wip! mold: fatal: failed to load plugin : /usr/bin/ld: undefined symbol: onload

[okias]

I need to test against default linker in CI, if this will happen too, but so far it could be on mold side, so dropping here as WIP report-in-progress.
Ref: https://gitlab.freedesktop.org/dh/mesa/-/jobs/65017251 .

FAILED: src/nouveau/compiler/nak 
rustc -C linker=compiler-wrapper-clang-15.sh --color=always -C debug-assertions=no -C overflow-checks=no --crate-type bin -D warnings --edition=2021 -C opt-level=3 --crate-name nak --emit dep-info=src/nouveau/compiler/nak.d --emit link=src/nouveau/compiler/nak --out-dir src/nouveau/compiler/nak.p -C metadata=ed48680@@nak@exe -Aclippy::identity_op -Aclippy::len_zero -Aclippy::manual_range_contains -Aclippy::needless_range_loop -Aclippy::redundant_field_names -Aclippy::upper_case_acronyms -Aclippy::vec_box -Aclippy::write_with_newline -Aclippy::not_unsafe_ptr_arg_deref -Anon_snake_case -Clink-arg=-Wno-unused-command-line-argument -C default-linker-libraries --test --extern bitview=src/nouveau/compiler/libbitview.rlib --extern nak_bindings=src/nouveau/compiler/libnak_bindings.rlib --extern compiler=src/compiler/rust/libcompiler.rlib --extern nak_ir_proc=src/nouveau/compiler/libnak_ir_proc.so --extern acorn=src/nouveau/compiler/libacorn.rlib --extern paste=subprojects/paste-1.0.14/libpaste.so --extern nvidia_headers=src/nouveau/headers/libnvidia_headers.rlib -Clink-arg=src/nouveau/winsys/libnouveau_ws.a -Clink-arg=src/nouveau/headers/libnvidia_headers_c.a -Clink-arg=src/compiler/libcompiler.a -Clink-arg=src/util/libmesa_util.a -Clink-arg=src/util/libmesa_util_sse41.a -Clink-arg=src/util/blake3/libblake3.a -Clink-arg=src/c11/impl/libmesa_util_c11.a --extern nv_push_rs=src/nouveau/headers/libnv_push_rs.rlib -Clink-arg=/usr/lib/x86_64-linux-gnu/libdrm.so -Clink-arg=/usr/lib/x86_64-linux-gnu/libz.so -Clink-arg=-pthread -Clink-arg=/lib/x86_64-linux-gnu/libzstd.so -Clink-arg=/usr/lib/x86_64-linux-gnu/libunwind.so -Clink-arg=-pthread -Clink-arg=-pthread -Lsrc/nouveau/compiler -Lsrc/compiler/rust -Lsubprojects/paste-1.0.14 -Lsrc/nouveau/headers -Lsrc/nouveau/winsys -Lsrc/compiler -Lsrc/util -Lsrc/util/blake3 -Lsrc/c11/impl -Clink-arg=-L/usr/lib/llvm-15/lib/clang/15.0.6 -Clink-arg=-L/usr/bin/../lib/gcc/x86_64-linux-gnu/12 -Clink-arg=-L/usr/lib/gcc/x86_64-linux-gnu/12 -Clink-arg=-L/usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../lib64 -Clink-arg=-L/usr/lib64 -Clink-arg=-L/lib/x86_64-linux-gnu -Clink-arg=-L/usr/lib/x86_64-linux-gnu -Clink-arg=-L/lib/../lib64 -Clink-arg=-L/usr/lib/../lib64 -Clink-arg=-L/lib -Clink-arg=-L/usr/lib -Clink-arg=-lstdc++ -C 'link-arg=-Wl,-rpath,$ORIGIN/:$ORIGIN/../../../subprojects/paste-1.0.14:/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib' -C link-arg=-Wl,-rpath-link,/builds/dh/mesa/_build/src/nouveau/compiler:/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib -C link-arg=-Wl,-rpath-link,/builds/dh/mesa/_build/subprojects/paste-1.0.14:/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib ../src/nouveau/compiler/nak/lib.rs
error: linking with `compiler-wrapper-clang-15.sh` failed: exit status: 1
  |
  = note: LC_ALL="C" PATH="/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin:/root/.cargo/bin:/usr/lib/ccache:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/builds/dh/mesa/.gitlab-ci/build" VSLANG="1033" "compiler-wrapper-clang-15.sh" "-m64" "/tmp/rustcEarXEa/symbols.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.00.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.01.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.02.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.03.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.04.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.05.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.06.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.07.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.08.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.09.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.10.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.11.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.12.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.13.