src/bootstrap/util.rs - toolchain/rustc - Git at Google

 //! Various utility functions used throughout rustbuild.
 //!
 //! Simple things like testing the various filesystem operations here and there,
 //! not a lot of interesting happenings here unfortunately.

 use build_helper::util::{fail, try_run};
 use std::env;
 use std::fs;
 use std::io;
 use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 use std::str;
 use std::time::{Instant, SystemTime, UNIX_EPOCH};

 use crate::builder::Builder;
 use crate::config::{Config, TargetSelection};
 use crate::OnceCell;

 /// A helper macro to `unwrap` a result except also print out details like:
 ///
 /// * The file/line of the panic
 /// * The expression that failed
 /// * The error itself
 ///
 /// This is currently used judiciously throughout the build system rather than
 /// using a `Result` with `try!`, but this may change one day...
 #[macro_export]
 macro_rules! t {
     ($e:expr) => {
         match $e {
             Ok(e) => e,
             Err(e) => panic!("{} failed with {}", stringify!($e), e),
         }
     };
     // it can show extra info in the second parameter
     ($e:expr, $extra:expr) => {
         match $e {
             Ok(e) => e,
             Err(e) => panic!("{} failed with {} ({:?})", stringify!($e), e, $extra),
         }
     };
 }
 pub use t;

 /// Given an executable called `name`, return the filename for the
 /// executable for a particular target.
 pub fn exe(name: &str, target: TargetSelection) -> String {
     if target.contains("windows") {
         format!("{name}.exe")
     } else if target.contains("uefi") {
         format!("{name}.efi")
     } else {
         name.to_string()
     }
 }

 /// Returns `true` if the file name given looks like a dynamic library.
 pub fn is_dylib(name: &str) -> bool {
     name.ends_with(".dylib") || name.ends_with(".so") || name.ends_with(".dll")
 }

 /// Returns `true` if the file name given looks like a debug info file
 pub fn is_debug_info(name: &str) -> bool {
     // FIXME: consider split debug info on other platforms (e.g., Linux, macOS)
     name.ends_with(".pdb")
 }

 /// Returns the corresponding relative library directory that the compiler's
 /// dylibs will be found in.
 pub fn libdir(target: TargetSelection) -> &'static str {
     if target.contains("windows") { "bin" } else { "lib" }
 }

 /// Adds a list of lookup paths to `cmd`'s dynamic library lookup path.
 /// If the dylib_path_var is already set for this cmd, the old value will be overwritten!
 pub fn add_dylib_path(path: Vec<PathBuf>, cmd: &mut Command) {
     let mut list = dylib_path();
     for path in path {
         list.insert(0, path);
     }
     cmd.env(dylib_path_var(), t!(env::join_paths(list)));
 }

 include!("dylib_util.rs");

 /// Adds a list of lookup paths to `cmd`'s link library lookup path.
 pub fn add_link_lib_path(path: Vec<PathBuf>, cmd: &mut Command) {
     let mut list = link_lib_path();
     for path in path {
         list.insert(0, path);
     }
     cmd.env(link_lib_path_var(), t!(env::join_paths(list)));
 }

 /// Returns the environment variable which the link library lookup path
 /// resides in for this platform.
 fn link_lib_path_var() -> &'static str {
     if cfg!(target_env = "msvc") { "LIB" } else { "LIBRARY_PATH" }
 }

 /// Parses the `link_lib_path_var()` environment variable, returning a list of
 /// paths that are members of this lookup path.
 fn link_lib_path() -> Vec<PathBuf> {
     let var = match env::var_os(link_lib_path_var()) {
         Some(v) => v,
         None => return vec![],
     };
     env::split_paths(&var).collect()
 }

 pub struct TimeIt(bool, Instant);

 /// Returns an RAII structure that prints out how long it took to drop.
 pub fn timeit(builder: &Builder<'_>) -> TimeIt {
     TimeIt(builder.config.dry_run(), Instant::now())
 }

 impl Drop for TimeIt {
     fn drop(&mut self) {
         let time = self.1.elapsed();
         if !self.0 {
             println!("\tfinished in {}.{:03} seconds", time.as_secs(), time.subsec_millis());
         }
     }
 }

 /// Used for download caching
 pub(crate) fn program_out_of_date(stamp: &Path, key: &str) -> bool {
     if !stamp.exists() {
         return true;
     }
     t!(fs::read_to_string(stamp)) != key
 }

