library/std/src/sys/pal/unix/mod.rs - third_party/rust - Git at Google

 #![allow(missing_docs, nonstandard_style)]

 use crate::io::ErrorKind;

 #[cfg(not(target_os = "espidf"))]
 #[macro_use]
 pub mod weak;

 #[cfg(target_os = "fuchsia")]
 pub mod fuchsia;
 pub mod futex;
 #[cfg(any(target_os = "linux", target_os = "android"))]
 pub mod kernel_copy;
 #[cfg(target_os = "linux")]
 pub mod linux;
 pub mod os;
 pub mod pipe;
 pub mod stack_overflow;
 pub mod sync;
 pub mod thread;
 pub mod thread_parking;
 pub mod time;

 #[cfg(target_os = "espidf")]
 pub fn init(_argc: isize, _argv: *const *const u8, _sigpipe: u8) {}

 #[cfg(not(target_os = "espidf"))]
 #[cfg_attr(target_os = "vita", allow(unused_variables))]
 // SAFETY: must be called only once during runtime initialization.
 // NOTE: this is not guaranteed to run, for example when Rust code is called externally.
 // See `fn init()` in `library/std/src/rt.rs` for docs on `sigpipe`.
 pub unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) {
     // The standard streams might be closed on application startup. To prevent
     // std::io::{stdin, stdout,stderr} objects from using other unrelated file
     // resources opened later, we reopen standards streams when they are closed.
     sanitize_standard_fds();

     // By default, some platforms will send a *signal* when an EPIPE error
     // would otherwise be delivered. This runtime doesn't install a SIGPIPE
     // handler, causing it to kill the program, which isn't exactly what we
     // want!
     //
     // Hence, we set SIGPIPE to ignore when the program starts up in order
     // to prevent this problem. Use `-Zon-broken-pipe=...` to alter this
     // behavior.
     reset_sigpipe(sigpipe);

     stack_overflow::init();
     #[cfg(not(target_os = "vita"))]
     crate::sys::args::init(argc, argv);

     // Normally, `thread::spawn` will call `Thread::set_name` but since this thread
     // already exists, we have to call it ourselves. We only do this on Apple targets
     // because some unix-like operating systems such as Linux share process-id and
     // thread-id for the main thread and so renaming the main thread will rename the
     // process and we only want to enable this on platforms we've tested.
     if cfg!(target_vendor = "apple") {
         thread::Thread::set_name(&c"main");
     }

     unsafe fn sanitize_standard_fds() {
         // fast path with a single syscall for systems with poll()
         #[cfg(not(any(
             miri,
             target_os = "emscripten",
             target_os = "fuchsia",
             target_os = "vxworks",
             target_os = "redox",
             target_os = "l4re",
             target_os = "horizon",
             target_os = "vita",
             target_os = "rtems",
             // The poll on Darwin doesn't set POLLNVAL for closed fds.
             target_vendor = "apple",
         )))]
         'poll: {
             #[cfg(not(all(target_os = "linux", target_env = "gnu")))]
             use libc::open as open64;
             #[cfg(all(target_os = "linux", target_env = "gnu"))]
             use libc::open64;

             use crate::sys::os::errno;
             let pfds: &mut [_] = &mut [
                 libc::pollfd { fd: 0, events: 0, revents: 0 },
                 libc::pollfd { fd: 1, events: 0, revents: 0 },
                 libc::pollfd { fd: 2, events: 0, revents: 0 },
             ];

             while libc::poll(pfds.as_mut_ptr(), 3, 0) == -1 {
                 match errno() {
                     libc::EINTR => continue,
                     #[cfg(target_vendor = "unikraft")]
                     libc::ENOSYS => {
                         // Not all configurations of Unikraft enable `LIBPOSIX_EVENT`.
                         break 'poll;
                     }
                     libc::EINVAL | libc::EAGAIN | libc::ENOMEM => {
                         // RLIMIT_NOFILE or temporary allocation failures
                         // may be preventing use of poll(), fall back to fcntl
                         break 'poll;
                     }
                     _ => libc::abort(),
                 }
             }
             for pfd in pfds {
                 if pfd.revents & libc::POLLNVAL == 0 {
                     continue;
                 }
                 if open64(c"/dev/null".as_ptr(), libc::O_RDWR, 0) == -1 {
                     // If the stream is closed but we failed to reopen it, abort the
                     // process. Otherwise we wouldn't preserve the safety of
                     // operations on the corresponding Rust object Stdin, Stdout, or
                     // Stderr.
                     libc::abort();
                 }
             }
             return;
         }

