main.rs

//! rustbuild, the Rust build system
//!
//! This is the entry point for the build system used to compile the `rustc`
//! compiler. Lots of documentation can be found in the `README.md` file in the
//! parent directory, and otherwise documentation can be found throughout the `build`
//! directory in each respective module.

use std::env;

#[cfg(all(any(unix, windows), not(target_os = "solaris")))]
use bootstrap::t;
use bootstrap::{Build, Config, Subcommand, VERSION};

fn main() {
    let args = env::args().skip(1).collect::<Vec<_>>();
    let config = Config::parse(&args);

    #[cfg(all(any(unix, windows), not(target_os = "solaris")))]
    let mut build_lock;
    #[cfg(all(any(unix, windows), not(target_os = "solaris")))]
    let _build_lock_guard;
    #[cfg(all(any(unix, windows), not(target_os = "solaris")))]
    {
        let path = config.out.join("lock");
        build_lock = fd_lock::RwLock::new(t!(std::fs::File::create(&path)));
        _build_lock_guard = match build_lock.try_write() {
            Ok(lock) => lock,
            err => {
                drop(err);
                if let Some(pid) = get_lock_owner(&path) {
                    println!("warning: build directory locked by process {pid}, waiting for lock");
                } else {
                    println!("warning: build directory locked, waiting for lock");
                }
                t!(build_lock.write())
            }
        };
    }
    #[cfg(any(not(any(unix, windows)), target_os = "solaris"))]
    println!("warning: file locking not supported for target, not locking build directory");

    // check_version warnings are not printed during setup
    let changelog_suggestion =
        if matches!(config.cmd, Subcommand::Setup { .. }) { None } else { check_version(&config) };

    // NOTE: Since `./configure` generates a `config.toml`, distro maintainers will see the
    // changelog warning, not the `x.py setup` message.
    let suggest_setup = config.config.is_none() && !matches!(config.cmd, Subcommand::Setup { .. });
    if suggest_setup {
        println!("warning: you have not made a `config.toml`");
        println!(
            "help: consider running `./x.py setup` or copying `config.example.toml` by running \
            `cp config.example.toml config.toml`"
        );
    } else if let Some(suggestion) = &changelog_suggestion {
        println!("{}", suggestion);
    }

    let pre_commit = config.src.join(".git").join("hooks").join("pre-commit");
    Build::new(config).build();

    if suggest_setup {
        println!("warning: you have not made a `config.toml`");
        println!(
            "help: consider running `./x.py setup` or copying `config.example.toml` by running \
            `cp config.example.toml config.toml`"
        );
    } else if let Some(suggestion) = &changelog_suggestion {
        println!("{}", suggestion);
    }

    // Give a warning if the pre-commit script is in pre-commit and not pre-push.
    // HACK: Since the commit script uses hard links, we can't actually tell if it was installed by x.py setup or not.
    // We could see if it's identical to src/etc/pre-push.sh, but pre-push may have been modified in the meantime.
    // Instead, look for this comment, which is almost certainly not in any custom hook.
    if std::fs::read_to_string(pre_commit).map_or(false, |contents| {
        contents.contains("https://github.com/rust-lang/rust/issues/77620#issuecomment-705144570")
    }) {
        println!(
            "warning: You have the pre-push script installed to .git/hooks/pre-commit. \
                  Consider moving it to .git/hooks/pre-push instead, which runs less often."
        );
    }

    if suggest_setup || changelog_suggestion.is_some() {
        println!("note: this message was printed twice to make it more likely to be seen");
    }
}

fn check_version(config: &Config) -> Option<String> {
    let mut msg = String::new();

    let suggestion = if let Some(seen) = config.changelog_seen {
        if seen != VERSION {
            msg.push_str("warning: there have been changes to x.py since you last updated.\n");
            format!("update `config.toml` to use `changelog-seen = {}` instead", VERSION)
        } else {
            return None;
        }
    } else {
        msg.push_str("warning: x.py has made several changes recently you may want to look at\n");
        format!("add `changelog-seen = {}` at the top of `config.toml`", VERSION)
    };

    msg.push_str("help: consider looking at the changes in `src/bootstrap/CHANGELOG.md`\n");
    msg.push_str("note: to silence this warning, ");
    msg.push_str(&suggestion);

    Some(msg)
}

/// Get the PID of the process which took the write lock by
/// parsing `/proc/locks`.
#[cfg(target_os = "linux")]
fn get_lock_owner(f: &std::path::Path) -> Option<u64> {
    use std::fs::File;
    use std::io::{BufRead, BufReader};
    use std::os::unix::fs::MetadataExt;

    let lock_inode = std::fs::metadata(f).ok()?.ino();
    let lockfile = File::open("/proc/locks").ok()?;
    BufReader::new(lockfile).lines().find_map(|line| {
        //                       pid--vvvvvv       vvvvvvv--- inode
        // 21: FLOCK  ADVISORY  WRITE 359238 08:02:3719774 0 EOF
        let line = line.ok()?;
        let parts = line.split_whitespace().collect::<Vec<_>>();
        let (pid, inode) = (parts[4].parse::<u64>().ok()?, &parts[5]);
        let inode = inode.rsplit_once(':')?.1.parse::<u64>().ok()?;
        if inode == lock_inode { Some(pid) } else { None }
    })
}

#[cfg(not(any(target_os = "linux", target_os = "solaris")))]
fn get_lock_owner(_: &std::path::Path) -> Option<u64> {
    // FIXME: Implement on other OS's
    None
}