Bug 864529

Summary:	x11-libs/libdrm-2.4.112 fails to compile (lto): test_decode.c:109:39: error: dereferencing type-punned pointer might break strict-aliasing rules [-Werror=strict-aliasing]
Product:	Gentoo Linux	Reporter:	Agostino Sarubbo <ago>
Component:	Current packages	Assignee:	Gentoo X packagers <x11>
Status:	RESOLVED FIXED
Severity:	normal
Priority:	Normal
Version:	unspecified
Hardware:	All
OS:	Linux
URL:	https://gitlab.freedesktop.org/mesa/drm/-/merge_requests/258
Whiteboard:
Package list:		Runtime testing required:	---
Bug Depends on:
Bug Blocks:	618550
Attachments:	build.log

Description Agostino Sarubbo gentoo-dev

2022-08-09 07:07:59 UTC

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

Issue: x11-libs/libdrm-2.4.112 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 gentoo-dev

2022-08-09 07:08:01 UTC

Created attachment 798953 [details]
build.log

build log and emerge --info

Comment 2 Agostino Sarubbo gentoo-dev

2022-08-09 07:08:03 UTC

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


FAILED: intel/test_decode.p/test_decode.c.o 
Run-time dependency cunit found: NO (tried pkgconfig and cmake)
../libdrm-2.4.112/intel/test_decode.c:109:39: error: dereferencing type-punned pointer might break strict-aliasing rules [-Werror=strict-aliasing]

Comment 3 Larry the Git Cow gentoo-dev

2022-08-31 14:48:53 UTC

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

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=c87497c4f1b0a461426af9e5a6465c1493f39fb9

commit c87497c4f1b0a461426af9e5a6465c1493f39fb9
Author:     Matt Turner <mattst88@gentoo.org>
AuthorDate: 2022-08-31 14:42:31 +0000
Commit:     Matt Turner <mattst88@gentoo.org>
CommitDate: 2022-08-31 14:48:29 +0000

    x11-libs/libdrm: Version bump to 2.4.113
    
    Closes: https://bugs.gentoo.org/864529
    Signed-off-by: Matt Turner <mattst88@gentoo.org>

 x11-libs/libdrm/Manifest              |  1 +
 x11-libs/libdrm/libdrm-2.4.113.ebuild | 66 +++++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+)