Bug 854186 – app-admin/prelude-manager-5.2.0-r1 fails to compile (lto): ev.h:722:52: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

• Product: Gentoo Linux
• Status: RESOLVED FIXED

[Description Agostino Sarubbo 2022-06-25 08:17:23 UTC]

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

Issue: app-admin/prelude-manager-5.2.0-r1 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 2022-06-25 08:17:26 UTC]

Created attachment 787490 [details]
build.log

build log and emerge --info

[Comment 2 Agostino Sarubbo 2022-06-25 08:17:27 UTC]

Created attachment 787493 [details]
1-config.log

1-config.log

[Comment 3 Agostino Sarubbo 2022-07-26 09:00:08 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 Larry the Git Cow 2022-12-20 14:26:31 UTC]

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

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=064ad0eacceb8a748494c3f9c50de6e924aaae53

commit 064ad0eacceb8a748494c3f9c50de6e924aaae53
Author:     Jakov Smolić <[e-mail]>
AuthorDate: 2022-12-20 13:53:03 +0000
Commit:     Jakov Smolić <[e-mail]>
CommitDate: 2022-12-20 14:25:27 +0000

    app-admin/prelude-manager: treeclean
    
    Closes: https://bugs.gentoo.org/854186
    Closes: https://bugs.gentoo.org/778896
    Closes: https://bugs.gentoo.org/728546
    Signed-off-by: Jakov Smolić <[e-mail]>

 app-admin/prelude-manager/Manifest                 |  1 -
 .../files/prelude-manager-3.1.0-run.patch          | 13 ----
 .../prelude-manager/files/prelude-manager.initd    | 25 --------
 .../prelude-manager/files/prelude-manager.run      |  4 --
 .../prelude-manager/files/prelude-manager.service  | 14 -----
 app-admin/prelude-manager/metadata.xml             | 16 -----
 .../prelude-manager-5.2.0-r1.ebuild                | 73 ----------------------
 profiles/package.mask                              |  6 --
 8 files changed, 152 deletions(-)