Bug 854534 – app-emulation/softgun-0.22 fails to compile (lto): instructions_m16c.h:163:6: error: type of [-Werror=lto-type-mismatch]

• Product: Gentoo Linux
• Status: RESOLVED FIXED

[Description Agostino Sarubbo 2022-06-27 06:20:02 UTC]

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

Issue: app-emulation/softgun-0.22 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 2022-06-27 06:20:04 UTC]

Created attachment 787892 [details]
build.log

build log and emerge --info

[Comment 2 Agostino Sarubbo 2022-07-26 09:00:18 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 Larry the Git Cow 2023-09-21 18:47:23 UTC]

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

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=b6a09b8fbe446b9c9990065fabbd07deb4ef85f3

commit b6a09b8fbe446b9c9990065fabbd07deb4ef85f3
Author:     Pascal Jäger <[e-mail]>
AuthorDate: 2023-09-21 12:05:54 +0000
Commit:     Arthur Zamarin <[e-mail]>
CommitDate: 2023-09-21 18:47:18 +0000

    app-emulation/softgun: fix build for clang16, lto
    
    revbump
    EAPI bump
    
    Closes: https://bugs.gentoo.org/854534
    Closes: https://bugs.gentoo.org/882583
    
    Signed-off-by: Pascal Jäger <[e-mail]>
    Closes: https://github.com/gentoo/gentoo/pull/32967
    Signed-off-by: Arthur Zamarin <[e-mail]>

 ....22-fix-declarations-with-type-mismatches.patch | 148 +++++++++++++++++++++
 .../files/softgun-0.22-fix-implicit-int.patch      |  33 +++++
 app-emulation/softgun/softgun-0.22-r1.ebuild       |  38 ++++++
 3 files changed, 219 insertions(+)