 /// Symlinks two directories, using junctions on Windows and normal symlinks on
 /// Unix.
 pub fn symlink_dir(config: &Config, original: &Path, link: &Path) -> io::Result<()> {
     if config.dry_run() {
         return Ok(());
     }
     let _ = fs::remove_dir(link);
     return symlink_dir_inner(original, link);

     #[cfg(not(windows))]
     fn symlink_dir_inner(original: &Path, link: &Path) -> io::Result<()> {
         use std::os::unix::fs;
         fs::symlink(original, link)
     }

     #[cfg(windows)]
     fn symlink_dir_inner(target: &Path, junction: &Path) -> io::Result<()> {
         junction::create(&target, &junction)
     }
 }

 pub fn forcing_clang_based_tests() -> bool {
     if let Some(var) = env::var_os("RUSTBUILD_FORCE_CLANG_BASED_TESTS") {
         match &var.to_string_lossy().to_lowercase()[..] {
             "1" | "yes" | "on" => true,
             "0" | "no" | "off" => false,
             other => {
                 // Let's make sure typos don't go unnoticed
                 panic!(
                     "Unrecognized option '{other}' set in \
                         RUSTBUILD_FORCE_CLANG_BASED_TESTS"
                 )
             }
         }
     } else {
         false
     }
 }

 pub fn use_host_linker(target: TargetSelection) -> bool {
     // FIXME: this information should be gotten by checking the linker flavor
     // of the rustc target
     !(target.contains("emscripten")
         || target.contains("wasm32")
         || target.contains("nvptx")
         || target.contains("fortanix")
         || target.contains("fuchsia")
         || target.contains("bpf")
         || target.contains("switch"))
 }

 pub fn is_valid_test_suite_arg<'a, P: AsRef<Path>>(
     path: &'a Path,
     suite_path: P,
     builder: &Builder<'_>,
 ) -> Option<&'a str> {
     let suite_path = suite_path.as_ref();
     let path = match path.strip_prefix(".") {
         Ok(p) => p,
         Err(_) => path,
     };
     if !path.starts_with(suite_path) {
         return None;
     }
     let abs_path = builder.src.join(path);
     let exists = abs_path.is_dir() || abs_path.is_file();
     if !exists {
         panic!(
             "Invalid test suite filter \"{}\": file or directory does not exist",
             abs_path.display()
         );
     }
     // Since test suite paths are themselves directories, if we don't
     // specify a directory or file, we'll get an empty string here
     // (the result of the test suite directory without its suite prefix).
     // Therefore, we need to filter these out, as only the first --test-args
     // flag is respected, so providing an empty --test-args conflicts with
     // any following it.
     match path.strip_prefix(suite_path).ok().and_then(|p| p.to_str()) {
         Some(s) if !s.is_empty() => Some(s),
         _ => None,
     }
 }

 pub fn run(cmd: &mut Command, print_cmd_on_fail: bool) {
     if try_run(cmd, print_cmd_on_fail).is_err() {
         crate::exit!(1);
     }
 }

 pub fn check_run(cmd: &mut Command, print_cmd_on_fail: bool) -> bool {
     let status = match cmd.status() {
         Ok(status) => status,
         Err(e) => {
             println!("failed to execute command: {cmd:?}\nerror: {e}");
             return false;
         }
     };
     if !status.success() && print_cmd_on_fail {
         println!(
             "\n\ncommand did not execute successfully: {cmd:?}\n\
              expected success, got: {status}\n\n"
         );
     }
     status.success()
 }

 pub fn run_suppressed(cmd: &mut Command) {
     if !try_run_suppressed(cmd) {
         crate::exit!(1);
     }
 }

 pub fn try_run_suppressed(cmd: &mut Command) -> bool {
     let output = match cmd.output() {
         Ok(status) => status,
         Err(e) => fail(&format!("failed to execute command: {cmd:?}\nerror: {e}")),
     };
     if !output.status.success() {
         println!(
             "\n\ncommand did not execute successfully: {:?}\n\
              expected success, got: {}\n\n\
              stdout ----\n{}\n\
              stderr ----\n{}\n\n",
             cmd,
             output.status,
             String::from_utf8_lossy(&output.stdout),
             String::from_utf8_lossy(&output.stderr)
         );
     }
     output.status.success()
 }

 pub fn make(host: &str) -> PathBuf {
     if host.contains("dragonfly")
         || host.contains("freebsd")
         || host.contains("netbsd")
         || host.contains("openbsd")
     {
         PathBuf::from("gmake")
     } else {
         PathBuf::from("make")
     }
 }

