onig_sys v69.2.0 fails to build on Centos with "Unable to find libclang"

[pcallahan-r7]

onig_sys v69.1.0 compiles ok.

error: failed to run custom build command for `onig_sys v69.2.0`
process didn't exit successfully: `/libtcellagent/docker_linux_target/debug/build/onig_sys-76e23c1154f13aa7/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:997:5
note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.

warning: build failed, waiting for other jobs to finish...
error: build failed

[pcallahan-r7]

Similar error on Windows:

error: failed to run custom build command for `onig_sys v69.2.0`
Caused by:
  process didn't exit successfully: `D:\git\libtcellagent\target\debug\build\onig_sys-d53bdd35ac8a2bf3\build-script-build` (exit code: 101)
--- stdout
cargo:warning=couldn't execute `llvm-config --prefix` (error: The system cannot find the file specified. (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: [\'clang.dll\', \'libclang.dll\'], set the `LIBCLANG_PATH` environment variable to a path where one of these files can be found (invalid: [])"', src\libcore\result.rs:999:5
note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
warning: build failed, waiting for other jobs to finish...
error: build failed

[sophiajt]

This also causes onig 4.3 to fail. It appears that 69.2 includes breaking changes from 69.1.

This may indicate that 69.2 is not semver compatible with 69.1 (and potentially should be called 70.0 instead)

[iwillspeak]

Yeah, it isn’t compatible. The build changed quite a lot. The major version is supposed to contain the underlying onig version. Can provably bump it all the way to 690 though

[iwillspeak]

Hopefully this should be worked around by pinning the onig_sys version in #112

[iwillspeak]

For compiling with onig 5.x at the moment you'll need the dependencies for bindgen available at build time too.

[getaaron]

On Debian I worked around this by running apt-get install llvm before installing onig_sys 🤷‍♂️

[iwillspeak]

While the work-around for this issue with newer versions of onig is to either use an older crate version or ensure LLVM & clang are installed I'm going to treat this issue as "compilation on common targets shouldn't require bindgen on every build" instead. I'll work on a branch over the next few days to pull together some of @kornelski 's bindgen-related changes and refactor the way we do compile-time binding generation.