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.14.rcgu.o" "src/nouveau/compiler/nak.p/nak.nak.c6ffe18af4df074d-cgu.15.rcgu.o" "src/nouveau/compiler/nak.p/nak.4tzxoe3qr35rwygh.rcgu.o" "-Wl,--as-needed" "-L" "src/nouveau/compiler" "-L" "src/compiler/rust" "-L" "subprojects/paste-1.0.14" "-L" "src/nouveau/headers" "-L" "src/nouveau/winsys" "-L" "src/compiler" "-L" "src/util" "-L" "src/util/blake3" "-L" "src/c11/impl" "-L" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-Wl,-Bstatic" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libtest-5d722ce3e5d0595e.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libgetopts-76f5006e4e062e57.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libunicode_width-a18ed5fdf4a57b72.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_std_workspace_std-a14b8d31733ef9e9.rlib" "/builds/dh/mesa/_build/src/nouveau/headers/libnv_push_rs.rlib" "/builds/dh/mesa/_build/src/nouveau/compiler/libacorn.rlib" "/builds/dh/mesa/_build/src/nouveau/compiler/libnak_bindings.rlib" "/builds/dh/mesa/_build/src/compiler/rust/libcompiler.rlib" "/builds/dh/mesa/_build/src/nouveau/headers/libnvidia_headers.rlib" "/builds/dh/mesa/_build/src/nouveau/compiler/libbitview.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd-66d8041607d2929b.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libpanic_unwind-a57e2388c0aea9b1.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libobject-dcd9be90ae2cb505.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libmemchr-516789932d161b4e.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libaddr2line-1ff34b0cf871cb60.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libgimli-0c110dd0650d6cb7.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_demangle-a6e97aae2681ad8f.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd_detect-b93dac2525ec4d1e.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libhashbrown-ce1d65fb391ae98b.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_std_workspace_alloc-8933a2fb54d88492.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libminiz_oxide-306712ebb1ee1a3f.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libadler-349c574f342b0d30.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libunwind-65c422a3ad95273d.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcfg_if-7e6330a6c0cb9441.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/liblibc-39c59240bfdfab27.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/liballoc-e9d126c51bb8b2bb.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_std_workspace_core-5af394d9b1f07bdc.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-693a8f23970c5917.rlib" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-13fc9d1ed9c7a2bc.rlib" "-Wl,-Bdynamic" "-lgcc_s" "-lutil" "-lrt" "-lpthread" "-lm" "-ldl" "-lc" "-Wl,--eh-frame-hdr" "-Wl,-z,noexecstack" "-L" "/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-o" "src/nouveau/compiler/nak" "-Wl,--gc-sections" "-pie" "-Wl,-z,relro,-z,now" "-Wl,-O1" "-Wno-unused-command-line-argument" "src/nouveau/winsys/libnouveau_ws.a" "src/nouveau/headers/libnvidia_headers_c.a" "src/compiler/libcompiler.a" "src/util/libmesa_util.a" "src/util/libmesa_util_sse41.a" "src/util/blake3/libblake3.a" "src/c11/impl/libmesa_util_c11.a" "/usr/lib/x86_64-linux-gnu/libdrm.so" "/usr/lib/x86_64-linux-gnu/libz.so" "-pthread" "/lib/x86_64-linux-gnu/libzstd.so" "/usr/lib/x86_64-linux-gnu/libunwind.so" "-pthread" "-pthread" "-L/usr/lib/llvm-15/lib/clang/15.0.6" "-L/usr/bin/../lib/gcc/x86_64-linux-gnu/12" "-L/usr/lib/gcc/x86_64-linux-gnu/12" "-L/usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../lib64" "-L/usr/lib64" "-L/lib/x86_64-linux-gnu" "-L/usr/lib/x86_64-linux-gnu" "-L/lib/../lib64" "-L/usr/lib/../lib64" "-L/lib" "-L/usr/lib" "-lstdc++" "-Wl,-rpath,$ORIGIN/:$ORIGIN/../../../subprojects/paste-1.0.14:/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib" "-Wl,-rpath-link,/builds/dh/mesa/_build/src/nouveau/compiler:/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib" "-Wl,-rpath-link,/builds/dh/mesa/_build/subprojects/paste-1.0.14:/root/.rustup/toolchains/1.76.0-2024-02-08-x86_64-unknown-linux-gnu/lib"
  = note: mold: fatal: failed to load plugin : /usr/bin/ld: undefined symbol: onload
          clang: error: linker command failed with exit code 1 (use -v to see invocation)       

[rui314]

The linker complains that you passed /usr/bin/ld as an argument for the --plugin option, which takes a linker plugin .so file. You want to check what linker options you are passing.

