[PATCH] lto.inc: add DEBUG_PREFIX_MAP back to TARGET_LDFLAGS

[PATCH] lto.inc: add DEBUG_PREFIX_MAP back to TARGET_LDFLAGS

[changqing.li]

From: Changqing Li <changqing.li@windriver.com>

DEBUG_PREFIX_MAP is appended to TARGET_LDFLAGS in commit [1] for fixing
reproducible issue when LTO is enabled. It is removed in comit [2] since
this commit causes cgo binary not reproducible. But actually, we still
need this DEBUG_PREFIX_MAP in LDFLAGS when LTO enabled. So, only appened
it when LTO is enabled. Refer [3] for the history, with this patch,
patch [4] is also needed for cgo + lto enabled.

[1] https://git.openembedded.org/openembedded-core/commit/?id=fddaecc88979967d0e00e2fafdbaaabec030da9f
[2] https://git.openembedded.org/openembedded-core/commit/?id=1797741aad02b8bf429fac4b81e30cdda64b5448
[3] https://lists.openembedded.org/g/openembedded-core/topic/patch_bitbake_conf_remove/117408334
[4] https://lists.openembedded.org/g/openembedded-core/message/230059

Signed-off-by: Changqing Li <changqing.li@windriver.com>
---
 meta/conf/distro/include/lto.inc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/meta/conf/distro/include/lto.inc b/meta/conf/distro/include/lto.inc
index 227f0c5c2a..cef92901e3 100644
--- a/meta/conf/distro/include/lto.inc
+++ b/meta/conf/distro/include/lto.inc
@@ -49,5 +49,6 @@ LTO:toolchain-clang = "${@bb.utils.contains('DISTRO_FEATURES', 'thin-lto', '-flt
 
 SELECTED_OPTIMIZATION:append = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${LTO}', '', d)}"
 TARGET_LDFLAGS:append:class-target = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${LTO}', '', d)}"
+TARGET_LDFLAGS:append:class-target = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${DEBUG_PREFIX_MAP}', '', d)}"
 
 SELECTED_OPTIMIZATION[vardeps] += "LTO LTOEXTRA"
-- 
2.34.1

Re: [PATCH] lto.inc: add DEBUG_PREFIX_MAP back to TARGET_LDFLAGS

[Richard Purdie]

On Wed, 2026-02-04 at 13:26 +0800, changqing.li@windriver.com wrote:
> From: Changqing Li <changqing.li@windriver.com>
> 
> DEBUG_PREFIX_MAP is appended to TARGET_LDFLAGS in commit [1] for fixing
> reproducible issue when LTO is enabled. It is removed in comit [2] since
> this commit causes cgo binary not reproducible. But actually, we still
> need this DEBUG_PREFIX_MAP in LDFLAGS when LTO enabled. So, only appened
> it when LTO is enabled. Refer [3] for the history, with this patch,
> patch [4] is also needed for cgo + lto enabled.
> 
> [1] https://git.openembedded.org/openembedded-core/commit/?id=fddaecc88979967d0e00e2fafdbaaabec030da9f
> [2] https://git.openembedded.org/openembedded-core/commit/?id=1797741aad02b8bf429fac4b81e30cdda64b5448
> [3] https://lists.openembedded.org/g/openembedded-core/topic/patch_bitbake_conf_remove/117408334
> [4] https://lists.openembedded.org/g/openembedded-core/message/230059
> 
> Signed-off-by: Changqing Li <changqing.li@windriver.com>
> ---
>  meta/conf/distro/include/lto.inc | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/meta/conf/distro/include/lto.inc b/meta/conf/distro/include/lto.inc
> index 227f0c5c2a..cef92901e3 100644
> --- a/meta/conf/distro/include/lto.inc
> +++ b/meta/conf/distro/include/lto.inc
> @@ -49,5 +49,6 @@ LTO:toolchain-clang = "${@bb.utils.contains('DISTRO_FEATURES', 'thin-lto', '-flt
>  
>  SELECTED_OPTIMIZATION:append = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${LTO}', '', d)}"
>  TARGET_LDFLAGS:append:class-target = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${LTO}', '', d)}"
> +TARGET_LDFLAGS:append:class-target = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${DEBUG_PREFIX_MAP}', '', d)}"
>  
>  SELECTED_OPTIMIZATION[vardeps] += "LTO LTOEXTRA"

