Bug 858374 – dev-util/glslang-1.3.224-r1 fails to compile (lto): GlslangToSpv.cpp:1341:33: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

• Status: RESOLVED FIXED
• Product: Gentoo Linux

[Description Agostino Sarubbo 2022-07-16 15:39:28 UTC]

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

Issue: dev-util/glslang-1.3.216 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 2022-07-16 15:39:31 UTC]

Created attachment 791735 [details]
build.log

build log and emerge --info

[Comment 2 Agostino Sarubbo 2022-07-16 15:39:33 UTC]

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


FAILED: SPIRV/CMakeFiles/SPIRV.dir/GlslangToSpv.cpp.o 
/var/tmp/portage/dev-util/glslang-1.3.216/work/glslang-sdk-1.3.216.0/SPIRV/GlslangToSpv.cpp:1341:33: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

[Comment 3 Nick Sarnie 2022-07-16 19:45:49 UTC]

Would you be willing to report this upstream? I can't imagine it's a packaging bug.

[Comment 4 Agostino Sarubbo 2022-07-26 09:01:28 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 5 Agostino Sarubbo 2022-09-26 08:32:18 UTC]

lto_tinderbox has reproduced this issue with version 1.3.224-r1 - Updating summary.

[Comment 6 Jocelyn Mayer 2022-12-22 12:42:04 UTC]

For information, after a few tests, glslang-1.3.231-r2 seems to build fine without any patch / CFLAGS modification.

[Comment 7 Nick Sarnie 2024-01-19 03:10:59 UTC]

Is this still reproducible?

[Comment 8 Eli Schwartz 2024-03-04 06:06:04 UTC]

Right, this appears to have been fixed upstream.