build.rs

// build.rs
//
// Compiles the small C++ shim (`src/mcpnet.cpp`) that wraps the header-only
// mcpnet kernel templates, and wires it up to the Rust side through `cxx`.

use std::path::PathBuf;

fn main() {
    let crate_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"));

    let mcpnet_root = crate_dir.join("src").join("mcpnet");
    let mcpnet_include = mcpnet_root.join("include");
    let splash_include = mcpnet_root.join("ext").join("splash").join("include");
    let fmt_include = mcpnet_root
        .join("ext")
        .join("splash")
        .join("ext")
        .join("fmt")
        .join("include");

    for path in [&mcpnet_include, &splash_include, &fmt_include] {
        assert!(
            path.exists(),
            "missing include directory: {} (did you run `git submodule update --init --recursive`?)",
            path.display()
        );
    }

    let mut build = cxx_build::bridge("src/lib.rs");
    build
        .file("src/mcpnet.cpp")
        .include(crate_dir.join("include"))
        .include(&mcpnet_include)
        .include(&splash_include)
        .include(&fmt_include)
        .std("c++14")
        .flag_if_supported("-Wno-unused-parameter")
        .flag_if_supported("-Wno-unused-variable")
        .flag_if_supported("-Wno-unused-but-set-variable")
        .flag_if_supported("-Wno-sign-compare")
        .flag_if_supported("-Wno-deprecated-declarations")
        .flag_if_supported("-Wimplicit-fallthrough=0")
        .flag_if_supported("-ffast-math")
        .flag_if_supported("-funroll-loops");

    build.compile("mcpnet_rs");

    println!("cargo:rerun-if-changed=src/lib.rs");
    println!("cargo:rerun-if-changed=src/mcpnet.cpp");
    println!("cargo:rerun-if-changed=include/mcpnet.h");
    println!("cargo:rerun-if-changed=build.rs");
}