 #[track_caller]
 pub fn output(cmd: &mut Command) -> String {
     let output = match cmd.stderr(Stdio::inherit()).output() {
         Ok(status) => status,
         Err(e) => fail(&format!("failed to execute command: {cmd:?}\nerror: {e}")),
     };
     if !output.status.success() {
         panic!(
             "command did not execute successfully: {:?}\n\
              expected success, got: {}",
             cmd, output.status
         );
     }
     String::from_utf8(output.stdout).unwrap()
 }

 pub fn output_result(cmd: &mut Command) -> Result<String, String> {
     let output = match cmd.stderr(Stdio::inherit()).output() {
         Ok(status) => status,
         Err(e) => return Err(format!("failed to run command: {cmd:?}: {e}")),
     };
     if !output.status.success() {
         return Err(format!(
             "command did not execute successfully: {:?}\n\
              expected success, got: {}\n{}",
             cmd,
             output.status,
             String::from_utf8(output.stderr).map_err(|err| format!("{err:?}"))?
         ));
     }
     Ok(String::from_utf8(output.stdout).map_err(|err| format!("{err:?}"))?)
 }

 /// Returns the last-modified time for `path`, or zero if it doesn't exist.
 pub fn mtime(path: &Path) -> SystemTime {
     fs::metadata(path).and_then(|f| f.modified()).unwrap_or(UNIX_EPOCH)
 }

 /// Returns `true` if `dst` is up to date given that the file or files in `src`
 /// are used to generate it.
 ///
 /// Uses last-modified time checks to verify this.
 pub fn up_to_date(src: &Path, dst: &Path) -> bool {
     if !dst.exists() {
         return false;
     }
     let threshold = mtime(dst);
     let meta = match fs::metadata(src) {
         Ok(meta) => meta,
         Err(e) => panic!("source {src:?} failed to get metadata: {e}"),
     };
     if meta.is_dir() {
         dir_up_to_date(src, threshold)
     } else {
         meta.modified().unwrap_or(UNIX_EPOCH) <= threshold
     }
 }

 fn dir_up_to_date(src: &Path, threshold: SystemTime) -> bool {
     t!(fs::read_dir(src)).map(|e| t!(e)).all(|e| {
         let meta = t!(e.metadata());
         if meta.is_dir() {
             dir_up_to_date(&e.path(), threshold)
         } else {
             meta.modified().unwrap_or(UNIX_EPOCH) < threshold
         }
     })
 }

 /// Copied from `std::path::absolute` until it stabilizes.
 ///
 /// FIXME: this shouldn't exist.
 pub(crate) fn absolute(path: &Path) -> PathBuf {
     if path.as_os_str().is_empty() {
         panic!("can't make empty path absolute");
     }
     #[cfg(unix)]
     {
         t!(absolute_unix(path), format!("could not make path absolute: {}", path.display()))
     }
     #[cfg(windows)]
     {
         t!(absolute_windows(path), format!("could not make path absolute: {}", path.display()))
     }
     #[cfg(not(any(unix, windows)))]
     {
         println!("warning: bootstrap is not supported on non-unix platforms");
         t!(std::fs::canonicalize(t!(std::env::current_dir()))).join(path)
     }
 }

 #[cfg(unix)]
 /// Make a POSIX path absolute without changing its semantics.
 fn absolute_unix(path: &Path) -> io::Result<PathBuf> {
     // This is mostly a wrapper around collecting `Path::components`, with
     // exceptions made where this conflicts with the POSIX specification.
     // See 4.13 Pathname Resolution, IEEE Std 1003.1-2017
     // https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13

     use std::os::unix::prelude::OsStrExt;
     let mut components = path.components();
     let path_os = path.as_os_str().as_bytes();

     let mut normalized = if path.is_absolute() {
         // "If a pathname begins with two successive <slash> characters, the
         // first component following the leading <slash> characters may be
         // interpreted in an implementation-defined manner, although more than
         // two leading <slash> characters shall be treated as a single <slash>
         // character."
         if path_os.starts_with(b"//") && !path_os.starts_with(b"///") {
             components.next();
             PathBuf::from("//")
         } else {
             PathBuf::new()
         }
     } else {
         env::current_dir()?
     };
     normalized.extend(components);

