build.rs

use fish_build_helper::{
    env_var, fish_build_dir, target_os, target_os_is_apple, target_os_is_bsd, target_os_is_cygwin,
    workspace_root,
};
use rsconf::Target;
use std::path::{Path, PathBuf};

fn main() {
    setup_paths();

    // Add our default to enable tools that don't go through CMake, like "cargo test" and the
    // language server.

    rsconf::set_env_value(
        "FISH_RESOLVED_BUILD_DIR",
        // If set by CMake, this might include symlinks. Since we want to compare this to the
        // dir fish is executed in we need to canonicalize it.
        fish_build_dir().canonicalize().unwrap().to_str().unwrap(),
    );

    // We need to canonicalize (i.e. realpath) the manifest dir because we want to be able to
    // compare it directly as a string at runtime.
    rsconf::set_env_value(
        "CARGO_MANIFEST_DIR",
        workspace_root().canonicalize().unwrap().to_str().unwrap(),
    );

    // Some build info
    rsconf::set_env_value("BUILD_TARGET_TRIPLE", &env_var("TARGET").unwrap());
    rsconf::set_env_value("BUILD_HOST_TRIPLE", &env_var("HOST").unwrap());
    rsconf::set_env_value("BUILD_PROFILE", &env_var("PROFILE").unwrap());

    // Per https://doc.rust-lang.org/cargo/reference/build-scripts.html#inputs-to-the-build-script,
    // the source directory is the current working directory of the build script
    rsconf::set_env_value("FISH_BUILD_VERSION", &get_version());

    fish_build_helper::rebuild_if_embedded_path_changed("share");

    let build = cc::Build::new();
    let mut target = Target::new_from(build).unwrap();
    // Keep verbose mode on until we've ironed out rust build script stuff
    target.set_verbose(true);
    detect_cfgs(&mut target);

    #[cfg(all(target_env = "gnu", target_feature = "crt-static"))]
    compile_error!(
        "Statically linking against glibc has unavoidable crashes and is unsupported. Use dynamic linking or link statically against musl."
    );
}

/// Check target system support for certain functionality dynamically when the build is invoked,
/// without their having to be explicitly enabled in the `cargo build --features xxx` invocation.
///
/// We are using [`rsconf::enable_cfg()`] instead of [`rsconf::enable_feature()`] as rust features
/// should be used for things that a user can/would reasonably enable or disable to tweak or coerce
/// behavior, but here we are testing for whether or not things are supported altogether.
///
/// This can be used to enable features that we check for and conditionally compile according to in
/// our own codebase, but [can't be used to pull in dependencies](0) even if they're gated (in
/// `Cargo.toml`) behind a feature we just enabled.
///
/// [0]: https://github.com/rust-lang/cargo/issues/5499
fn detect_cfgs(target: &mut Target) {
    for (name, handler) in [
        // Ignore the first entry, it just sets up the type inference.
        ("", &(|_: &Target| false) as &dyn Fn(&Target) -> bool),
        ("apple", &(|_| target_os_is_apple())),
        ("bsd", &(|_| target_os_is_bsd())),
        ("cygwin", &(|_| target_os_is_cygwin())),
        ("have_eventfd", &|target| {
            // FIXME: NetBSD 10 has eventfd, but the libc crate does not expose it.
            if target_os() == "netbsd" {
                false
            } else {
                target.has_header("sys/eventfd.h")
            }
        }),
        ("have_localeconv_l", &|target| {
            target.has_symbol("localeconv_l")
        }),
        ("have_pipe2", &|target| target.has_symbol("pipe2")),
        ("have_posix_spawn", &|target| {
            if matches!(target_os().as_str(), "openbsd" | "android") {
                // OpenBSD's posix_spawn returns status 127 instead of erroring with ENOEXEC when faced with a
                // shebang-less script. Disable posix_spawn on OpenBSD.
                //
                // Android is broken for unclear reasons
                false
            } else {
                target.has_header("spawn.h")
            }
        }),
        ("small_main_stack", &has_small_stack),
        ("using_cmake", &|_| {
            option_env!("FISH_CMAKE_BINARY_DIR").is_some()
        }),
        ("waitstatus_signal_ret", &|target| {
            target.r#if("WEXITSTATUS(0x007f) == 0x7f", &["sys/wait.h"])
        }),
    ] {
        rsconf::declare_cfg(name, handler(target));
    }
}

