Bug 879327 – sci-mathematics/z3-4.11.2 fails tests (LTO-SYSTEM): hwf.cpp:106:21: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

• Product: Gentoo Linux
• Status: RESOLVED FIXED

[Description Agostino Sarubbo 2022-11-03 12:08:18 UTC]

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

Issue: sci-mathematics/z3-4.11.2 fails tests (LTO-SYSTEM).
Discovered on: amd64 (internal ref: lto_tinderbox)

NOTE:
(LTO-SYSTEM) in the summary means that bug was found on a machine that runs lto but this bug MAY or MAY NOT BE related to lto.

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 12:08:21 UTC]

Created attachment 826875 [details]
build.log

build log and emerge --info

[Comment 2 Agostino Sarubbo 2022-11-03 12:08:23 UTC]

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


FAILED: src/test/CMakeFiles/test-z3.dir/hwf.cpp.o 
/var/tmp/portage/sci-mathematics/z3-4.11.2/work/z3-z3-4.11.2/src/test/hwf.cpp:106:21: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

[Comment 3 Larry the Git Cow 2024-03-04 04:14:33 UTC]

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

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=83e5cbb7ba3a7d3973cca29465fac8b777f96cc3

commit 83e5cbb7ba3a7d3973cca29465fac8b777f96cc3
Author:     Eli Schwartz <[e-mail]>
AuthorDate: 2024-03-04 03:31:51 +0000
Commit:     Sam James <[e-mail]>
CommitDate: 2024-03-04 04:14:11 +0000

    sci-mathematics/z3: mark as LTO-unsafe, strict-aliasing unsafe
    
    The strict-aliasing violation happens only in a test program. However,
    that does mean we cannot test that z3 works when built with LTO...
    
    Closes: https://bugs.gentoo.org/879327
    Signed-off-by: Eli Schwartz <[e-mail]>
    Signed-off-by: Sam James <[e-mail]>

 sci-mathematics/z3/z3-4.12.5.ebuild | 14 +++++++++++++-
 sci-mathematics/z3/z3-4.12.6.ebuild | 14 +++++++++++++-
 2 files changed, 26 insertions(+), 2 deletions(-)

[Comment 4 Larry the Git Cow 2024-03-08 11:09:45 UTC]

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

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=64b9a3a5ab0ff976dec9025f99a183f9ad8e657f

commit 64b9a3a5ab0ff976dec9025f99a183f9ad8e657f
Author:     Eli Schwartz <[e-mail]>
AuthorDate: 2024-03-08 10:32:14 +0000
Commit:     Sam James <[e-mail]>
CommitDate: 2024-03-08 11:09:04 +0000

    sci-mathematics/z3: remove the filter-lto/fno-strict-aliasing
    
    The fix for this was featured in version 4.13.0, yay.
    
    Bug: https://bugs.gentoo.org/879327
    Signed-off-by: Eli Schwartz <[e-mail]>
    Signed-off-by: Sam James <[e-mail]>

 sci-mathematics/z3/z3-4.13.0.ebuild | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)