Bug 859217 – games-simulation/flightgear-2020.3.19 fails to compile (lto): renderer_legacy.hxx:52:7: error: type struct FGRenderer violates the C++ One Definition Rule [-Werror=odr]

• Status: RESOLVED FIXED
• Product: Gentoo Linux

[Description Agostino Sarubbo 2022-07-19 07:23:31 UTC]

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

Issue: games-simulation/flightgear-2020.3.13 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

[Comment 1 Agostino Sarubbo 2022-07-19 07:23:33 UTC]

Created attachment 792233 [details]
build.log.xz

build log and emerge --info (compressed because it exceeds attachment limit, use 'xzless' to read it)

[Comment 2 Agostino Sarubbo 2022-07-19 07:23:35 UTC]

Error(s) that match a know pattern in addition to what has been reported in the summary:


FAILED: src/Main/fgfs 
fatal: not a git repository: '/var/tmp/portage/games-simulation/flightgear-2020.3.13/work/flightgear-2020.3.13/.git'
/var/tmp/portage/games-simulation/flightgear-2020.3.13/work/flightgear-2020.3.13/src/Viewer/renderer_legacy.hxx:52:7: error: type ‘struct FGRenderer’ violates the C++ One Definition Rule [-Werror=odr]

[Comment 3 Agostino Sarubbo 2022-07-26 09:01:56 UTC]

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 4 Agostino Sarubbo 2024-03-04 08:47:52 UTC]

lto_tinderbox has reproduced this issue with version 2020.3.19 - Updating summary.

[Comment 5 Eli Schwartz 2024-08-12 00:57:33 UTC]

It appears that today https://sourceforge.net/p/flightgear/codetickets/2908/ doesn't count as a valid sourceforge bug url for "see also"...

[Comment 6 Sam James 2024-08-12 00:59:54 UTC]

(In reply to Eli Schwartz from comment #5)
> It appears that today https://sourceforge.net/p/flightgear/codetickets/2908/
> doesn't count as a valid sourceforge bug url for "see also"...

https://gitweb.gentoo.org/fork/bugzilla.git/commit/?id=51ae055728e7c266e8d192c8bfd836af17eda288 doesn't include 'codetickets'...

[Comment 7 Larry the Git Cow 2024-08-12 01:16:22 UTC]

The bug has been closed via the following commit(s):

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=cdcfeb1855998c43033042d3980d38f5f695bd91

commit cdcfeb1855998c43033042d3980d38f5f695bd91
Author:     Eli Schwartz <[e-mail]>
AuthorDate: 2024-08-12 01:08:47 +0000
Commit:     Eli Schwartz <[e-mail]>
CommitDate: 2024-08-12 01:16:00 +0000

    games-simulation/flightgear: mark as LTO-unsafe
    
    Closes: https://bugs.gentoo.org/859217
    Signed-off-by: Eli Schwartz <[e-mail]>

 games-simulation/flightgear/flightgear-2020.3.19.ebuild | 7 ++++++-
 games-simulation/flightgear/flightgear-9999.ebuild      | 7 ++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)