/// Rust sets the stack size of newly created threads to a sane value, but is at at the mercy of the
/// OS when it comes to the size of the main stack. Some platforms we support default to a tiny
/// 0.5 MiB main stack, which is insufficient for fish's MAX_EVAL_DEPTH/MAX_STACK_DEPTH values.
///
/// 0.5 MiB is small enough that we'd have to drastically reduce MAX_STACK_DEPTH to less than 10, so
/// we instead use a workaround to increase the main thread size.
fn has_small_stack(_: &Target) -> bool {
    #[cfg(not(any(target_os = "ios", target_os = "macos", target_os = "netbsd")))]
    return false;

    // NetBSD 10 also needs this but can't find pthread_get_stacksize_np.
    #[cfg(target_os = "netbsd")]
    return true;

    #[cfg(any(target_os = "ios", target_os = "macos"))]
    {
        use core::ffi;

        unsafe extern "C" {
            unsafe fn pthread_get_stacksize_np(thread: *const ffi::c_void) -> usize;
            unsafe fn pthread_self() -> *const ffi::c_void;
        }

        // build.rs is executed on the main thread, so we are getting the main thread's stack size.
        // Modern macOS versions default to an 8 MiB main stack but legacy OS X have a 0.5 MiB one.
        let stack_size = unsafe { pthread_get_stacksize_np(pthread_self()) };
        const TWO_MIB: usize = 2 * 1024 * 1024 - 1;
        stack_size <= TWO_MIB
    }
}

fn setup_paths() {
    #[cfg(windows)]
    use unix_path::{Path, PathBuf};

    fn overridable_path(
        env_var_name: &str,
        f: impl FnOnce(Option<String>) -> Option<PathBuf>,
    ) -> Option<PathBuf> {
        rsconf::rebuild_if_env_changed(env_var_name);
        let maybe_path = f(env_var(env_var_name));
        if let Some(path) = maybe_path.as_ref() {
            rsconf::set_env_value(env_var_name, path.to_str().unwrap());
        }
        maybe_path
    }

    fn join_if_relative(parent_if_relative: &Path, path: String) -> PathBuf {
        let path = PathBuf::from(path);
        if path.is_relative() {
            parent_if_relative.join(path)
        } else {
            path
        }
    }

    let prefix = overridable_path("PREFIX", |env_prefix| {
        Some(PathBuf::from(env_prefix.unwrap_or("/usr/local".to_owned())))
    })
    .unwrap();

    overridable_path("SYSCONFDIR", |env_sysconfdir| {
        Some(join_if_relative(
            &prefix,
            env_sysconfdir.unwrap_or("/etc/".to_owned()),
        ))
    });

    let datadir = overridable_path("DATADIR", |env_datadir| {
        env_datadir.map(|p| join_if_relative(&prefix, p))
    });
    overridable_path("BINDIR", |env_bindir| {
        env_bindir.map(|p| join_if_relative(&prefix, p))
    });
    overridable_path("DOCDIR", |env_docdir| {
        env_docdir.map(|p| {
            join_if_relative(
                &datadir
                    .expect("Setting DOCDIR without setting DATADIR is not currently supported"),
                p,
            )
        })
    });
}

fn get_version() -> String {
    use std::process::Command;
    String::from_utf8(
        Command::new("build_tools/git_version_gen.sh")
            .output()
            .unwrap()
            .stdout,
    )
    .unwrap()
    .trim_ascii_end()
    .to_owned()
}