     // "Interfaces using pathname resolution may specify additional constraints
     // when a pathname that does not name an existing directory contains at
     // least one non- <slash> character and contains one or more trailing
     // <slash> characters".
     // A trailing <slash> is also meaningful if "a symbolic link is
     // encountered during pathname resolution".

     if path_os.ends_with(b"/") {
         normalized.push("");
     }

     Ok(normalized)
 }

 #[cfg(windows)]
 fn absolute_windows(path: &std::path::Path) -> std::io::Result<std::path::PathBuf> {
     use std::ffi::OsString;
     use std::io::Error;
     use std::os::windows::ffi::{OsStrExt, OsStringExt};
     use std::ptr::null_mut;
     #[link(name = "kernel32")]
     extern "system" {
         fn GetFullPathNameW(
             lpFileName: *const u16,
             nBufferLength: u32,
             lpBuffer: *mut u16,
             lpFilePart: *mut *const u16,
         ) -> u32;
     }

     unsafe {
         // encode the path as UTF-16
         let path: Vec<u16> = path.as_os_str().encode_wide().chain([0]).collect();
         let mut buffer = Vec::new();
         // Loop until either success or failure.
         loop {
             // Try to get the absolute path
             let len = GetFullPathNameW(
                 path.as_ptr(),
                 buffer.len().try_into().unwrap(),
                 buffer.as_mut_ptr(),
                 null_mut(),
             );
             match len as usize {
                 // Failure
                 0 => return Err(Error::last_os_error()),
                 // Buffer is too small, resize.
                 len if len > buffer.len() => buffer.resize(len, 0),
                 // Success!
                 len => {
                     buffer.truncate(len);
                     return Ok(OsString::from_wide(&buffer).into());
                 }
             }
         }
     }
 }

 /// Adapted from <https://github.com/llvm/llvm-project/blob/782e91224601e461c019e0a4573bbccc6094fbcd/llvm/cmake/modules/HandleLLVMOptions.cmake#L1058-L1079>
 ///
 /// When `clang-cl` is used with instrumentation, we need to add clang's runtime library resource
 /// directory to the linker flags, otherwise there will be linker errors about the profiler runtime
 /// missing. This function returns the path to that directory.
 pub fn get_clang_cl_resource_dir(clang_cl_path: &str) -> PathBuf {
     // Similar to how LLVM does it, to find clang's library runtime directory:
     // - we ask `clang-cl` to locate the `clang_rt.builtins` lib.
     let mut builtins_locator = Command::new(clang_cl_path);
     builtins_locator.args(&["/clang:-print-libgcc-file-name", "/clang:--rtlib=compiler-rt"]);

     let clang_rt_builtins = output(&mut builtins_locator);
     let clang_rt_builtins = Path::new(clang_rt_builtins.trim());
     assert!(
         clang_rt_builtins.exists(),
         "`clang-cl` must correctly locate the library runtime directory"
     );

     // - the profiler runtime will be located in the same directory as the builtins lib, like
     // `$LLVM_DISTRO_ROOT/lib/clang/$LLVM_VERSION/lib/windows`.
     let clang_rt_dir = clang_rt_builtins.parent().expect("The clang lib folder should exist");
     clang_rt_dir.to_path_buf()
 }

 pub fn lld_flag_no_threads(is_windows: bool) -> &'static str {
     static LLD_NO_THREADS: OnceCell<(&'static str, &'static str)> = OnceCell::new();
     let (windows, other) = LLD_NO_THREADS.get_or_init(|| {
         let out = output(Command::new("lld").arg("-flavor").arg("ld").arg("--version"));
         let newer = match (out.find(char::is_numeric), out.find('.')) {
             (Some(b), Some(e)) => out.as_str()[b..e].parse::<i32>().ok().unwrap_or(14) > 10,
             _ => true,
         };
         if newer { ("/threads:1", "--threads=1") } else { ("/no-threads", "--no-threads") }
     });
     if is_windows { windows } else { other }
 }

 pub fn dir_is_empty(dir: &Path) -> bool {
     t!(std::fs::read_dir(dir)).next().is_none()
 }
	//! Various utility functions used throughout rustbuild.
	//!
	//! Simple things like testing the various filesystem operations here and there,
	//! not a lot of interesting happenings here unfortunately.

