clang_arg don't work when used to include the header file

[try-agaaain]

I defined bindgen as follows:

     let wasm_bindings = bindgen::Builder::default()
         // The input header we would like to generate
         // bindings for.
         .header("../../wasm-runtime/include/bpf-api.h")
         .clang_arg("-I")
         .clang_arg("../../third_party/wasm-micro-runtime/core/iwasm/include/wasm_export.h")
         .clang_arg("-x")
         .clang_arg("c++")
         // Tell cargo to invalidate the built crate whenever any of the
         // included header files changed.
         .parse_callbacks(Box::new(bindgen::CargoCallbacks))
         // Finish the builder and generate the bindings.
         .generate()
         // Unwrap the Result and panic on failure.
         .expect("Unable to generate wasm-bpf bindings");

In the header file ../../wasm-runtime/include/bpf-api.h, you need to reference another header file ../../third_party/wasm-micro-runtime/core/iwasm/include /wasm_export.h, so I added this header file to the search path via clang_arg, but it didn't work.

The following error occurred in the terminal:

   --- stderr
   ../../wasm-runtime/include/bpf-api.h:16:10: fatal error: 'wasm_export.h' file not found
   thread 'main' panicked at 'Unable to generate wasm-bpf bindings: ClangDiagnostic("../../wasm-runtime/include/bpf-api.h:16:10: fatal error: 'wasm_export.h' file not found\n")', build.rs:43:10
   stack backtrace:
      0: rust_begin_unwind
                at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/panicking.rs:575:5
      1: core::panicking::panic_fmt
                at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/core/src/panicking.rs:64:14
      2: core::result::unwrap_failed
                at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/core/src/result.rs:1791:5
      3: core::result::Result<T,E>::expect
      4: build_script_build::main
      5: core::ops::function::FnOnce::call_once
   note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
make: *** [Makefile:7: build] Error 101

I also tried defining BINDGEN_EXTRA_CLANG_ARGS="-I../../third_party/wasm-micro-runtime/core/iwasm/include/wasm_export.h", but that didn't work either.

I wonder know why doesn't clang_arg work? Any advice would be greatly appreciated. (I tried to find related issues, but it didn't solve my problem.)

[pvdrz]

I think that's because -I is used to include whole directories, you want to use -include instead:

  -I <dir>                Add directory to the end of the list of include search paths
  -include <file>         Include file before parsing

Or you could use the header method again instead:

     let wasm_bindings = bindgen::Builder::default()
         // The input header we would like to generate
         // bindings for.
         .header("../../wasm-runtime/include/bpf-api.h")
         .header("../../third_party/wasm-micro-runtime/core/iwasm/include/wasm_export.h")
         .clang_arg("-x")
         .clang_arg("c++")
         // Tell cargo to invalidate the built crate whenever any of the
         // included header files changed.
         .parse_callbacks(Box::new(bindgen::CargoCallbacks))
         // Finish the builder and generate the bindings.
         .generate()
         // Unwrap the Result and panic on failure.
         .expect("Unable to generate wasm-bpf bindings");

Let me know if this fixes your problem.

[try-agaaain]

Thank you for your suggestion. When I use the -I parameter, I can find wasm_export.h normally and smoothly, which solves my problem.

However, when using header or -include, wasm_export.h still cannot be found, which is a bit strange.

[pvdrz]

Yeah that's expected. The issue is that -include actually includes the file you pass to it instead of just telling C that the file is available somewhere. Basically doing -include long_path is the same as putting #include "long_path" at the top of your headers. When you do -I long_path this tells the compiler that long_path is one of the directories where it should search for headers.

So you have two options:

• Remove the #include from your headers and pass -include.
• Just use -I with the directory.