Bug 923491

Summary:	media-video/ffmpeg tc-is-lto, filter-lto, and multiple lib issues
Product:	Gentoo Linux	Reporter:	Michael Cook <mackal.cook>
Component:	Current packages	Assignee:	Gentoo Media-video project <media-video>
Status:	RESOLVED FIXED
Severity:	normal	CC:	eschwartz, floppym, mackal.cook, sam
Priority:	Normal	Keywords:	PATCH
Version:	unspecified
Hardware:	All
OS:	Linux
See Also:	https://bugs.gentoo.org/show_bug.cgi?id=772854 https://bugs.gentoo.org/show_bug.cgi?id=909572
Whiteboard:
Package list:		Runtime testing required:	---
Bug Depends on:
Bug Blocks:	618550
Attachments:	Fixed ffmpeg ebuild Min-repo ebuild demonstrating issue Min-repo ebuild eclass-debug.log diff of the changes to the ebuild

Description Michael Cook 2024-02-01 21:25:29 UTC

With multilib systems, the 2nd arch run will return false when tc-is-lto is called since filter-lto was called in the previous one.

On my system it builds x86 first, which skips LTO due to previous bugs, but still calls filter-lto which means when it gets to build amd64 tc-is-lto will return false and skip LTO.

I did check an object file with readelf -S when it should have compiled with LTO and it did not. 

I did try moving the LTO stuff to src_prepare (anything only called once before src_configure will work, but I thought it made sense to do it there)

Comment 1 Michael Cook 2024-02-01 21:27:10 UTC

Created attachment 883955 [details]
Fixed ffmpeg ebuild

This is what I ended up doing which works out fine (verified with checking object files with readelf -S)

Comment 2 Michael Cook 2024-02-01 21:37:56 UTC

Created attachment 883956 [details]
Min-repo ebuild demonstrating issue

Comment 3 Michael Cook 2024-02-01 21:39:36 UTC

Created attachment 883957 [details]
Min-repo ebuild eclass-debug.log

Comment 4 Michael Cook 2024-02-02 01:41:08 UTC

I couldn't find any other multilib packages in the tree that has this issue, but media-libs/x264 would if LTO support was added (they support LTO as a config flag) which does make me wonder if pkg_setup would be a better place to do a fix like this.

Comment 5 Eli Schwartz gentoo-dev

2024-05-26 23:57:02 UTC

Splitting the logic across multiple phases here feels kind of awkward. I sort of feel like a better approach would be to handle the LTO in a subshell, possibly a subshell for the whole src_configure.

Similar handling exists for meson.eclass, which calculates arguments including -Db_lto=true inside a subshell since commit e9189344b971f7ee0e2bec36650c57dbade4f122.

Comment 6 Michael Cook 2024-06-04 02:58:02 UTC

Created attachment 895028 [details]
diff of the changes to the ebuild

Comment 7 Larry the Git Cow gentoo-dev

2024-06-04 03:26:38 UTC

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

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=d9a701f0e4dfecb71ff54d4c8dba1a4494a2f3ea

commit d9a701f0e4dfecb71ff54d4c8dba1a4494a2f3ea
Author:     Sam James <sam@gentoo.org>
AuthorDate: 2024-06-04 03:23:30 +0000
Commit:     Sam James <sam@gentoo.org>
CommitDate: 2024-06-04 03:25:05 +0000

    media-video/ffmpeg: fix LTO handling with multilib
    
    Checking ABI and filtering based on that doesn't work in multilib_src_configure
    because of contamination & the order the phases / ABIs run in.
    
    Closes: https://bugs.gentoo.org/923491
    Thanks-to: Michael Cook <mackal.cook@gmail.com>
    Signed-off-by: Sam James <sam@gentoo.org>

 media-video/ffmpeg/ffmpeg-6.1.1-r6.ebuild | 15 ++++++++++-----
 media-video/ffmpeg/ffmpeg-9999.ebuild     | 15 ++++++++++-----
 2 files changed, 20 insertions(+), 10 deletions(-)