cfg may not work in build script

[zu1k]

I'm cross compiling from linux to windows, but I found it not work.

I checked the history issue and found that the problem is still unresolved.

However, in the course of my continuous testing, I found that the cfg conditional judgment in the build script does not work.

My Test Demo

// build.rs

#[cfg(target_os="windows")]
fn main() {
    panic!("target_os = windows")
}

#[cfg(windows)]
fn main() {
    panic!("windows")
}

#[cfg(unix)]
fn main() {
    panic!("unix")
}

host system

$ uname -a
Linux alex 5.13.19-2-MANJARO #1 SMP PREEMPT Sun Sep 19 21:31:53 UTC 2021 x86_64 GNU/Linux

target: x86_64-unknown-linux-gnu (local)

$ cargo build 
   Compiling target v0.1.0 (/data/projects/target)
error: failed to run custom build command for `target v0.1.0 (/data/projects/target)`

Caused by:
  process didn't exit successfully: `/data/projects/target/target/debug/build/target-fff5ba352ad7afdb/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at 'unix', build.rs:13:5
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

That's fine, however when cross compile...

target: x86_64-pc-windows-gnu (cross compile)

$ cargo build --target x86_64-pc-windows-gnu 
   Compiling target v0.1.0 (/data/projects/target)
error: failed to run custom build command for `target v0.1.0 (/data/projects/target)`

Caused by:
  process didn't exit successfully: `/data/projects/target/target/debug/build/target-fff5ba352ad7afdb/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at 'unix', build.rs:13:5
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

I expect it to output window or target_os = windows, but it panic at unix

My solution

I think it may be because some features were not determined when build.rs was compiled and the features not been passed to rustc.

I have found some environment variables from the documentation and they can be used to determine target and host.

use std::env;

fn main() {
    if env::var("PROFILE").unwrap() == "release" {
        if let Ok(_) = env::var("CARGO_CFG_WINDOWS") {
            let mut res = winres::WindowsResource::new();
            if let Ok(host) = env::var("HOST") {
                if host.contains("linux") {
                    res.set_toolkit_path("/usr/bin")
                        .set_windres_path("x86_64-w64-mingw32-windres");
                }
            }
            res.set_icon("res/copy-translator.ico").set_language(0x04);
            res.compile().unwrap();
        }
    }
}

Icons are still not set successfully when cross compile fron linux to windows

[zu1k]

Icons are still not set successfully when cross compile fron linux to windows

Solved by remove lib.rs

[BenjaminRi]

Cross-compilation should now work out of the box in v0.1.13 of my fork. I updated the README as well, it had some buggy instructions (target_os is the host OS when you compile build.rs).