From: Florian Weimer <fweimer@redhat.com>
To: Richard Biener <richard.guenther@gmail.com>
Cc: gcc@gcc.gnu.org
Subject: Re: Using __gnu_lto_slim to detect -fno-fat-lto-objects
Date: Wed, 22 Feb 2023 09:28:06 +0100 [thread overview]
Message-ID: <875ybuumsp.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <CAFiYyc0fvEbNMsORRaC7U-WufSR8jRkd=776nm-Hp0CtN+=SUA@mail.gmail.com> (Richard Biener's message of "Wed, 22 Feb 2023 09:23:45 +0100")
* Richard Biener:
> On Wed, Feb 22, 2023 at 9:19 AM Florian Weimer via Gcc <gcc@gcc.gnu.org> wrote:
>>
>> Can we use the COMMON symbol __gnu_lto_slim to detect
>> -fno-fat-lto-objects on contemporary GNU/Linux (with the LTO linker
>> plugin)?
>
> Yes.
Great, thanks.
>> We currently build the distribution with -ffat-lto-objects, and I want
>> to switch away from that. Packages will need to opt in to
>> -ffat-lto-objects if static objects they build escape the buildroot.
>> And to make sure that this opt-in happens, I want to fail the build if
>> there would be any -fno-fat-lto-objects objects leaking.
>
> For SUSE we're checking that no LTO bytecode leaks instead, thus we check
> for __gnu_lto_v? (I think). The reason is that even for static libraries
> we do not want to ship LTO bytecode.
We build with -ffat-lto-objects, and this means we can create perfectly
fine object files by stripping the LTO data:
<https://src.fedoraproject.org/rpms/redhat-rpm-config/blob/rawhide/f/brp-strip-lto>
This means that so far, we only had to fix LTO compilation problems in
the packages, but not teach individual packages about LTO and non-LTO
object files. Of course it's wasteful because few packages actually
install the object files (without a final link into a program or shared
object), and that's what I want to fix.
Florian
next prev parent reply other threads:[~2023-02-22 8:28 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-22 8:18 Florian Weimer
2023-02-22 8:23 ` Richard Biener
2023-02-22 8:28 ` Florian Weimer [this message]
2023-02-22 8:58 ` Richard Biener
2023-02-23 9:53 ` Martin Liška
2023-03-02 23:57 ` Jeff Law
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=875ybuumsp.fsf@oldenburg.str.redhat.com \
--to=fweimer@redhat.com \
--cc=gcc@gcc.gnu.org \
--cc=richard.guenther@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).