	use build_helper::util::{fail, try_run};
	use std::env;
	use std::fs;
	use std::io;
	use std::path::{Path, PathBuf};
	use std::process::{Command, Stdio};
	use std::str;
	use std::time::{Instant, SystemTime, UNIX_EPOCH};

	use crate::builder::Builder;
	use crate::config::{Config, TargetSelection};
	use crate::OnceCell;

	/// A helper macro to `unwrap` a result except also print out details like:
	///
	/// * The file/line of the panic
	/// * The expression that failed
	/// * The error itself
	///
	/// This is currently used judiciously throughout the build system rather than
	/// using a `Result` with `try!`, but this may change one day...
	#[macro_export]
	macro_rules! t {
	($e:expr) => {
	match $e {
	Ok(e) => e,
	Err(e) => panic!("{} failed with {}", stringify!($e), e),
	}
	};
	// it can show extra info in the second parameter
	($e:expr, $extra:expr) => {
	match $e {
	Ok(e) => e,
	Err(e) => panic!("{} failed with {} ({:?})", stringify!($e), e, $extra),
	}
	};
	}
	pub use t;

	/// Given an executable called `name`, return the filename for the
	/// executable for a particular target.
	pub fn exe(name: &str, target: TargetSelection) -> String {
	if target.contains("windows") {
	format!("{name}.exe")
	} else if target.contains("uefi") {
	format!("{name}.efi")
	} else {
	name.to_string()
	}
	}

	/// Returns `true` if the file name given looks like a dynamic library.
	pub fn is_dylib(name: &str) -> bool {
	name.ends_with(".dylib") \|\| name.ends_with(".so") \|\| name.ends_with(".dll")
	}

	/// Returns `true` if the file name given looks like a debug info file
	pub fn is_debug_info(name: &str) -> bool {
	// FIXME: consider split debug info on other platforms (e.g., Linux, macOS)
	name.ends_with(".pdb")
	}

	/// Returns the corresponding relative library directory that the compiler's
	/// dylibs will be found in.
	pub fn libdir(target: TargetSelection) -> &'static str {
	if target.contains("windows") { "bin" } else { "lib" }
	}

	/// Adds a list of lookup paths to `cmd`'s dynamic library lookup path.
	/// If the dylib_path_var is already set for this cmd, the old value will be overwritten!
	pub fn add_dylib_path(path: Vec<PathBuf>, cmd: &mut Command) {
	let mut list = dylib_path();
	for path in path {
	list.insert(0, path);
	}
	cmd.env(dylib_path_var(), t!(env::join_paths(list)));
	}

	include!("dylib_util.rs");

	/// Adds a list of lookup paths to `cmd`'s link library lookup path.
	pub fn add_link_lib_path(path: Vec<PathBuf>, cmd: &mut Command) {
	let mut list = link_lib_path();
	for path in path {
	list.insert(0, path);
	}
	cmd.env(link_lib_path_var(), t!(env::join_paths(list)));
	}

	/// Returns the environment variable which the link library lookup path
	/// resides in for this platform.
	fn link_lib_path_var() -> &'static str {
	if cfg!(target_env = "msvc") { "LIB" } else { "LIBRARY_PATH" }
	}

	/// Parses the `link_lib_path_var()` environment variable, returning a list of
	/// paths that are members of this lookup path.
	fn link_lib_path() -> Vec<PathBuf> {
	let var = match env::var_os(link_lib_path_var()) {
	Some(v) => v,
	None => return vec![],
	};
	env::split_paths(&var).collect()
	}

	pub struct TimeIt(bool, Instant);

	/// Returns an RAII structure that prints out how long it took to drop.
	pub fn timeit(builder: &Builder<'_>) -> TimeIt {
	TimeIt(builder.config.dry_run(), Instant::now())
	}

	impl Drop for TimeIt {
	fn drop(&mut self) {
	let time = self.1.elapsed();
	if !self.0 {
	println!("\tfinished in {}.{:03} seconds", time.as_secs(), time.subsec_millis());
	}
	}
	}

	/// Used for download caching
	pub(crate) fn program_out_of_date(stamp: &Path, key: &str) -> bool {
	if !stamp.exists() {
	return true;
	}
	t!(fs::read_to_string(stamp)) != key
	}