We need a bit more information. Which version of gcc did you see this issue with?

gcc see this as a bug, for example they added this to fix it:

https://gcc.gnu.org/cgit/gcc/commit/?id=7cc2df084b7977653a9b59cbc34a9ad500ae619c

In:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101473#c21

"I think it is a bug - -fdebug-prefix-map should be fully reflected in
the LTO IL and thus we should not end up creating un-remapped
references to files (we should not create many references to files late
anyway)."

i.e. it is a bug if we have to set this in LDFLAGS if I understand
correctly. So we should file a bug with gcc about this, assuming you
were using gcc 12 or later.

Cheers,

Richard

Re: [PATCH] lto.inc: add DEBUG_PREFIX_MAP back to TARGET_LDFLAGS

[Ricardo de Araujo (Salveti)]

On Wed, Feb 4, 2026 at 2:26 AM <changqing.li@windriver.com> wrote:
>
> From: Changqing Li <changqing.li@windriver.com>
>
> DEBUG_PREFIX_MAP is appended to TARGET_LDFLAGS in commit [1] for fixing
> reproducible issue when LTO is enabled. It is removed in comit [2] since
> this commit causes cgo binary not reproducible. But actually, we still
> need this DEBUG_PREFIX_MAP in LDFLAGS when LTO enabled. So, only appened
> it when LTO is enabled. Refer [3] for the history, with this patch,
> patch [4] is also needed for cgo + lto enabled.
>
> [1] https://git.openembedded.org/openembedded-core/commit/?id=fddaecc88979967d0e00e2fafdbaaabec030da9f
> [2] https://git.openembedded.org/openembedded-core/commit/?id=1797741aad02b8bf429fac4b81e30cdda64b5448
> [3] https://lists.openembedded.org/g/openembedded-core/topic/patch_bitbake_conf_remove/117408334
> [4] https://lists.openembedded.org/g/openembedded-core/message/230059
>
> Signed-off-by: Changqing Li <changqing.li@windriver.com>
> ---
>  meta/conf/distro/include/lto.inc | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/meta/conf/distro/include/lto.inc b/meta/conf/distro/include/lto.inc
> index 227f0c5c2a..cef92901e3 100644
> --- a/meta/conf/distro/include/lto.inc
> +++ b/meta/conf/distro/include/lto.inc
> @@ -49,5 +49,6 @@ LTO:toolchain-clang = "${@bb.utils.contains('DISTRO_FEATURES', 'thin-lto', '-flt
>
>  SELECTED_OPTIMIZATION:append = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${LTO}', '', d)}"
>  TARGET_LDFLAGS:append:class-target = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${LTO}', '', d)}"
> +TARGET_LDFLAGS:append:class-target = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${DEBUG_PREFIX_MAP}', '', d)}"
>
>  SELECTED_OPTIMIZATION[vardeps] += "LTO LTOEXTRA"

As raised by Randolph in the previous thread
(https://lists.openembedded.org/g/openembedded-core/message/230469),
this will only fix the build for users that are enabling LTO in OE,
but we still have quite a few recipes enabling LTO as part of the
project meson/make/etc files (e.g. lxc) even when lto.inc is not used.

