How to Debug Build Script (build.rs) Issues

Debug build.rs issues by running cargo build -vv to see the exact command line arguments and environment variables passed to your build script.

cargo build -vv

If the script fails due to missing dependencies or environment variables, check the RUSTC and OUT_DIR variables printed in the verbose output, then add println!("cargo:warning={}", "Your debug message"); to your build.rs to confirm execution order.

A build script is a small program that runs before your main code to set up the environment or generate files. If it breaks, your whole project stops building. Running the build with extra details shows you exactly what the script is trying to do and where it fails, like a mechanic listening to an engine to find the noise.