On Wed, 2021-08-04 at 20:13 -0400, Randy MacLeod wrote:
> On 2021-07-27 9:34 a.m., Tony Battersby wrote:
> > Currently, enabling Link Time Optimization via:
> >
> > require conf/distro/include/lto.inc
> > DISTRO_FEATURES_append = " lto"
> >
> > makes the build non-reproducible (as in
> > https://reproducible-builds.org/). This patch set fixes some of the
> > problems, but is not yet a complete solution.
> >
> > This patch set addresses the following bugs:
> > https://bugzilla.yoctoproject.org/show_bug.cgi?id=14481
> > https://bugzilla.yoctoproject.org/show_bug.cgi?id=14490
> >
> > openembedded-core patches
> > 1/4: lto.inc: disable LTO for grub
> > 2/4: gcc: Backport patch to make LTO builds more reproducible
> > 3/4: bitbake.conf: add DEBUG_PREFIX_MAP to TARGET_LDFLAGS
> >
> > openembedded-devel patches
> > 4/4: net-snmp: fix QA Issue after LDFLAGS change
> >
> > Patch 3 adds DEBUG_PREFIX_MAP to TARGET_LDFLAGS (it was already in
> > TARGET_CFLAGS). This could possibly be done differently, such as by
> > removing it from TARGET_CFLAGS and adding it to TOOLCHAIN_OPTIONS,
> > TARGET_CC_ARCH, or TUNE_CCARGS, but I haven't tested those. Let me know
> > if there is a better/preferred way to do it.
> >
> > The TARGET_LDFLAGS change broke net-snmp from meta-networking, so I have
> > included a patch to fix that. Other packages might have been broken as
> > well, although I haven't found any others.
> >
> > With all these patches, there are still many shared libraries in /lib
> > and /usr/lib that are still not reproducible with LTO enabled because
> > x86_64-poky-linux-libtool filters out the -f*-prefix-map flags added by
> > patch 3 when linking shared libraries. /usr/lib/libbz2.so.1.0.6 from
> > the libbz2 package from the bzip2 recipe is a good example. I do not
> > have a patch for that problem. I will leave that to someone else.
> >
> > So this is what we need to achieve reproducible LTO builds:
> > *) This patch set
> > *) A fix for libtool
> > *) Add LTO to reproducible builds testing if appropriate (e.g.
> > meta/lib/oeqa/selftest/cases/reproducible.py, CI on Autobuilder)
> > *) Fixes for individual packages, if needed
> > *) Once everything works, update the documentation again (I previously
> > requested a documentation change for this bug, which will eventually
> > show up at
> > http://docs.yoctoproject.org/test-manual/reproducible-builds.html).
>
> This is certainly a few steps in the right direction with a good outline
> of what's next.
>
> I suspect that Richard has been busy with other things like overrides
> and the update to glibc-2.34.
>
> Do you have any suggestions or questions about what we should do
> with this patch series Richard?
Thanks for the reminder, I've been meaning to queue/test this which I will
do. The gcc version has been bumped but I ported the patch forward to it
and the patches are in master-next for testing. It is great to see this
support moving forward.
Much as it pains me to admit having any libtool knowledge, I may be able to
help with that bit. There is an untested patch below which may address that
issue, or at least give a good hint on how to do it if it doesn't work. I
don't have an environment to test easily right now.
Cheers,
Richard
>From 7681b0a1461f22034e1f70328a060db34474c60f Mon Sep 17 00:00:00 2001
From: Richard Purdie <richard.pur...@linuxfoundation.org>
Date: Thu, 5 Aug 2021 11:18:20 +0100
Subject: libtool: Fix lto option passing?
Signed-off-by: Richard Purdie <richard.pur...@linuxfoundation.org>
---
meta/recipes-devtools/libtool/libtool-2.4.6.inc | 1 +
meta/recipes-devtools/libtool/libtool/lto-prefix.patch | 16 ++++++++++++++++
2 files changed, 17 insertions(+)
create mode 100644 meta/recipes-devtools/libtool/libtool/lto-prefix.patch
diff --git a/meta/recipes-devtools/libtool/libtool-2.4.6.inc
b/meta/recipes-devtools/libtool/libtool-2.4.6.inc
index c1cbceb51f..6748d7468e 100644
--- a/meta/recipes-devtools/libtool/libtool-2.4.6.inc
+++ b/meta/recipes-devtools/libtool/libtool-2.4.6.inc
@@ -23,6 +23,7 @@ SRC_URI = "${GNU_MIRROR}/libtool/libtool-${PV}.tar.gz \
file://0001-libtool-Check-for-static-libs-for-internal-compiler-.patch \
file://0001-Makefile.am-make-sure-autoheader-run-before-autoconf.patch \
file://0001-Makefile.am-make-sure-autoheader-run-before-automake.patch \
+ file://lto-prefix.patch \
"
SRC_URI[md5sum] = "addf44b646ddb4e3919805aa88fa7c5e"
diff --git a/meta/recipes-devtools/libtool/libtool/lto-prefix.patch
b/meta/recipes-
devtools/libtool/libtool/lto-prefix.patch
new file mode 100644
index 0000000000..f788b3fc27
--- /dev/null
+++ b/meta/recipes-devtools/libtool/libtool/lto-prefix.patch
@@ -0,0 +1,16 @@
+Index: libtool-2.4.6/build-aux/ltmain.in
+===================================================================
+--- libtool-2.4.6.orig/build-aux/ltmain.in
++++ libtool-2.4.6/build-aux/ltmain.in
+@@ -5424,9 +5424,10 @@ func_mode_link ()
+ # --sysroot=* for sysroot support
+ # -O*, -g*, -flto*, -fwhopr*, -fuse-linker-plugin GCC link-time
optimization
+ # -stdlib=* select c++ std lib with clang
++ # -f*-prefix-map* needed for lto linking
+ -64|-mips[0-9]|-r[0-9][0-9]*|-xarch=*|-xtarget=*|+DA*|+DD*|-q*|-m*| \
+
-t[45]*|-txscale*|-p|-pg|--coverage|-fprofile-*|-F*|@*|-tp=*|--sysroot=*| \
+-
-O*|-g*|-flto*|-fwhopr*|-fuse-linker-plugin|-fstack-protector*|-stdlib=*)
++
-O*|-g*|-flto*|-fwhopr*|-fuse-linker-plugin|-fstack-protector*|-stdlib=*|-f*-prefix-map*)
+ func_quote_for_eval "$arg"
+ arg=$func_quote_for_eval_result
+ func_append compile_command " $arg"
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