[fsvm88]

I have a similar error, not sure if/how it is related to okias' one.

I am on Gentoo, using clang 19.1.7 as system compiler. I recompiled my whole system with mold using with the following flags:

CFLAGS="-O3 -march=native -pipe -glldb -flto=thin -fwhole-program-vtables -gline-tables-only"
CXXFLAGS="${CFLAGS}"
LDFLAGS="-Wl,-O3,-z,now,--as-needed,--lto-O3,--icf=safe -fuse-ld=mold"

I have noticed quite a few packages that fail at link stage, I suspect because clang is not detecting that it should pass the LTO options to the linker. This happens in some packages using libtool, but the simplest reproducer I could find is sys-process/schedtool.

If I use the flags above, I get this invocation at link stage:

clang-19 -Wl,-O3,-z,now,--as-needed,--lto-O3,--icf=safe -fuse-ld=mold -v  schedtool.o error.o   -o schedtool
clang version 19.1.7+libcxx
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm/19/bin
Configuration file: /etc/clang/x86_64-pc-linux-gnu-clang.cfg
System configuration file directory: /etc/clang
User configuration file directory: /var/tmp/portage/sys-process/schedtool-1.3.0-r2/homedir/.config/clang
Selected GCC installation: /usr/lib/gcc/x86_64-pc-linux-gnu/14
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
Found HIP installation: /usr, version 6.3.42131
 "/usr/bin/ld.mold" --hash-style=gnu --eh-frame-hdr -m elf_x86_64 -pie -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o schedtool /usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../lib64/Scrt1.o /usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../lib64/crti.o /usr/lib/llvm/19/bin/../../../../lib/clang/
19/lib/linux/clang_rt.crtbegin-x86_64.o -L/usr/lib/gcc/x86_64-pc-linux-gnu/14 -L/usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../lib64 -L/lib/../lib64 -L/usr/lib/../lib64 -L/usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../x86_64-pc-linux-gnu/lib -L/lib -L/usr/lib -z relro -z now -O3 -z now --as-
needed --lto-O3 --icf=safe schedtool.o error.o /usr/lib/llvm/19/bin/../../../../lib/clang/19/lib/linux/libclang_rt.builtins-x86_64.a --as-needed -lunwind --no-as-needed -lc /usr/lib/llvm/19/bin/../../../../lib/clang/19/lib/linux/libclang_rt.builtins-x86_64.a --as-needed -lunwind --no-as-needed
 /usr/lib/llvm/19/bin/../../../../lib/clang/19/lib/linux/clang_rt.crtend-x86_64.o /usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../lib64/crtn.o
mold: fatal: failed to load plugin : /usr/bin/ld.mold: undefined symbol: onload
clang-19: error: linker command failed with exit code 1 (use -v to see invocation)

If I override LDFLAGS by adding the LTO options ->

export LDFLAGS="-Wl,-O3,-z,now,--as-needed,--lto-O3,--icf=safe -fuse-ld=mold -v -flto=thin -fwhole-program-vtables"

I get a proper link instead:

clang-19 -Wl,-O3,-z,now,--as-needed,--lto-O3,--icf=safe -fuse-ld=mold -v -flto=thin -fwhole-program-vtables  schedtool.o error.o   -o schedtool
clang version 19.1.7+libcxx
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm/19/bin
Configuration file: /etc/clang/x86_64-pc-linux-gnu-clang.cfg
System configuration file directory: /etc/clang
User configuration file directory: /var/tmp/portage/sys-process/schedtool-1.3.0-r2/homedir/.config/clang
Selected GCC installation: /usr/lib/gcc/x86_64-pc-linux-gnu/14
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
Found HIP installation: /usr, version 6.3.42131
 "/usr/bin/ld.mold" --hash-style=gnu --eh-frame-hdr -m elf_x86_64 -pie -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o schedtool /usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../lib64/Scrt1.o /usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../lib64/crti.o /usr/lib/llvm/19/bin/../../../../lib/clang/19/lib/linux/clang_rt.crtbegin-x86_64.o -L/usr/lib/gcc/x86_64-pc-linux-gnu/14 -L/usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../lib64 -L/lib/../lib64 -L/usr/lib/../lib64 -L/usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../x86_64-pc-linux-gnu/lib -L/lib -L/usr/lib -plugin /usr/lib/llvm/19/bin/../lib64/LLVMgold.so -plugin-opt=mcpu=x86-64 -plugin-opt=thinlto -z relro -z now -O3 -z now --as-needed --lto-O3 --icf=safe schedtool.o error.o /usr/lib/llvm/19/bin/../../../../lib/clang/19/lib/linux/libclang_rt.builtins-x86_64.a --as-needed -lunwind --no-as-needed -lc /usr/lib/llvm/19/bin/../../../../lib/clang/19/lib/linux/libclang_rt.builtins-x86_64.a --as-needed -lunwind --no-as-needed /usr/lib/llvm/19/bin/../../../../lib/clang/19/lib/linux/clang_rt.crtend-x86_64.o /usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../lib64/crtn.o
>>> Source compiled.