	/// Symlinks two directories, using junctions on Windows and normal symlinks on
	/// Unix.
	pub fn symlink_dir(config: &Config, original: &Path, link: &Path) -> io::Result<()> {
	if config.dry_run() {
	return Ok(());
	}
	let _ = fs::remove_dir(link);
	return symlink_dir_inner(original, link);

	#[cfg(not(windows))]
	fn symlink_dir_inner(original: &Path, link: &Path) -> io::Result<()> {
	use std::os::unix::fs;
	fs::symlink(original, link)
	}

	#[cfg(windows)]
	fn symlink_dir_inner(target: &Path, junction: &Path) -> io::Result<()> {
	junction::create(&target, &junction)
	}
	}

	pub fn forcing_clang_based_tests() -> bool {
	if let Some(var) = env::var_os("RUSTBUILD_FORCE_CLANG_BASED_TESTS") {
	match &var.to_string_lossy().to_lowercase()[..] {
	"1" \| "yes" \| "on" => true,
	"0" \| "no" \| "off" => false,
	other => {
	// Let's make sure typos don't go unnoticed
	panic!(
	"Unrecognized option '{other}' set in \
	RUSTBUILD_FORCE_CLANG_BASED_TESTS"
	)
	}
	}
	} else {
	false
	}
	}

	pub fn use_host_linker(target: TargetSelection) -> bool {
	// FIXME: this information should be gotten by checking the linker flavor
	// of the rustc target
	!(target.contains("emscripten")
	\|\| target.contains("wasm32")
	\|\| target.contains("nvptx")
	\|\| target.contains("fortanix")
	\|\| target.contains("fuchsia")
	\|\| target.contains("bpf")
	\|\| target.contains("switch"))
	}

	pub fn is_valid_test_suite_arg<'a, P: AsRef<Path>>(
	path: &'a Path,
	suite_path: P,
	builder: &Builder<'_>,
	) -> Option<&'a str> {
	let suite_path = suite_path.as_ref();
	let path = match path.strip_prefix(".") {
	Ok(p) => p,
	Err(_) => path,
	};
	if !path.starts_with(suite_path) {
	return None;
	}
	let abs_path = builder.src.join(path);
	let exists = abs_path.is_dir() \|\| abs_path.is_file();
	if !exists {
	panic!(
	"Invalid test suite filter \"{}\": file or directory does not exist",
	abs_path.display()
	);
	}
	// Since test suite paths are themselves directories, if we don't
	// specify a directory or file, we'll get an empty string here
	// (the result of the test suite directory without its suite prefix).
	// Therefore, we need to filter these out, as only the first --test-args
	// flag is respected, so providing an empty --test-args conflicts with
	// any following it.
	match path.strip_prefix(suite_path).ok().and_then(\|p\| p.to_str()) {
	Some(s) if !s.is_empty() => Some(s),
	_ => None,
	}
	}

	pub fn run(cmd: &mut Command, print_cmd_on_fail: bool) {
	if try_run(cmd, print_cmd_on_fail).is_err() {
	crate::exit!(1);
	}
	}

	pub fn check_run(cmd: &mut Command, print_cmd_on_fail: bool) -> bool {
	let status = match cmd.status() {
	Ok(status) => status,
	Err(e) => {
	println!("failed to execute command: {cmd:?}\nerror: {e}");
	return false;
	}
	};
	if !status.success() && print_cmd_on_fail {
	println!(
	"\n\ncommand did not execute successfully: {cmd:?}\n\
	expected success, got: {status}\n\n"
	);
	}
	status.success()
	}

	pub fn run_suppressed(cmd: &mut Command) {
	if !try_run_suppressed(cmd) {
	crate::exit!(1);
	}
	}

	pub fn try_run_suppressed(cmd: &mut Command) -> bool {
	let output = match cmd.output() {
	Ok(status) => status,
	Err(e) => fail(&format!("failed to execute command: {cmd:?}\nerror: {e}")),
	};
	if !output.status.success() {
	println!(
	"\n\ncommand did not execute successfully: {:?}\n\
	expected success, got: {}\n\n\
	stdout ----\n{}\n\
	stderr ----\n{}\n\n",
	cmd,
	output.status,
	String::from_utf8_lossy(&output.stdout),
	String::from_utf8_lossy(&output.stderr)
	);
	}
	output.status.success()
	}

	pub fn make(host: &str) -> PathBuf {
	if host.contains("dragonfly")
	\|\| host.contains("freebsd")
	\|\| host.contains("netbsd")
	\|\| host.contains("openbsd")
	{
	PathBuf::from("gmake")
	} else {
	PathBuf::from("make")
	}
	}

