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Bug 859607 - media-gfx/blender-2.93.9 fails to compile (lto): DNA_image_types.h:135:16: error: type struct Image violates the C++ One Definition Rule [-Werror=odr]
Summary: media-gfx/blender-2.93.9 fails to compile (lto): DNA_image_types.h:135:16: er...
Status: CONFIRMED
Alias: None
Product: Gentoo Linux
Classification: Unclassified
Component: Current packages (show other bugs)
Hardware: All Linux
: Normal normal (vote)
Assignee: Adrian
URL:
Whiteboard:
Keywords:
Depends on:
Blocks: lto
  Show dependency tree
 
Reported: 2022-07-21 06:50 UTC by Agostino Sarubbo
Modified: 2022-07-26 09:02 UTC (History)
2 users (show)

See Also:
Package list:
Runtime testing required: ---


Attachments
build.log.xz (build.log.xz,221.65 KB, application/x-xz)
2022-07-21 06:50 UTC, Agostino Sarubbo
Details

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Description Agostino Sarubbo gentoo-dev 2022-07-21 06:50:30 UTC
https://blogs.gentoo.org/ago/2020/07/04/gentoo-tinderbox/

Issue: media-gfx/blender-2.93.9 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 gentoo-dev 2022-07-21 06:50:35 UTC
Created attachment 792689 [details]
build.log.xz

build log and emerge --info (compressed because it exceeds attachment limit, use 'xzless' to read it)
Comment 2 Agostino Sarubbo gentoo-dev 2022-07-21 06:50:38 UTC
Error(s) that match a know pattern in addition to what has been reported in the summary:


-- Could NOT find Clang (missing: _CLANG_LIBRARIES CLANG_INCLUDE_DIR) 
FAILED: bin/blender 
/var/tmp/portage/media-gfx/blender-2.93.9/work/blender-2.93.9/source/blender/makesdna/DNA_image_types.h:135:16: error: type ‘struct Image’ violates the C++ One Definition Rule [-Werror=odr]
Comment 3 Sebastian Parborg 2022-07-21 16:02:15 UTC
I'm guessing the `-Werror` defines are because these warning will cause issue when doing link time optimization?

If that is the case, this seems to be an issue for upstream and not the ebuild itself?
Comment 4 Agostino Sarubbo gentoo-dev 2022-07-26 09:02:12 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