Subject: Re: [next-20260313] kernel build fails with “ar: unrecognized option '--thin'”

From: Nicolas Schier <[email-masked]>
Date: Mon, 16 Mar 2026 13:39:47 +0100

Hi Venkat,

On Mon, Mar 16, 2026 at 03:18:50PM +0530, Venkat Rao Bagalkote wrote:
> 
> On 16/03/26 11:41 am, Venkat Rao Bagalkote wrote:
> > Greetings!!
> > 
> > 
> > I am seeing a repeatable build failure in current mainline when
> > generating vmlinux.a.
> > 
> > The build stops with an error from ar regarding the --thin option.
> > 
> > This issue is seen on IBM Power11 System.
> > 
> > Attached is the .config file.
> > 
> > Also, I see couple of build warnings, before the build fails.
> > Note: These warnings and build failure are not see on 20260312 build.
> > 
> > 
> > Warnings:
> > 
> > In file included from ./include/linux/seqlock.h:20,
> >                  from ./include/linux/mmzone.h:17,
> >                  from ./include/linux/gfp.h:7,
> >                  from ./include/linux/umh.h:4,
> >                  from ./include/linux/kmod.h:9,
> >                  from ./include/linux/module.h:18,
> >                  from drivers/char/nvram.c:34:
> > drivers/char/nvram.c:56:21: warning: ‘nvram_mutex’ defined but not used
> > [-Wunused-variable]
> >    56 | static DEFINE_MUTEX(nvram_mutex);
> >       |                     ^~~~~~~~~~~
> > ./include/linux/mutex.h:87:22: note: in definition of macro
> > ‘DEFINE_MUTEX’
> >    87 |         struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
> > 
> > 
> > Below are the failure logs.
> > 
> > 
> > ar: unrecognized option '--thin'

Thanks a lot for your report!

We missed, that 'ar --thin' is available since binutils 2.38 (released
02/2022), but Documentation/process/changes.rst still lists binutils
0.30 as build dependency.

I removed the related patch set from kbuild-for-next; we'll discuss
further at https://lore.kernel.org/linux-kbuild/[email-masked]