         // fallback in case poll isn't available or limited by RLIMIT_NOFILE
         #[cfg(not(any(
             // The standard fds are always available in Miri.
             miri,
             target_os = "emscripten",
             target_os = "fuchsia",
             target_os = "vxworks",
             target_os = "l4re",
             target_os = "horizon",
             target_os = "vita",
         )))]
         {
             #[cfg(not(all(target_os = "linux", target_env = "gnu")))]
             use libc::open as open64;
             #[cfg(all(target_os = "linux", target_env = "gnu"))]
             use libc::open64;

             use crate::sys::os::errno;
             for fd in 0..3 {
                 if libc::fcntl(fd, libc::F_GETFD) == -1 && errno() == libc::EBADF {
                     if open64(c"/dev/null".as_ptr(), libc::O_RDWR, 0) == -1 {
                         // If the stream is closed but we failed to reopen it, abort the
                         // process. Otherwise we wouldn't preserve the safety of
                         // operations on the corresponding Rust object Stdin, Stdout, or
                         // Stderr.
                         libc::abort();
                     }
                 }
             }
         }
     }

     unsafe fn reset_sigpipe(#[allow(unused_variables)] sigpipe: u8) {
         #[cfg(not(any(
             target_os = "emscripten",
             target_os = "fuchsia",
             target_os = "horizon",
             target_os = "vxworks",
             target_os = "vita",
             // Unikraft's `signal` implementation is currently broken:
             // https://github.com/unikraft/lib-musl/issues/57
             target_vendor = "unikraft",
         )))]
         {
             // We don't want to add this as a public type to std, nor do we
             // want to `include!` a file from the compiler (which would break
             // Miri and xargo for example), so we choose to duplicate these
             // constants from `compiler/rustc_session/src/config/sigpipe.rs`.
             // See the other file for docs. NOTE: Make sure to keep them in
             // sync!
             mod sigpipe {
                 pub const DEFAULT: u8 = 0;
                 pub const INHERIT: u8 = 1;
                 pub const SIG_IGN: u8 = 2;
                 pub const SIG_DFL: u8 = 3;
             }

             let (sigpipe_attr_specified, handler) = match sigpipe {
                 sigpipe::DEFAULT => (false, Some(libc::SIG_IGN)),
                 sigpipe::INHERIT => (true, None),
                 sigpipe::SIG_IGN => (true, Some(libc::SIG_IGN)),
                 sigpipe::SIG_DFL => (true, Some(libc::SIG_DFL)),
                 _ => unreachable!(),
             };
             if sigpipe_attr_specified {
                 ON_BROKEN_PIPE_FLAG_USED.store(true, crate::sync::atomic::Ordering::Relaxed);
             }
             if let Some(handler) = handler {
                 rtassert!(signal(libc::SIGPIPE, handler) != libc::SIG_ERR);
                 #[cfg(target_os = "hurd")]
                 {
                     rtassert!(signal(libc::SIGLOST, handler) != libc::SIG_ERR);
                 }
             }
         }
     }
 }

 // This is set (up to once) in reset_sigpipe.
 #[cfg(not(any(
     target_os = "espidf",
     target_os = "emscripten",
     target_os = "fuchsia",
     target_os = "horizon",
     target_os = "vxworks",
     target_os = "vita",
 )))]
 static ON_BROKEN_PIPE_FLAG_USED: crate::sync::atomic::AtomicBool =
     crate::sync::atomic::AtomicBool::new(false);

 #[cfg(not(any(
     target_os = "espidf",
     target_os = "emscripten",
     target_os = "fuchsia",
     target_os = "horizon",
     target_os = "vxworks",
     target_os = "vita",
     target_os = "nuttx",
 )))]
 pub(crate) fn on_broken_pipe_flag_used() -> bool {
     ON_BROKEN_PIPE_FLAG_USED.load(crate::sync::atomic::Ordering::Relaxed)
 }

 // SAFETY: must be called only once during runtime cleanup.
 // NOTE: this is not guaranteed to run, for example when the program aborts.
 pub unsafe fn cleanup() {
     stack_overflow::cleanup();
 }

 #[allow(unused_imports)]
 pub use libc::signal;

