rust-lld: error: undefined symbol: __gxx_personality_v0

[hasenbanck]

We encountered a bug, where the experimental rust-lld currently activated under nightly linux / x86-64, can't links certain executables in release mode with the "intel_tex_2" crate. Switching to the old linker solves the problem.

I created a small repository which includes a minimal example.

https://github.com/hasenbanck/rust_lld_bug

It will crash when compiled via:

cargo run --release

Normaly it should compile fine, but we instead get the following error:

error: linking with `cc` failed: exit status: 1
  |
  = note: LC_ALL="C" PATH=".....*A LOT OF PATHS*...."
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: rust-lld: error: undefined symbol: __gxx_personality_v0
          >>> referenced by ispc_texcomp_astc.cpp
          >>>               ispc_texcomp_astc.o:(DW.ref.__gxx_personality_v0) in archive /mnt/c/Development/rust_lld_bug/target/release/deps/libintel_tex_2-2caaaa92d5e41391.rlib
          collect2: error: ld returned 1 exit status

error: could not compile `rust_lld_bug` (bin "rust_lld_bug") due to 1 previous error

We used the nightly toolchain 2025-01-07, but older nightly versions are also affected.
We reproduces this error under WSL Ubuntu 24.04 and Fedora 41 running on bare metal.

The old linker works fine:

RUSTFLAGS="-Z linker-features=-lld" cargo run --release

[bjorn3]

__gxx_personality_v0 is the C++ personality function which is defined by the C++ standard library. I can't find where intel_tex_2 tells the linker to link against the C++ standard library. Can you check if in part of the linker invocation that you omitted there is a -lc++ or -lstdc++ or something like argument that?

[hasenbanck]

  Downloaded num_cpus v1.16.0
  Downloaded ispc_rt v2.0.1
  Downloaded libc v0.2.169
  Downloaded intel_tex_2 v0.4.0
  Downloaded 4 crates (9.7 MB) in 0.74s (largest was `intel_tex_2` at 8.9 MB)
   Compiling libc v0.2.169
   Compiling num_cpus v1.16.0
   Compiling ispc_rt v2.0.1
   Compiling intel_tex_2 v0.4.0
   Compiling rust_lld_bug v0.1.0 (/home/a_user/Development/rust_lld_bug)
error: linking with `cc` failed: exit status: 1
  |
  = note: LC_ALL="C" PATH="/home/a_user/.rustup/toolchains/nightly-2025-01-07-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin:/home/a_user/.rustup/toolchains/nightly-2025-01-07-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin/self-contained:/home/a_user/.cargo/bin:/home/a_user/.local/bin:/home/a_user/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin" VSLANG="1033" "cc" "-m64" "/tmp/rustckQ50hQ/symbols.o" "<2 object files omitted>" "-Wl,--as-needed" "-Wl,-Bstatic" "/home/a_user/Development/rust_lld_bug/target/release/deps/{libintel_tex_2-2caaaa92d5e41391.rlib,libispc_rt-c1f667297e82208b.rlib,libnum_cpus-b5fa6fd5af20baf4.rlib,liblibc-49da99225b5d9d58.rlib}" "/home/a_user/.rustup/toolchains/nightly-2025-01-07-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/{libstd-d6f1d924b2f4233e.rlib,libpanic_unwind-00eb06e39850f679.rlib,libobject-d0382f11baa011b6.rlib,libmemchr-b7e2e2c1a7e4643d.rlib,libaddr2line-30ced7f1999cfa29.rlib,libgimli-3ee7e14c58e31ebd.rlib,librustc_demangle-a4f649bba77ffcc5.rlib,libstd_detect-c89a3ce7ad7c3dbd.rlib,libhashbrown-e1ce1d3d110c6707.rlib,librustc_std_workspace_alloc-e0604fecbf0f39dc.rlib,libminiz_oxide-0a9c6172f04822cc.rlib,libadler2-14a33f7117abcee7.rlib,libunwind-24c16adbe5e57356.rlib,libcfg_if-d2688d4a5c8e415b.rlib,liblibc-8ff7ba6d97853f27.rlib,liballoc-5c001d095eb077ec.rlib,librustc_std_workspace_core-395a38b8e0851c9b.rlib,libcore-d453bab70303062c.rlib,libcompiler_builtins-dd545221bb4f4734.rlib}" "-Wl,-Bdynamic" "-lgcc_s" "-lutil" "-lrt" "-lpthread" "-lm" "-ldl" "-lc" "-B/home/a_user/.rustup/toolchains/nightly-2025-01-07-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin/gcc-ld" "-fuse-ld=lld" "-Wl,--eh-frame-hdr" "-Wl,-z,noexecstack" "-L" "/home/a_user/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/intel_tex_2-0.4.0/src/ispc" "-L" "/home/a_user/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/intel_tex_2-0.4.0/src/ispc" "-L" "/home/a_user/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/intel_tex_2-0.4.0/src/ispc" "-L" "/home/a_user/.rustup/toolchains/nightly-2025-01-07-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-o" "/home/a_user/Development/rust_lld_bug/target/release/deps/rust_lld_bug-8ac7a768a1ddcd3d" "-Wl,--gc-sections" "-pie" "-Wl,-z,relro,-z,now" "-Wl,-O1" "-Wl,--strip-debug" "-nodefaultlibs"
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: rust-lld: error: undefined symbol: __gxx_personality_v0
          >>> referenced by ispc_texcomp_astc.cpp
          >>>               ispc_texcomp_astc.o:(DW.ref.__gxx_personality_v0) in archive /home/a_user/Development/rust_lld_bug/target/release/deps/libintel_tex_2-2caaaa92d5e41391.rlib
          collect2: error: ld returned 1 exit status


error: could not compile `rust_lld_bug` (bin "rust_lld_bug") due to 1 previous error

Here is the full error output from a fresh Fedora 41 installaction. I can't see any -lc++ or -lstdc++

Just want to add that the default linker on stable for linux, macos and windows link this project fine.

I'm not deep into the topic of linking, but I think what happens here is, that code is stripped out by the other linker, which is never actually used by intel-tex-rs-2 (see the comment in the build script).

rust-lld is then trying to link the code that needs the C++ standard library, where as the other linker don't do that, since they stripped that code out already.

The question is now, what the expected behavior in this case is, especially in light of the different behavior on stable (of course intel-tex-rs-2 could remove that code, since it's not implemented anyhow).

[bjorn3]

I think it is expected that you may get an error about unresolved symbols if those are referenced by a function even if that function ends up getting discarded in the end. We don't guarantee that we enable --gc-sections to discard unused functions and even have an option to disable this using -Clink-dead-code=yes.