Bug 862705 – sci-libs/ginkgo-1.6.0 fails to compile (lto): extended_float.hpp:321:61: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

• Product: Gentoo Linux
• Status: RESOLVED FIXED

[Description Agostino Sarubbo 2022-08-01 07:56:07 UTC]

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

Issue: sci-libs/ginkgo-1.4.0-r3 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 2022-08-01 07:56:10 UTC]

Created attachment 796447 [details]
build.log

build log and emerge --info

[Comment 2 Agostino Sarubbo 2022-08-01 07:56:12 UTC]

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


-- Could NOT find PAPI (missing: PAPI_LIBRARY PAPI_INCLUDE_DIR) 
FAILED: reference/CMakeFiles/ginkgo_reference.dir/preconditioner/jacobi_kernels.cpp.o 
FAILED: reference/CMakeFiles/ginkgo_reference.dir/solver/cb_gmres_kernels.cpp.o 
fatal: not a git repository (or any parent up to mount point /var/tmp)
/var/tmp/portage/sci-libs/ginkgo-1.4.0-r3/work/ginkgo-1.4.0/core/base/extended_float.hpp:321:61: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

[Comment 3 Agostino Sarubbo 2024-03-23 09:39:53 UTC]

lto_tinderbox has reproduced this issue with version 1.6.0 - Updating summary.

[Comment 4 Larry the Git Cow 2024-08-01 03:15:08 UTC]

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

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=12772e77c1002179e87918b5af37ac1d52b64f78

commit 12772e77c1002179e87918b5af37ac1d52b64f78
Author:     Eli Schwartz <[e-mail]>
AuthorDate: 2024-08-01 00:16:45 +0000
Commit:     Eli Schwartz <[e-mail]>
CommitDate: 2024-08-01 03:14:17 +0000

    sci-libs/ginkgo: mark as LTO-unsafe, strict-aliasing unsafe
    
    Closes: https://bugs.gentoo.org/862705
    Signed-off-by: Eli Schwartz <[e-mail]>

 sci-libs/ginkgo/ginkgo-1.4.0-r3.ebuild | 10 +++++++++-
 sci-libs/ginkgo/ginkgo-1.6.0.ebuild    | 10 +++++++++-
 sci-libs/ginkgo/ginkgo-1.8.0.ebuild    | 10 +++++++++-
 3 files changed, 27 insertions(+), 3 deletions(-)