Unable to compile on mac os Catalina 10.15.7

[magom001]

During compilation

   Compiling thiserror v1.0.22
   Compiling leptonica-sys v0.3.3
   Compiling tesseract-sys v0.5.4
error: failed to run custom build command for `tesseract-sys v0.5.4`

Caused by:
  process didn't exit successfully: `/Users/a18678299/Documents/test-rc/target/debug/build/tesseract-sys-04ae1979553eebf3/build-script-build` (exit code: 101)
  --- stdout
  cargo:rustc-link-lib=tesseract

  --- stderr
  /usr/local/include/tesseract/publictypes.h:33:1: error: unknown type name 'constexpr'
  /usr/local/include/tesseract/publictypes.h:38:1: error: unknown type name 'constexpr'
  /usr/local/include/tesseract/publictypes.h:40:1: error: unknown type name 'constexpr'
  /usr/local/include/tesseract/publictypes.h:45:1: error: unknown type name 'constexpr'
  /usr/local/include/tesseract/publictypes.h:33:1: error: unknown type name 'constexpr', err: true
  /usr/local/include/tesseract/publictypes.h:38:1: error: unknown type name 'constexpr', err: true
  /usr/local/include/tesseract/publictypes.h:40:1: error: unknown type name 'constexpr', err: true
  /usr/local/include/tesseract/publictypes.h:45:1: error: unknown type name 'constexpr', err: true
  thread 'main' panicked at 'Unable to generate public types bindings: ()', /Users/a18678299/.cargo/registry/src/github.com-1ecc6299db9ec823/tesseract-sys-0.5.4/build.rs:68:10
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

I am not an expert on rust. But how come it does not understand constexpr?

[ccouzens]

Hi @magom001

On my Mac Laptop (also Catalina 10.15.7), I see the same error. It used to work.

I think the version of clang might have been updated recently on Mac to Apple clang version 12.0.0 (clang-1200.0.32.28).

I'm using the brew package manager. I can install clang 11 using it.

brew install llvm tesseract leptonica

Then, I can build tesseract-sys using a couple extra environment variables:

PATH="/usr/local/opt/llvm/bin:$PATH" BINDGEN_EXTRA_CLANG_ARGS='-I"/usr/local/Cellar/tesseract/4.1.1/include" -I"/usr/local/Cellar/leptonica/1.80.0/include"' cargo test

Does that work for you?

But how come it does not understand constexpr?

I think this may be an issue with how the bindgen crate interacts with clang. Maybe clang 12 is too new, and it will be fixed in an update of bindgen.

[magom001]

Thanks for your feedback! Indeed it does work with clang 11

TOML

[package]
name = "tess-build"

[dependencies]
tesseract = "0.6.2"

main.rs

fn main() {
    let text = tesseract::ocr("<PATH_TO_DIR>/tess-build/img.png", "eng").unwrap();
    println!("{}", text);
}

running with

PATH="/usr/local/opt/llvm/bin:$PATH" BINDGEN_EXTRA_CLANG_ARGS='-I"/usr/local/Cellar/tesseract/4.1.1/include" -I"/usr/local/Cellar/leptonica/1.80.0/include"' cargo run

[ccouzens]

Good that it worked :+1:

I'll try an issue about it clang 12 and constexpr on the bindgen project.

[matthewleon]

As I've mentioned in the related issue https://github.com/rust-lang/rust-bindgen/issues/1948 this is still failing in the same way on clang 13.