Static linking doesn't work

[theoparis]

Caused by:
  process didn't exit successfully: `/home/theo/dev/raknet/target/debug/build/clang-sys-6b084d6bff3d9148/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at /home/theo/.cargo/git/checkouts/clang-sys-67ca2c90881f88fe/ab99460/build/static.rs:90:9:
  could not find any static libraries
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

After I fixed #168 in my fork, I realized clang-sys tries to find libclang.a which doesn't exist. Instead it should be using all of the clang libraries (libclang*.a, not a singular libclang.a)

[theoparis]

Is this library still being maintained? I am still encountering my two issues and this breaks the entire rust ecosystem on my end - meaning everything that relies on bindgen is unusable. Additionally it seems like there are issues from 2021 with no response....

Maybe this project could get moved to the rust-lang organization in the future?

[KyleMayes]

I'm pretty sure static linking only works when libclang.a is available, but this isn't included in most builds.
(e.g., sudo apt install libclang-dev on Ubuntu won't include libclang.a).

I'm looking into building libclang.a from source and seeing if static linking still works with that approach.

If that is the case, I think the documentation and error messages can be improved to make this more clear.

[theoparis]

Yeah, I did try using clang built from source but maybe I missed a cmake option to build everything as a single libclang.a file, not sure. Currently I have a libclang.so and a bunch of libclangXYZ.a libraries.

[KyleMayes]

Looks like you need to turn the LIBCLANG_BUILD_STATIC option on:
https://github.com/llvm/llvm-project/blob/cbd8031baa62f20d8513f084104180f9d49d763d/clang/tools/libclang/CMakeLists.txt#L87-L88

And have PIC disabled:
https://github.com/llvm/llvm-project/blob/cbd8031baa62f20d8513f084104180f9d49d763d/clang/tools/libclang/CMakeLists.txt#L118-L120

[KyleMayes]

This worked for me (in a freshly cloned llvm-project repo):

cmake -S llvm -B build -G Ninja -DLLVM_ENABLE_PROJECTS=clang -DLIBCLANG_BUILD_STATIC=ON
ninja -C build

That (eventually) produced build/lib/libclang.a.

Then, after setting the LLVM_CONFIG_PATH environment variable to point to the newly built llvm-config, I was able to run cargo test --features static in clang-sys with no issues.

(Note: It was taking ages to link the zillions of LLVM/Clang static libraries until I switched to nightly Rust which uses lld instead of ld for linking)

[KyleMayes]

I've updated the error message for when static linking fails to find libclang.a and added a section to the README about how most users will probably need to build libclang.a themselves since it usually isn't included in most distributions of LLVM / Clang.