Thanks,

Ricardo

Re: [PATCH] lto.inc: add DEBUG_PREFIX_MAP back to TARGET_LDFLAGS

[Richard Purdie]

On Wed, 2026-02-04 at 15:17 -0300, Ricardo de Araujo (Salveti) wrote:
> On Wed, Feb 4, 2026 at 2:26 AM <changqing.li@windriver.com> wrote:
> > 
> > From: Changqing Li <changqing.li@windriver.com>
> > 
> > DEBUG_PREFIX_MAP is appended to TARGET_LDFLAGS in commit [1] for fixing
> > reproducible issue when LTO is enabled. It is removed in comit [2] since
> > this commit causes cgo binary not reproducible. But actually, we still
> > need this DEBUG_PREFIX_MAP in LDFLAGS when LTO enabled. So, only appened
> > it when LTO is enabled. Refer [3] for the history, with this patch,
> > patch [4] is also needed for cgo + lto enabled.
> > 
> > [1] https://git.openembedded.org/openembedded-core/commit/?id=fddaecc88979967d0e00e2fafdbaaabec030da9f
> > [2] https://git.openembedded.org/openembedded-core/commit/?id=1797741aad02b8bf429fac4b81e30cdda64b5448
> > [3] https://lists.openembedded.org/g/openembedded-core/topic/patch_bitbake_conf_remove/117408334
> > [4] https://lists.openembedded.org/g/openembedded-core/message/230059
> > 
> > Signed-off-by: Changqing Li <changqing.li@windriver.com>
> > ---
> >  meta/conf/distro/include/lto.inc | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/meta/conf/distro/include/lto.inc b/meta/conf/distro/include/lto.inc
> > index 227f0c5c2a..cef92901e3 100644
> > --- a/meta/conf/distro/include/lto.inc
> > +++ b/meta/conf/distro/include/lto.inc
> > @@ -49,5 +49,6 @@ LTO:toolchain-clang = "${@bb.utils.contains('DISTRO_FEATURES', 'thin-lto', '-flt
> > 
> >  SELECTED_OPTIMIZATION:append = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${LTO}', '', d)}"
> >  TARGET_LDFLAGS:append:class-target = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${LTO}', '', d)}"
> > +TARGET_LDFLAGS:append:class-target = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${DEBUG_PREFIX_MAP}', '', d)}"
> > 
> >  SELECTED_OPTIMIZATION[vardeps] += "LTO LTOEXTRA"
> 
> As raised by Randolph in the previous thread
> (https://lists.openembedded.org/g/openembedded-core/message/230469),
> this will only fix the build for users that are enabling LTO in OE,
> but we still have quite a few recipes enabling LTO as part of the
> project meson/make/etc files (e.g. lxc) even when lto.inc is not used.

See my other reply. According to the bug report links where this was
discussed, upstream think this is a bug in gcc/binutils itself and you
shouldn't have to pass these options to the linker.

I think we do need to narrow down a test case for upstream and see if
this really is a bug or not.

It may be we have to work around this in recipes that are forcing LTO
unconditionally, I'd hope there aren't that many of them? Perhaps just
force the include for those recipes?

Cheers,

Richard

Re: [OE-core] [PATCH] lto.inc: add DEBUG_PREFIX_MAP back to TARGET_LDFLAGS

[Jörg Sommer]

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Changqing Li via lists.openembedded.org schrieb am Mi 04. Feb, 13:26 (+0800):
> From: Changqing Li <changqing.li@windriver.com>
> 
> DEBUG_PREFIX_MAP is appended to TARGET_LDFLAGS in commit [1] for fixing
> reproducible issue when LTO is enabled. It is removed in comit [2] since
> this commit causes cgo binary not reproducible. But actually, we still
> need this DEBUG_PREFIX_MAP in LDFLAGS when LTO enabled. So, only appened
> it when LTO is enabled. Refer [3] for the history, with this patch,
> patch [4] is also needed for cgo + lto enabled.

Gentle ping. This patch is missing, otherwise QA check buildpaths matches in
nearly all packages.