	#[track_caller]
	pub fn output(cmd: &mut Command) -> String {
	let output = match cmd.stderr(Stdio::inherit()).output() {
	Ok(status) => status,
	Err(e) => fail(&format!("failed to execute command: {cmd:?}\nerror: {e}")),
	};
	if !output.status.success() {
	panic!(
	"command did not execute successfully: {:?}\n\
	expected success, got: {}",
	cmd, output.status
	);
	}
	String::from_utf8(output.stdout).unwrap()
	}

	pub fn output_result(cmd: &mut Command) -> Result<String, String> {
	let output = match cmd.stderr(Stdio::inherit()).output() {
	Ok(status) => status,
	Err(e) => return Err(format!("failed to run command: {cmd:?}: {e}")),
	};
	if !output.status.success() {
	return Err(format!(
	"command did not execute successfully: {:?}\n\
	expected success, got: {}\n{}",
	cmd,
	output.status,
	String::from_utf8(output.stderr).map_err(\|err\| format!("{err:?}"))?
	));
	}
	Ok(String::from_utf8(output.stdout).map_err(\|err\| format!("{err:?}"))?)
	}

	/// Returns the last-modified time for `path`, or zero if it doesn't exist.
	pub fn mtime(path: &Path) -> SystemTime {
	fs::metadata(path).and_then(\|f\| f.modified()).unwrap_or(UNIX_EPOCH)
	}

	/// Returns `true` if `dst` is up to date given that the file or files in `src`
	/// are used to generate it.
	///
	/// Uses last-modified time checks to verify this.
	pub fn up_to_date(src: &Path, dst: &Path) -> bool {
	if !dst.exists() {
	return false;
	}
	let threshold = mtime(dst);
	let meta = match fs::metadata(src) {
	Ok(meta) => meta,
	Err(e) => panic!("source {src:?} failed to get metadata: {e}"),
	};
	if meta.is_dir() {
	dir_up_to_date(src, threshold)
	} else {
	meta.modified().unwrap_or(UNIX_EPOCH) <= threshold
	}
	}

	fn dir_up_to_date(src: &Path, threshold: SystemTime) -> bool {
	t!(fs::read_dir(src)).map(\|e\| t!(e)).all(\|e\| {
	let meta = t!(e.metadata());
	if meta.is_dir() {
	dir_up_to_date(&e.path(), threshold)
	} else {
	meta.modified().unwrap_or(UNIX_EPOCH) < threshold
	}
	})
	}

	/// Copied from `std::path::absolute` until it stabilizes.
	///
	/// FIXME: this shouldn't exist.
	pub(crate) fn absolute(path: &Path) -> PathBuf {
	if path.as_os_str().is_empty() {
	panic!("can't make empty path absolute");
	}
	#[cfg(unix)]
	{
	t!(absolute_unix(path), format!("could not make path absolute: {}", path.display()))
	}
	#[cfg(windows)]
	{
	t!(absolute_windows(path), format!("could not make path absolute: {}", path.display()))
	}
	#[cfg(not(any(unix, windows)))]
	{
	println!("warning: bootstrap is not supported on non-unix platforms");
	t!(std::fs::canonicalize(t!(std::env::current_dir()))).join(path)
	}
	}

	#[cfg(unix)]
	/// Make a POSIX path absolute without changing its semantics.
	fn absolute_unix(path: &Path) -> io::Result<PathBuf> {
	// This is mostly a wrapper around collecting `Path::components`, with
	// exceptions made where this conflicts with the POSIX specification.
	// See 4.13 Pathname Resolution, IEEE Std 1003.1-2017
	// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13

	use std::os::unix::prelude::OsStrExt;
	let mut components = path.components();
	let path_os = path.as_os_str().as_bytes();

	let mut normalized = if path.is_absolute() {
	// "If a pathname begins with two successive <slash> characters, the
	// first component following the leading <slash> characters may be
	// interpreted in an implementation-defined manner, although more than
	// two leading <slash> characters shall be treated as a single <slash>
	// character."
	if path_os.starts_with(b"//") && !path_os.starts_with(b"///") {
	components.next();
	PathBuf::from("//")
	} else {
	PathBuf::new()
	}
	} else {
	env::current_dir()?
	};
	normalized.extend(components);

