Bug 879323 – sci-physics/root-6.26.08 fails to compile (lto): zebra.f:767:72: error: type of [-Werror=lto-type-mismatch]

• Product: Gentoo Linux
• Status: RESOLVED FIXED

[Description Agostino Sarubbo 2022-11-03 11:44:07 UTC]

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

Issue: sci-physics/root-6.26.08 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 2022-11-03 11:44:10 UTC]

Created attachment 826869 [details]
build.log.xz

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

[Comment 2 Guilherme Amadio 2022-11-03 16:13:14 UTC]

Issue filed upstream at https://github.com/root-project/root/issues/11657.

[Comment 3 Guilherme Amadio 2022-11-04 10:23:38 UTC]

Can you please try also with USE=-fortran? For context, the cernlib implementation in ROOT is legacy code for things that used to be part of the old CERN library (i.e. sci-physics/cernlib, which is long gone), and sci-physics/paw (also long gone) (see the page for PAW at https://en.wikipedia.org/wiki/Physics_Analysis_Workstation, since the old website for it at CERN is gone). One of the things in minicern within ROOT is support for converting old hbook files from PAW into ROOT format. Nowadays there are likely no users for this code anymore, it's just kept there as legacy and not maintained. If these Fortran bits are the only place where LTO is a problem, I would strongly suggest just using USE=-fortran, as I don't expect these to be fixed upstream. That said, we will accept a patch if someone submits a fix.

[Comment 4 Larry the Git Cow 2024-03-10 12:16:38 UTC]

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

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=5401a0bca754883a3466da1c35ccabab423190ee

commit 5401a0bca754883a3466da1c35ccabab423190ee
Author:     Guilherme Amadio <[e-mail]>
AuthorDate: 2024-03-09 16:47:10 +0000
Commit:     Guilherme Amadio <[e-mail]>
CommitDate: 2024-03-10 12:16:25 +0000

    sci-physics/root: filter lto flags, bug #879323
    
    Closes: https://bugs.gentoo.org/879323
    
    Signed-off-by: Guilherme Amadio <[e-mail]>

 sci-physics/root/root-6.28.12.ebuild   | 5 ++++-
 sci-physics/root/root-6.30.04.ebuild   | 5 ++++-
 sci-physics/root/root-6.30.9999.ebuild | 7 +++++--
 sci-physics/root/root-9999.ebuild      | 7 +++++--
 4 files changed, 18 insertions(+), 6 deletions(-)