Kind regards,
Nicolas

> > Usage: ar [emulation options] [-]{dmpqrstx}[abcDfilMNoOPsSTuvV]
> > [--plugin <name>] [member-name] [count] archive-file file...
> >        ar -M [<mri-script]
> >  commands:
> >   d            - delete file(s) from the archive
> >   m[ab]        - move file(s) in the archive
> >   p            - print file(s) found in the archive
> >   q[f]         - quick append file(s) to the archive
> >   r[ab][f][u]  - replace existing or insert new file(s) into the archive
> >   s            - act as ranlib
> >   t[O][v]      - display contents of the archive
> >   x[o]         - extract file(s) from the archive
> >  command specific modifiers:
> >   [a]          - put file(s) after [member-name]
> >   [b]          - put file(s) before [member-name] (same as [i])
> >   [D]          - use zero for timestamps and uids/gids
> >   [U]          - use actual timestamps and uids/gids (default)
> >   [N]          - use instance [count] of name
> >   [f]          - truncate inserted file names
> >   [P]          - use full path names when matching
> >   [o]          - preserve original dates
> >   [O]          - display offsets of files in the archive
> >   [u]          - only replace files that are newer than current archive
> > contents
> >  generic modifiers:
> >   [c]          - do not warn if the library had to be created
> >   [s]          - create an archive index (cf. ranlib)
> >   [S]          - do not build a symbol table
> >   [T]          - make a thin archive
> >   [v]          - be verbose
> >   [V]          - display the version number
> >   @<file>      - read options from <file>
> >   --target=BFDNAME - specify the target object format as BFDNAME
> >   --output=DIRNAME - specify the output directory for extraction
> > operations
> >  optional:
> >   --plugin <p> - load the specified plugin
> >  emulation options:
> >   No emulation specific options
> > ar: supported targets: elf64-powerpcle elf64-powerpc elf32-powerpcle
> > elf32-powerpc aixcoff-rs6000 aixcoff64-rs6000 aix5coff64-rs6000
> > elf64-little elf64-big elf32-little elf32-big ppcboot elf32-spu
> > pe-x86-64 pei-x86-64 pe-bigobj-x86-64 elf64-x86-64 elf64-l1om elf64-k1om
> > pe-i386 pei-i386 elf32-i386 elf32-iamcu elf64-bpfle elf64-bpfbe srec
> > symbolsrec verilog tekhex binary ihex plugin
> > make[2]: *** [scripts/Makefile.vmlinux_a:22: built-in-fixup.a] Error 1
> > make[1]: *** [/root/linux-next/Makefile:1278: vmlinux_a] Error 2
> > make: *** [Makefile:248: __sub-make] Error 2
> > 
> > 
> 
> Git bisect is pointing to below commit as first bad commit.
> 
> 
> 4519221849f26a3b0c0dc45b9914a0f9cdc00740 is the first bad commit
> commit 4519221849f26a3b0c0dc45b9914a0f9cdc00740 (HEAD)
> Author: Masahiro Yamada <[email-masked]>
> Date:   Tue Oct 28 18:28:21 2025 +0000
> 
>     kbuild: move vmlinux.a build rule to scripts/Makefile.vmlinux_a
> 
>     Move the build rule for vmlinux.a to a separate file in preparation
>     for supporting distributed builds with Clang ThinLTO.
> 
>     Signed-off-by: Masahiro Yamada <[email-masked]>
>     Tested-by: Rong Xu <[email-masked]>
>     Reviewed-by: Nathan Chancellor <[email-masked]>
>     Tested-by: Nathan Chancellor <[email-masked]>
>     Link: https://patch.msgid.link/[email-masked]
>     Signed-off-by: Nicolas Schier <[email-masked]>
> 
>  Makefile                   | 16 ++++++----------
>  scripts/Makefile.vmlinux_a | 46
> ++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 52 insertions(+), 10 deletions(-)
>  create mode 100644 scripts/Makefile.vmlinux_a
> 
> 
> Git bisect log:
> 
> git bisect log
> git bisect start
> # status: waiting for both good and bad commits
> # bad: [b84a0ebe421ca56995ff78b66307667b62b3a900] Add linux-next specific
> files for 20260313
> git bisect bad b84a0ebe421ca56995ff78b66307667b62b3a900
> # status: waiting for good commit(s), bad commit known
> # good: [1f318b96cc84d7c2ab792fcc0bfd42a7ca890681] Linux 7.0-rc3
> git bisect good 1f318b96cc84d7c2ab792fcc0bfd42a7ca890681
> # bad: [ddc6cc7f66af99528c8a827d4ba835fb650b6446] Merge branch 'main' of
> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
> git bisect bad ddc6cc7f66af99528c8a827d4ba835fb650b6446
> # bad: [06da2b04b5f2f11952969e813d8dd8f0c7617b79] Merge branch 'for-next' of
> https://git.kernel.org/pub/scm/linux/kernel/git/krzk/linux.git
> git bisect bad 06da2b04b5f2f11952969e813d8dd8f0c7617b79
> # good: [85689b69dad24170252dc5be8238de2388e68871] Merge branch
> 'rust-analyzer-next' of https://github.com/Rust-for-Linux/linux.git
> git bisect good 85689b69dad24170252dc5be8238de2388e68871
> # bad: [5457bcbc73733c7268108a2acfc35c6505f3cbf3] Merge branch
> 'for-next/core' of
> https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
> git bisect bad 5457bcbc73733c7268108a2acfc35c6505f3cbf3
> # good: [5473c1ee6462a5d3543c2b4c7dc6f1aac71eb082] userfaultfd: introduce
> mfill_copy_folio_locked() helper
> git bisect good 5473c1ee6462a5d3543c2b4c7dc6f1aac71eb082
> # good: [d1b4433308592363d133a788f0443d5d63872bdd] CREDITS: simplify the
> end-of-file alphabetical order comment
> git bisect good d1b4433308592363d133a788f0443d5d63872bdd
> # good: [ff28b3bb65c3eafeece9334b908e62c492f341e5] mm/damon/core: allow
> quota goals set zero effective size quota
> git bisect good ff28b3bb65c3eafeece9334b908e62c492f341e5
> # bad: [4f6ad15007039f296611ee76dad9f6ed071e63fb] Merge branch
> 'kbuild-for-next' of
> https://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux.git
> git bisect bad 4f6ad15007039f296611ee76dad9f6ed071e63fb
> # good: [07bc816c63b94e83dbe311d84b0278e54f6b83db] Merge branch
> 'mm-unstable' of https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> git bisect good 07bc816c63b94e83dbe311d84b0278e54f6b83db
> # good: [aad94ba683adc6ff7ff4e29ae48184b42782dd97] kbuild: uapi: provide
> stub includes for some libc headers
> git bisect good aad94ba683adc6ff7ff4e29ae48184b42782dd97
> # good: [0d3fccf68d9873a3c824fb70be0dbb2c4642aa90] kbuild: Use
> '-fms-anonymous-structs' if it is available
> git bisect good 0d3fccf68d9873a3c824fb70be0dbb2c4642aa90
> # bad: [8e786d89efce381609bd7fb9e8d6c52429e8b753] kbuild: distributed build
> support for Clang ThinLTO
> git bisect bad 8e786d89efce381609bd7fb9e8d6c52429e8b753
> # bad: [4519221849f26a3b0c0dc45b9914a0f9cdc00740] kbuild: move vmlinux.a
> build rule to scripts/Makefile.vmlinux_a
> git bisect bad 4519221849f26a3b0c0dc45b9914a0f9cdc00740
> # first bad commit: [4519221849f26a3b0c0dc45b9914a0f9cdc00740] kbuild: move
> vmlinux.a build rule to scripts/Makefile.vmlinux_a
> 
> 
> Regards,
> 
> Venkat.
> 
> > 
> > If you happen to fix this issue, please add below tag.
> > 
> > 
> > Reported-by: Venkat Rao Bagalkote <[email-masked]>
> > 
> > 
> > Regards,
> > 
> > Venkat.

-- 
Nicolas