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Bug 859307 - games-util/fteqcc-2501 fails to compile (lto): qcc_pr_comp.c:8357:96: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
Summary: games-util/fteqcc-2501 fails to compile (lto): qcc_pr_comp.c:8357:96: error: ...
Status: CONFIRMED
Alias: None
Product: Gentoo Linux
Classification: Unclassified
Component: Current packages (show other bugs)
Hardware: All Linux
: Normal normal
Assignee: Gentoo Games
URL:
Whiteboard:
Keywords:
Depends on:
Blocks: lto
  Show dependency tree
 
Reported: 2022-07-19 11:20 UTC by Agostino Sarubbo
Modified: 2024-03-20 04:18 UTC (History)
1 user (show)

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


Attachments
build.log (build.log,46.92 KB, text/plain)
2022-07-19 11:20 UTC, Agostino Sarubbo
Details

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Description Agostino Sarubbo gentoo-dev 2022-07-19 11:20:20 UTC
https://blogs.gentoo.org/ago/2020/07/04/gentoo-tinderbox/

Issue: games-util/fteqcc-2501 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 2022-07-19 11:20:22 UTC
Created attachment 792374 [details]
build.log

build log and emerge --info
Comment 2 Agostino Sarubbo gentoo-dev 2022-07-26 09:02:05 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 3 Eli Schwartz gentoo-dev 2024-03-20 04:18:41 UTC
It looks like this issue may be gone in the latest upstream version, which is 6202.

Unfortunately it seems they stopped distributing source code archives and now point source links to "latest: https://sourceforge.net/p/fteqw/code/HEAD/tree/trunk/engine/qclib"