But this still leaves some packages with buildpaths, because there's a bug
in gcc that it does not apply -ffile-prefix-map:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124581

> diff --git a/meta/conf/distro/include/lto.inc b/meta/conf/distro/include/lto.inc
> index 227f0c5c2a..cef92901e3 100644
> --- a/meta/conf/distro/include/lto.inc
> +++ b/meta/conf/distro/include/lto.inc
> @@ -49,5 +49,6 @@ LTO:toolchain-clang = "${@bb.utils.contains('DISTRO_FEATURES', 'thin-lto', '-flt
>  
>  SELECTED_OPTIMIZATION:append = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${LTO}', '', d)}"
>  TARGET_LDFLAGS:append:class-target = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${LTO}', '', d)}"
> +TARGET_LDFLAGS:append:class-target = "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${DEBUG_PREFIX_MAP}', '', d)}"

Possibly, I would join these lines.


Best regards Jörg

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Re: [OE-core] [PATCH] lto.inc: add DEBUG_PREFIX_MAP back to TARGET_LDFLAGS

[Thomas Perrot]

[-- Attachment #1: Type: text/plain, Size: 1991 bytes --]

   1. Hello,
      
On Sat, 2026-03-28 at 21:26 +0100, Jörg Sommer via
lists.openembedded.org wrote:
> Changqing Li via lists.openembedded.org schrieb am Mi 04. Feb, 13:26
> (+0800):
> > From: Changqing Li <changqing.li@windriver.com>
> > 
> > DEBUG_PREFIX_MAP is appended to TARGET_LDFLAGS in commit [1] for
> > fixing
> > reproducible issue when LTO is enabled. It is removed in comit [2]
> > since
> > this commit causes cgo binary not reproducible. But actually, we
> > still
> > need this DEBUG_PREFIX_MAP in LDFLAGS when LTO enabled. So, only
> > appened
> > it when LTO is enabled. Refer [3] for the history, with this patch,
> > patch [4] is also needed for cgo + lto enabled.
> 
> Gentle ping. This patch is missing, otherwise QA check buildpaths
> matches in
> nearly all packages.

I confirm this patch is required to fix QA check build paths for a few
packages. 
Kind regards,
Thomas Perrot

> 
> But this still leaves some packages with buildpaths, because there's
> a bug
> in gcc that it does not apply -ffile-prefix-map:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124581
> 
> > diff --git a/meta/conf/distro/include/lto.inc
> > b/meta/conf/distro/include/lto.inc
> > index 227f0c5c2a..cef92901e3 100644
> > --- a/meta/conf/distro/include/lto.inc
> > +++ b/meta/conf/distro/include/lto.inc
> > @@ -49,5 +49,6 @@ LTO:toolchain-clang =
> > "${@bb.utils.contains('DISTRO_FEATURES', 'thin-lto', '-flt
> >  
> >  SELECTED_OPTIMIZATION:append =
> > "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${LTO}', '', d)}"
> >  TARGET_LDFLAGS:append:class-target =
> > "${@bb.utils.contains('DISTRO_FEATURES', 'lto', ' ${LTO}', '', d)}"
> > +TARGET_LDFLAGS:append:class-target =
> > "${@bb.utils.contains('DISTRO_FEATURES', 'lto', '
> > ${DEBUG_PREFIX_MAP}', '', d)}"
> 
> Possibly, I would join these lines.
> 
> 
> Best regards Jörg

-- 
Thomas Perrot, Bootlin Embedded Linux and kernel engineering
https://bootlin.com

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Re: [OE-core] [PATCH] lto.inc: add DEBUG_PREFIX_MAP back to TARGET_LDFLAGS

[Richard Purdie]

