Note: This is a public test instance of Red Hat Bugzilla. The data contained within is a snapshot of the live data so any changes you make will not be reflected in the production Bugzilla. Email is disabled so feel free to test any aspect of the site that you want. File any problems you find or give feedback at
Bug 1916921 - LTO Build Improvements
Summary: LTO Build Improvements
Alias: None
Product: Fedora
Classification: Fedora
Component: Changes Tracking
Version: 36
Hardware: Unspecified
OS: Unspecified
Target Milestone: ---
Assignee: Jeff Law
QA Contact:
Depends On:
Blocks: F36Changes
TreeView+ depends on / blocked
Reported: 2021-01-15 20:17 UTC by Ben Cotton
Modified: 2022-02-08 21:07 UTC (History)
7 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Last Closed: 2021-11-06 11:00:50 UTC
Type: ---

Attachments (Terms of Use)

Description Ben Cotton 2021-01-15 20:17:25 UTC
This is a tracking bug for Change: LTO Build Improvements
For more details, see:

Currently all packages that are not opted out of LTO include -ffat-lto-objects in their build flags.  This proposal would remove -ffat-lto-objects from the default LTO flags and only use it for packages that actually need it.

Comment 1 Matthew Miller 2021-04-30 20:24:58 UTC
This has landed.

Comment 2 Vít Ondruch 2021-08-12 16:06:56 UTC
(In reply to Matthew Miller from comment #1)
> This has landed.

It does not seem to be related. Are you sure you referenced the PR in the right ticket?

Comment 3 steubens 2021-08-25 06:01:53 UTC
not sure this belongs here, but renderdoc with lto broke earlier in a way that isn't noticeable without running it

unsure if -ffat-lto-objects makes it work

Comment 4 Kyle Walker 2021-10-12 19:36:49 UTC

That update was for rhbz1944428 right? I don't think this change has landed.

Comment 5 Michael J Gruber 2021-10-20 10:22:38 UTC
I'm confused about the status of this change: says it's accepted for F35, links to a FesCo ticket which accepted it for F34, and that ticket links to an unrelated devel-ml-post.

Also, the change mentions "The feature owner (Jeff Law) will need to settle on a suitable RPM macro to indicate an opt-in" and I see no such macro there. (I can change build flags myself, of course.)

The bug here references an unrelated dist-git PR.

This adds quite some confusion to a topic which can be confusing as is already for us poor little packagers who are not build chain experts.

Maybe, as a starter, document (in that change) the location of the default flags or how to check them.

Comment 6 Michael J Gruber 2021-10-20 10:32:51 UTC
OK, so by the change owner left RH and the change is not implemented.

I take it that means: We build with fat LTO everywhere and there is no special opt-in or opt-out other than adding build flags directly.

Do we have "%{_lto_cflags}" or is that a SuSE-only thing?

Comment 7 Ben Cotton 2022-02-08 21:07:43 UTC
This bug appears to have been reported against 'rawhide' during the Fedora Linux 36 development cycle.
Changing version to 36.

Note You need to log in before you can comment on or make changes to this bug.