 #[inline]
 pub(crate) fn is_interrupted(errno: i32) -> bool {
     errno == libc::EINTR
 }

 pub fn decode_error_kind(errno: i32) -> ErrorKind {
     use ErrorKind::*;
     match errno as libc::c_int {
         libc::E2BIG => ArgumentListTooLong,
         libc::EADDRINUSE => AddrInUse,
         libc::EADDRNOTAVAIL => AddrNotAvailable,
         libc::EBUSY => ResourceBusy,
         libc::ECONNABORTED => ConnectionAborted,
         libc::ECONNREFUSED => ConnectionRefused,
         libc::ECONNRESET => ConnectionReset,
         libc::EDEADLK => Deadlock,
         libc::EDQUOT => QuotaExceeded,
         libc::EEXIST => AlreadyExists,
         libc::EFBIG => FileTooLarge,
         libc::EHOSTUNREACH => HostUnreachable,
         libc::EINTR => Interrupted,
         libc::EINVAL => InvalidInput,
         libc::EISDIR => IsADirectory,
         libc::ELOOP => FilesystemLoop,
         libc::ENOENT => NotFound,
         libc::ENOMEM => OutOfMemory,
         libc::ENOSPC => StorageFull,
         libc::ENOSYS => Unsupported,
         libc::EMLINK => TooManyLinks,
         libc::ENAMETOOLONG => InvalidFilename,
         libc::ENETDOWN => NetworkDown,
         libc::ENETUNREACH => NetworkUnreachable,
         libc::ENOTCONN => NotConnected,
         libc::ENOTDIR => NotADirectory,
         #[cfg(not(target_os = "aix"))]
         libc::ENOTEMPTY => DirectoryNotEmpty,
         libc::EPIPE => BrokenPipe,
         libc::EROFS => ReadOnlyFilesystem,
         libc::ESPIPE => NotSeekable,
         libc::ESTALE => StaleNetworkFileHandle,
         libc::ETIMEDOUT => TimedOut,
         libc::ETXTBSY => ExecutableFileBusy,
         libc::EXDEV => CrossesDevices,
         libc::EINPROGRESS => InProgress,
         libc::EOPNOTSUPP => Unsupported,

         libc::EACCES | libc::EPERM => PermissionDenied,

         // These two constants can have the same value on some systems,
         // but different values on others, so we can't use a match
         // clause
         x if x == libc::EAGAIN || x == libc::EWOULDBLOCK => WouldBlock,

         _ => Uncategorized,
     }
 }

 #[doc(hidden)]
 pub trait IsMinusOne {
     fn is_minus_one(&self) -> bool;
 }

 macro_rules! impl_is_minus_one {
     ($($t:ident)*) => ($(impl IsMinusOne for $t {
         fn is_minus_one(&self) -> bool {
             *self == -1
         }
     })*)
 }

 impl_is_minus_one! { i8 i16 i32 i64 isize }

 /// Converts native return values to Result using the *-1 means error is in `errno`*  convention.
 /// Non-error values are `Ok`-wrapped.
 pub fn cvt<T: IsMinusOne>(t: T) -> crate::io::Result<T> {
     if t.is_minus_one() { Err(crate::io::Error::last_os_error()) } else { Ok(t) }
 }

 /// `-1` → look at `errno` → retry on `EINTR`. Otherwise `Ok()`-wrap the closure return value.
 pub fn cvt_r<T, F>(mut f: F) -> crate::io::Result<T>
 where
     T: IsMinusOne,
     F: FnMut() -> T,
 {
     loop {
         match cvt(f()) {
             Err(ref e) if e.is_interrupted() => {}
             other => return other,
         }
     }
 }

 #[allow(dead_code)] // Not used on all platforms.
 /// Zero means `Ok()`, all other values are treated as raw OS errors. Does not look at `errno`.
 pub fn cvt_nz(error: libc::c_int) -> crate::io::Result<()> {
     if error == 0 { Ok(()) } else { Err(crate::io::Error::from_raw_os_error(error)) }
 }

 // libc::abort() will run the SIGABRT handler.  That's fine because anyone who
 // installs a SIGABRT handler already has to expect it to run in Very Bad
 // situations (eg, malloc crashing).
 //
 // Current glibc's abort() function unblocks SIGABRT, raises SIGABRT, clears the
 // SIGABRT handler and raises it again, and then starts to get creative.
 //
 // See the public documentation for `intrinsics::abort()` and `process::abort()`
 // for further discussion.
 //
 // There is confusion about whether libc::abort() flushes stdio streams.
 // libc::abort() is required by ISO C 99 (7.14.1.1p5) to be async-signal-safe,
 // so flushing streams is at least extremely hard, if not entirely impossible.
 //
 // However, some versions of POSIX (eg IEEE Std 1003.1-2001) required abort to
 // do so.  In 1003.1-2004 this was fixed.
 //
 // glibc's implementation did the flush, unsafely, before glibc commit
 // 91e7cf982d01 `abort: Do not flush stdio streams [BZ #15436]` by Florian
 // Weimer.  According to glibc's NEWS:
 //
 //    The abort function terminates the process immediately, without flushing
 //    stdio streams.  Previous glibc versions used to flush streams, resulting
 //    in deadlocks and further data corruption.  This change also affects
 //    process aborts as the result of assertion failures.
 //
 // This is an accurate description of the problem.  The only solution for
 // program with nontrivial use of C stdio is a fixed libc - one which does not
 // try to flush in abort - since even libc-internal errors, and assertion
 // failures generated from C, will go via abort().
 //
 // On systems with old, buggy, libcs, the impact can be severe for a
 // multithreaded C program.  It is much less severe for Rust, because Rust
 // stdlib doesn't use libc stdio buffering.  In a typical Rust program, which
 // does not use C stdio, even a buggy libc::abort() is, in fact, safe.
 pub fn abort_internal() -> ! {
     unsafe { libc::abort() }
 }

