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Bug 859931 - media-libs/mlt-7.8.0 fails to compile (lto): factory.c:45:21: error: type of producer_count_init does not match original declaration [-Werror=lto-type-mismatch]
Summary: media-libs/mlt-7.8.0 fails to compile (lto): factory.c:45:21: error: type of ...
Status: RESOLVED FIXED
Alias: None
Product: Gentoo Linux
Classification: Unclassified
Component: Current packages (show other bugs)
Hardware: All Linux
: Normal normal (vote)
Assignee: Gentoo Media-video project
URL:
Whiteboard:
Keywords:
Depends on:
Blocks: lto
  Show dependency tree
 
Reported: 2022-07-22 06:56 UTC by Agostino Sarubbo
Modified: 2024-02-28 23:12 UTC (History)
2 users (show)

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


Attachments
build.log (build.log,161.13 KB, text/plain)
2022-07-22 06:56 UTC, Agostino Sarubbo
Details

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Description Agostino Sarubbo gentoo-dev 2022-07-22 06:56:31 UTC
https://blogs.gentoo.org/ago/2020/07/04/gentoo-tinderbox/

Issue: media-libs/mlt-7.8.0 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 2022-07-22 06:56:33 UTC
Created attachment 793019 [details]
build.log

build log and emerge --info
Comment 2 Agostino Sarubbo gentoo-dev 2022-07-22 06:56:35 UTC
Error(s) that match a know pattern in addition to what has been reported in the summary:


--   Package 'sdl2', required by 'virtual:world', not found
--   Package 'vorbis', required by 'virtual:world', not found
--   Package 'vorbisfile', required by 'virtual:world', not found
-- Could NOT find SWIG (missing: SWIG_EXECUTABLE SWIG_DIR) 
FAILED: out/lib/mlt/libmltplus.so 
/var/tmp/portage/media-libs/mlt-7.8.0/work/mlt-7.8.0/src/modules/plus/factory.c:45:21: error: type of ‘producer_count_init’ does not match original declaration [-Werror=lto-type-mismatch]
Comment 3 Agostino Sarubbo gentoo-dev 2022-07-26 09:02:32 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 4 Eli Schwartz 2024-02-28 23:06:57 UTC
This now works with mlt-7.22.0

Relevant:
https://github.com/mltframework/mlt/issues/905
https://github.com/mltframework/mlt/pull/907

(Although these fixed -Werror=odr instead, but on the other hand I suppose things changed since 7.8.0.)