On Mon, 2026-03-30 at 11:59 +0200, Thomas Perrot wrote:
>    1. Hello,
>       
> On Sat, 2026-03-28 at 21:26 +0100, Jörg Sommer via
> lists.openembedded.org wrote:
> > Changqing Li via lists.openembedded.org schrieb am Mi 04. Feb,
> > 13:26
> > (+0800):
> > > From: Changqing Li <changqing.li@windriver.com>
> > > 
> > > DEBUG_PREFIX_MAP is appended to TARGET_LDFLAGS in commit [1] for
> > > fixing
> > > reproducible issue when LTO is enabled. It is removed in comit
> > > [2]
> > > since
> > > this commit causes cgo binary not reproducible. But actually, we
> > > still
> > > need this DEBUG_PREFIX_MAP in LDFLAGS when LTO enabled. So, only
> > > appened
> > > it when LTO is enabled. Refer [3] for the history, with this
> > > patch,
> > > patch [4] is also needed for cgo + lto enabled.
> > 
> > Gentle ping. This patch is missing, otherwise QA check buildpaths
> > matches in
> > nearly all packages.
> 
> I confirm this patch is required to fix QA check build paths for a
> few packages. 

Can someone please work out a smaller reproducer to provide to upstream
gcc/binutils so we can try and get the underlying bug fixed?

Thanks,

Richard

Re: [OE-core] [PATCH] lto.inc: add DEBUG_PREFIX_MAP back to TARGET_LDFLAGS

[Jörg Sommer]

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Richard Purdie schrieb am Mo 30. Mär, 11:18 (+0100):
> On Mon, 2026-03-30 at 11:59 +0200, Thomas Perrot wrote:
> >    1. Hello,
> >       
> > On Sat, 2026-03-28 at 21:26 +0100, Jörg Sommer via
> > lists.openembedded.org wrote:
> > > Changqing Li via lists.openembedded.org schrieb am Mi 04. Feb,
> > > 13:26
> > > (+0800):
> > > > From: Changqing Li <changqing.li@windriver.com>
> > > > 
> > > > DEBUG_PREFIX_MAP is appended to TARGET_LDFLAGS in commit [1] for
> > > > fixing
> > > > reproducible issue when LTO is enabled. It is removed in comit
> > > > [2]
> > > > since
> > > > this commit causes cgo binary not reproducible. But actually, we
> > > > still
> > > > need this DEBUG_PREFIX_MAP in LDFLAGS when LTO enabled. So, only
> > > > appened
> > > > it when LTO is enabled. Refer [3] for the history, with this
> > > > patch,
> > > > patch [4] is also needed for cgo + lto enabled.
> > > 
> > > Gentle ping. This patch is missing, otherwise QA check buildpaths
> > > matches in
> > > nearly all packages.
> > 
> > I confirm this patch is required to fix QA check build paths for a
> > few packages. 
> 
> Can someone please work out a smaller reproducer to provide to upstream
> gcc/binutils so we can try and get the underlying bug fixed?

I've send some simple test cases in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124581


Best regards Jörg

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Tatzendpromenade 2       F: 03641 - 526 306
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Re: [OE-core] [PATCH] lto.inc: add DEBUG_PREFIX_MAP back to TARGET_LDFLAGS

[Richard Purdie]

On Mon, 2026-03-30 at 12:23 +0200, Jörg Sommer wrote:
> Richard Purdie schrieb am Mo 30. Mär, 11:18 (+0100):
> > On Mon, 2026-03-30 at 11:59 +0200, Thomas Perrot wrote:
> > > On Sat, 2026-03-28 at 21:26 +0100, Jörg Sommer via
> > > lists.openembedded.org wrote:
> > > > Changqing Li via lists.openembedded.org schrieb am Mi 04. Feb,
> > > 
> > > I confirm this patch is required to fix QA check build paths for a
> > > few packages. 
> > 
> > Can someone please work out a smaller reproducer to provide to upstream
> > gcc/binutils so we can try and get the underlying bug fixed?
> 
> I've send some simple test cases in
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124581

Thanks, I've tried to raise awareness in the other bug.

Cheers,

Richard