The difference that I could find between the two invocations is that on the successful one clang supplies -plugin-opt=mcpu=x86-64 -plugin-opt=thinlto, but in the failing one it does not. EDIT: also -plugin /usr/lib/llvm/19/bin/../lib64/LLVMgold.so is correctly supplied in the successful build.

I'm not sure if this is an issue with clang or mold - would you be able to point me in the right direction?

[rui314]

@fsvm88 Can you build it with GNU ld? In other words, can you build it if you replace -fuse-ld=mold with -fuse-ld=bfd?

[fsvm88]

I get a file format not recognized error ->

clang-19 -Wl,-O3,-z,now,--as-needed -v -fuse-ld=bfd  schedtool.o error.o   -o schedtool
clang version 19.1.7+libcxx
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm/19/bin
Configuration file: /etc/clang/x86_64-pc-linux-gnu-clang.cfg
System configuration file directory: /etc/clang
User configuration file directory: /var/tmp/portage/sys-process/schedtool-1.3.0-r2/homedir/.config/clang
Selected GCC installation: /usr/lib/gcc/x86_64-pc-linux-gnu/14
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
Found HIP installation: /usr, version 6.3.42131
 "/usr/bin/x86_64-pc-linux-gnu-ld.bfd" --hash-style=gnu --eh-frame-hdr -m elf_x86_64 -pie -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o schedtool /usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../lib64/Scrt1.o /usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../lib64/crti.o /usr/lib/llvm/19/bin/../../../../lib/clang/19/lib/linux/clang_rt.crtbegin-x86_64.o -L/usr/lib/gcc/x86_64-pc-linux-gnu/14 -L/usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../lib64 -L/lib/../lib64 -L/usr/lib/../lib64 -L/usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../x86_64-pc-linux-gnu/lib -L/lib -L/usr/lib -z relro -z now -O3 -z now --as-needed schedtool.o error.o /usr/lib/llvm/19/bin/../../../../lib/clang/19/lib/linux/libclang_rt.builtins-x86_64.a --as-needed -lunwind --no-as-needed -lc /usr/lib/llvm/19/bin/../../../../lib/clang/19/lib/linux/libclang_rt.builtins-x86_64.a --as-needed -lunwind --no-as-needed /usr/lib/llvm/19/bin/../../../../lib/clang/19/lib/linux/clang_rt.crtend-x86_64.o /usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../lib64/crtn.o
schedtool.o: file not recognized: file format not recognized

It seems also in this case the flags are not passed down by clang. I'm not sure whether this is expected though: when clang is called for linking, I don't think it reads the files at all, but rather just creates the proper linker invocation and executes it. LLD seems to not require a linker plugin if I understand it correctly, so it avoids the problem and relies on the content of the files.

[rui314]

LLVM lld is, as a subproject of LLVM, supports LLVM bitcode natively, so it doesn't require a plugin to read LLVM object files. (By the way, on the other hand, lld supports only the corresponding version of LLVM. If you are using clang-19, you need to use lld-19 for LTO.)

GNU ld and mold don't support LLVM bitcode natively. It's clang's responsibility to pass a plugin path to the linker. That's what the --flto option usually do.

Maybe your clang doesn't come with a plugin file. The plugin file is usually named LLVMgold.so. If that file is missing, you need to reinstall or rebuild your clang so that you'll have that plugin file.

[fsvm88]

On Gentoo this is configured via binutils-plugin USE on llvm-core/llvm, that pulls in a dependency on llvm-core/llvmgold, which deploys a symlink for autoloading the plugin.

The plugin is built in LLVM itself, and it is present on my system -> /usr/lib/llvm/19/lib64/LLVMgold.so

I did some deeper digging, it seems this is a known issue with non-LLD linkers. CFLAGS need to be part of LDFLAGS if the compiler is used to invoke the linker.