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Fixing Rust compilation issues caused by missing packages, part 2

This series of posts covers a few different Rust compilation errors caused by missing system packages and how to fix them.

You can find the first post in this series here.

libclang.so compilation error

Abbreviated error:

Unable to find libclang

Full error:

error: failed to run custom build command for `onig_sys v69.2.0`

Caused by:
  process didn't exit successfully: `/tmp/cargo-installuq50Y1/release/build/onig_sys-c22eb0db51eb31e2/build-script-build` (exit code: 101)
--- stdout
cargo:warning=couldn't execute `llvm-config --prefix` (error: No such file or directory (os error 2))
cargo:warning=set the LLVM_CONFIG_PATH environment variable to a valid `llvm-config` executable

--- stderr
thread 'main' panicked at 'Unable to find libclang: "couldn\'t find any valid shared libraries matching: [\'libclang.so\', \'libclang-*.so\', \'libclang.so.*\'], set the `LIBCLANG_PATH` environment variable to a path where one of these files can be found (invalid: [])"', src/libcore/result.rs:1165:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.

This one is caused by the fact that Rust depends on libclang, and LLVM more generally. For more info on how Rust uses LLVM, see here and here.

Fixing the error

If you don’t have clang installed, the Rust compiler can’t do its thing. To fix the error, install clang via the libclang package.


sudo apt-get install libclang-dev

On CentOS/RHL/Fedora:

sudo yum install clang  # Or replace `yum` with `dnf`

Once complete, run cargo build again and verify that the error that mentions libclang no longer pops up. If it still does, try setting $LIBCLANG_PATH to point to the location where libclang.so is installed:

$ find /usr -iname "libclang.so" -print
$ export LIBCLANG_PATH="/usr/lib/llvm-6.0/lib/libclang.so:${LIBCLANG_PATH}"

Next up

You can check out part 3 of the series here.