codecs, games, or multimedia packages, it may be worth just applying a workaround instead, as upstreams sometimes aren't receptive to these bugs (VALID FOR ALL).
- Use the new 'filter-lto' from flag-o-matic.eclass as it's likely to be unsafe with LTO (VALID FOR lto-type-mismatch - odr).
- Fix it yourself if interested, of course (VALID FOR ALL).
- Append-flags -fno-strict-aliasing (VALID FOR strict-aliasing).
- Use memcpy() but a union is sometimes suitable too (VALID FOR strict-aliasing).
- -fstrict-aliasing is implied by -O2, so this must be addressed in some form (VALID FOR strict-aliasing).

See also: https://marc.info/?l=gentoo-dev&m=165639574126280&w=2

[Comment 1 Agostino Sarubbo 2022-08-12 06:52:36 UTC]

Created attachment 799357 [details]
build.log

build log and emerge --info

[Comment 2 Agostino Sarubbo 2024-03-31 20:31:54 UTC]

lto_tinderbox has reproduced this issue with version 1.0.9-r1 - Updating summary.

[Comment 3 Larry the Git Cow 2024-08-15 19:07:54 UTC]

The bug has been referenced in the following commit(s):

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=a7ff4695abec63c8ef91b29d533ec89c80636190

commit a7ff4695abec63c8ef91b29d533ec89c80636190
Author:     Sam James <[e-mail]>
AuthorDate: 2024-08-15 19:04:41 +0000
Commit:     Sam James <[e-mail]>
CommitDate: 2024-08-15 19:07:03 +0000

    x11-wm/fvwm: fix patches
    
    * Use rebased ar, translucent-menus patches from bug #898918, thanks
      to Gianni Ceccarelli <[e-mail]>
    
    * Filter LTO for bug #864957 (fvwm 2.x is EOL) so unlikely to be fixed
      upstream. If 3.x gets fixed (bug #864959), we can always look at
      backporting it.
    
    Bug: https://bugs.gentoo.org/864959
    Closes: https://bugs.gentoo.org/864957
    Closes: https://bugs.gentoo.org/898918
    Signed-off-by: Sam James <[e-mail]>

 x11-wm/fvwm/files/fvwm-2.7.0-ar.patch              |  41 ++
 .../fvwm/files/fvwm-2.7.0-translucent-menus.diff   | 507 +++++++++++++++++++++
 x11-wm/fvwm/fvwm-2.7.0-r5.ebuild                   | 172 +++++++
 3 files changed, 720 insertions(+)

[Comment 4 Matt Jolly 2024-08-17 07:21:16 UTC]

I can't reproduce this with a 1.10-git meson build path. I _think_ it's resolved upstream but have no idea which change fixed it.

[Comment 5 Sam James 2024-08-17 07:22:32 UTC]

The log doesn't show it (I've filed GCC bugs before for that to be improved) but the issue is https://github.com/fvwmorg/fvwm3/blob/d26bed64c827d124b053e978f380c6b487f056eb/libs/Colorset.h#L35.

i.e. sometimes the define is set, sometimes not.

[Comment 6 Matt Jolly 2024-08-17 07:31:07 UTC]

Yeah, just managed to repro with the 1.10 tarball. Whee!

[Comment 7 Matt Jolly 2024-08-17 07:39:15 UTC]

Fixed upstream in the Meson PR by coincidence: https://github.com/fvwmorg/fvwm3/pull/996/commits/5215ec25918255e5e708420caacc1b6fa98d74f2

I'll close this off once we get that merged and redo the ebuild. If we're lucky I'll backport to fvwm2 :)