Linking error with libxml2

[dreisicht]

I tried setting up toolchains_llvm in a minimal repo on a current CachyOS. On an MacOS it works flawlessly.

This is the MODULE.bazel

module(
    name = "terrain_displacer",
    version = "0.1.0",
)

bazel_dep(name = "rules_cc", version = "0.2.16")

bazel_dep(name = "toolchains_llvm", version = "1.6.0")
llvm = use_extension("@toolchains_llvm//toolchain/extensions:llvm.bzl", "llvm")
llvm.toolchain(
   llvm_version = "21.1.6",
)
use_repo(llvm, "llvm_toolchain")
register_toolchains("@llvm_toolchain//:all")

A simple BUILD.bazel

load("@rules_cc//cc:defs.bzl", "cc_binary")

package(default_visibility = ["//visibility:public"])

cc_binary(
    name = "main",
    srcs = ["main.cc"],
)

A C++ test file

#include <iostream>

int main(int argc, char *argv[]) {
  std::cout << "hi";
  return 0;
}

Where I'm getting the error

ERROR: /home/peterbaintner/repos/terrain_displacer/src/BUILD.bazel:16:10: Linking src/scratchpad failed: (Exit 1): cc_wrapper.sh failed: error executing CppLink command (from cc_binary rule target //src:scratchpad) external/toolchains_llvm++llvm+llvm_toolchain/bin/cc_wrapper.sh @bazel-out/k8-fastbuild/bin/src/scratchpad-0.params

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
external/toolchains_llvm++llvm+llvm_toolchain_llvm/bin/ld.lld: error while loading shared libraries: libxml2.so.2: cannot open shared object file: No such file or directory
clang: error: unable to execute command: No such file or directory

[keith]

you need to globally install libxml2, this might be fixed in a future llvm release llvm/llvm-project#166867

[dreisicht]

libxml2 is actually globally installed, that's why I'm so suprised. I figured I would have to set the LD_LIBRARY_PATH or providing an explicit sysroot, but none of my experiments were successful.

Repository      : cachyos-core-znver4
Name            : libxml2
Version         : 2.15.1-5.1
Description     : XML C parser and toolkit
Architecture    : x86_64_v4
URL             : https://gitlab.gnome.org/GNOME/libxml2/-/wikis/home
Licenses        : MIT
Groups          : None
Provides        : libxml2.so=16-64
Depends On      : bash  glibc  icu  readline  zlib  libicuuc.so=78-64
Optional Deps   : python: Python bindings
Conflicts With  : None
Replaces        : None
Download Size   : 855,21 KiB
Installed Size  : 3307,28 KiB
Packager        : CachyOS <admin@cachyos.org>
Build Date      : So 11 Jan 2026 10:26:19 CET
Validated By    : SHA-256 Sum  Signature

[keith]

where is it installed? you can check the rpaths / ldd of the clang binary that is downloaded, could definitely be looking in a place which is different from that distros. I've looked into this before and there's something weird about how some distros have the 2 in the binary name and some dont

[dreisicht]

Apart from application who bring their own libraries, I have two installed system wide:

usr/lib/libxml2.so.16.1.1
usr/lib32/libxml2.so.16.1.1

This is the output of the ldd command with clang:

❯ ldd 2505e650c2bd32e39eab40d9d3efe502/external/toolchains_llvm++llvm+llvm_toolchain_llvm/bin/clang-21
        linux-vdso.so.1 (0x00007f93530d0000)
        libm.so.6 => /usr/lib/libm.so.6 (0x00007f9352fb2000)
        libz.so.1 => /usr/lib/libz.so.1 (0x00007f9352f78000)
        libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00007f9345a00000)
        libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00007f9352f43000)
        libc.so.6 => /usr/lib/libc.so.6 (0x00007f9345600000)
        /lib64/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x00007f93530d2000)

[keith]

you need to ldd ld.lld, that's the binary that references it

[dreisicht]

Sorry, I wasn' focused when replying. This is the proper output:

 ldd external/toolchains_llvm++llvm+llvm_toolchain_llvm/bin/ld.lld
        linux-vdso.so.1 (0x00007ff12aa7a000)
        libxml2.so.2 => not found
        libm.so.6 => /usr/lib/libm.so.6 (0x00007ff12a95c000)
        libz.so.1 => /usr/lib/libz.so.1 (0x00007ff12a922000)
        libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00007ff122e00000)
        libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00007ff1231cb000)
        libc.so.6 => /usr/lib/libc.so.6 (0x00007ff122a00000)
        /lib64/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x00007ff12aa7c000)

Looks like the problem is that it expects the libxml2.so.2 but I only have libxml2.so.16.1.1