	// "Interfaces using pathname resolution may specify additional constraints
	// when a pathname that does not name an existing directory contains at
	// least one non- <slash> character and contains one or more trailing
	// <slash> characters".
	// A trailing <slash> is also meaningful if "a symbolic link is
	// encountered during pathname resolution".

	if path_os.ends_with(b"/") {
	normalized.push("");
	}

	Ok(normalized)
	}

	#[cfg(windows)]
	fn absolute_windows(path: &std::path::Path) -> std::io::Result<std::path::PathBuf> {
	use std::ffi::OsString;
	use std::io::Error;
	use std::os::windows::ffi::{OsStrExt, OsStringExt};
	use std::ptr::null_mut;
	#[link(name = "kernel32")]
	extern "system" {
	fn GetFullPathNameW(
	lpFileName: *const u16,
	nBufferLength: u32,
	lpBuffer: *mut u16,
	lpFilePart: mut const u16,
	) -> u32;
	}

	unsafe {
	// encode the path as UTF-16
	let path: Vec<u16> = path.as_os_str().encode_wide().chain([0]).collect();
	let mut buffer = Vec::new();
	// Loop until either success or failure.
	loop {
	// Try to get the absolute path
	let len = GetFullPathNameW(
	path.as_ptr(),
	buffer.len().try_into().unwrap(),
	buffer.as_mut_ptr(),
	null_mut(),
	);
	match len as usize {
	// Failure
	0 => return Err(Error::last_os_error()),
	// Buffer is too small, resize.
	len if len > buffer.len() => buffer.resize(len, 0),
	// Success!
	len => {
	buffer.truncate(len);
	return Ok(OsString::from_wide(&buffer).into());
	}
	}
	}
	}
	}

	/// Adapted from <https://github.com/llvm/llvm-project/blob/782e91224601e461c019e0a4573bbccc6094fbcd/llvm/cmake/modules/HandleLLVMOptions.cmake#L1058-L1079>
	///
	/// When `clang-cl` is used with instrumentation, we need to add clang's runtime library resource
	/// directory to the linker flags, otherwise there will be linker errors about the profiler runtime
	/// missing. This function returns the path to that directory.
	pub fn get_clang_cl_resource_dir(clang_cl_path: &str) -> PathBuf {
	// Similar to how LLVM does it, to find clang's library runtime directory:
	// - we ask `clang-cl` to locate the `clang_rt.builtins` lib.
	let mut builtins_locator = Command::new(clang_cl_path);
	builtins_locator.args(&["/clang:-print-libgcc-file-name", "/clang:--rtlib=compiler-rt"]);

	let clang_rt_builtins = output(&mut builtins_locator);
	let clang_rt_builtins = Path::new(clang_rt_builtins.trim());
	assert!(
	clang_rt_builtins.exists(),
	"`clang-cl` must correctly locate the library runtime directory"
	);

	// - the profiler runtime will be located in the same directory as the builtins lib, like
	// `$LLVM_DISTRO_ROOT/lib/clang/$LLVM_VERSION/lib/windows`.
	let clang_rt_dir = clang_rt_builtins.parent().expect("The clang lib folder should exist");
	clang_rt_dir.to_path_buf()
	}

	pub fn lld_flag_no_threads(is_windows: bool) -> &'static str {
	static LLD_NO_THREADS: OnceCell<(&'static str, &'static str)> = OnceCell::new();
	let (windows, other) = LLD_NO_THREADS.get_or_init(\|\| {
	let out = output(Command::new("lld").arg("-flavor").arg("ld").arg("--version"));
	let newer = match (out.find(char::is_numeric), out.find('.')) {
	(Some(b), Some(e)) => out.as_str()[b..e].parse::<i32>().ok().unwrap_or(14) > 10,
	_ => true,
	};
	if newer { ("/threads:1", "--threads=1") } else { ("/no-threads", "--no-threads") }
	});
	if is_windows { windows } else { other }
	}

	pub fn dir_is_empty(dir: &Path) -> bool {
	t!(std::fs::read_dir(dir)).next().is_none()
	}