Constant XLS_DSO_PATH 

pub const XLS_DSO_PATH: &str = "/does/not/exist/libxls.so";

Directory containing the libxls DSO.

*** DO NOT USE THIS VARIABLE FROM WITHIN YOUR build.rs ***

You might be tempted to write the following in your build.rs:

// DO NOT DO THIS IN YOUR build.rs!!
let dylib_dirpath = xlsynth_sys::XLS_DSO_PATH;
// set rpath to dylib_dirpath or something.

The problem is that build.rs is compiled for host, whereas if you’re setting an rpath (or something similar) you want to get the path from compiling xlsynth_sys for target. In other words, the above will break cross-compilation.

Instead, your build.rs should get the path from an envvar which:

// Do this from your build.rs instead.
let dylib_path = std::env::var("DEP_XLSYNTH_DSO_PATH").unwrap();

More details are available at https://doc.rust-lang.org/cargo/reference/build-script-examples.html#using-another-sys-crate.

(If you use this envvar from your crate proper – i.e. not from build.rs – then it’s perfectly fine.)