 cfg_if::cfg_if! {
     if #[cfg(target_os = "android")] {
         #[link(name = "dl", kind = "static", modifiers = "-bundle",
             cfg(target_feature = "crt-static"))]
         #[link(name = "dl", cfg(not(target_feature = "crt-static")))]
         #[link(name = "log", cfg(not(target_feature = "crt-static")))]
         unsafe extern "C" {}
     } else if #[cfg(target_os = "freebsd")] {
         #[link(name = "execinfo")]
         #[link(name = "pthread")]
         unsafe extern "C" {}
     } else if #[cfg(target_os = "netbsd")] {
         #[link(name = "pthread")]
         #[link(name = "rt")]
         unsafe extern "C" {}
     } else if #[cfg(any(target_os = "dragonfly", target_os = "openbsd", target_os = "cygwin"))] {
         #[link(name = "pthread")]
         unsafe extern "C" {}
     } else if #[cfg(target_os = "solaris")] {
         #[link(name = "socket")]
         #[link(name = "posix4")]
         #[link(name = "pthread")]
         #[link(name = "resolv")]
         unsafe extern "C" {}
     } else if #[cfg(target_os = "illumos")] {
         #[link(name = "socket")]
         #[link(name = "posix4")]
         #[link(name = "pthread")]
         #[link(name = "resolv")]
         #[link(name = "nsl")]
         // Use libumem for the (malloc-compatible) allocator
         #[link(name = "umem")]
         unsafe extern "C" {}
     } else if #[cfg(target_vendor = "apple")] {
         // Link to `libSystem.dylib`.
         //
         // Don't get confused by the presence of `System.framework`,
         // it is a deprecated wrapper over the dynamic library.
         #[link(name = "System")]
         unsafe extern "C" {}
     } else if #[cfg(target_os = "fuchsia")] {
         #[link(name = "zircon")]
         #[link(name = "fdio")]
         unsafe extern "C" {}
     } else if #[cfg(all(target_os = "linux", target_env = "uclibc"))] {
         #[link(name = "dl")]
         unsafe extern "C" {}
     } else if #[cfg(target_os = "vita")] {
         #[link(name = "pthread", kind = "static", modifiers = "-bundle")]
         unsafe extern "C" {}
     }
 }

 #[cfg(any(target_os = "espidf", target_os = "horizon", target_os = "vita", target_os = "nuttx"))]
 pub mod unsupported {
     use crate::io;

     pub fn unsupported<T>() -> io::Result<T> {
         Err(unsupported_err())
     }

     pub fn unsupported_err() -> io::Error {
         io::Error::UNSUPPORTED_PLATFORM
     }
 }
	#![allow(missing_docs, nonstandard_style)]

	use crate::io::ErrorKind;

	#[cfg(not(target_os = "espidf"))]
	#[macro_use]
	pub mod weak;

	#[cfg(target_os = "fuchsia")]
	pub mod fuchsia;
	pub mod futex;
	#[cfg(any(target_os = "linux", target_os = "android"))]
	pub mod kernel_copy;
	#[cfg(target_os = "linux")]
	pub mod linux;
	pub mod os;
	pub mod pipe;
	pub mod stack_overflow;
	pub mod sync;
	pub mod thread;
	pub mod thread_parking;
	pub mod time;

	#[cfg(target_os = "espidf")]
	pub fn init(_argc: isize, _argv: const const u8, _sigpipe: u8) {}

	#[cfg(not(target_os = "espidf"))]
	#[cfg_attr(target_os = "vita", allow(unused_variables))]
	// SAFETY: must be called only once during runtime initialization.
	// NOTE: this is not guaranteed to run, for example when Rust code is called externally.
	// See `fn init()` in `library/std/src/rt.rs` for docs on `sigpipe`.
	pub unsafe fn init(argc: isize, argv: const const u8, sigpipe: u8) {
	// The standard streams might be closed on application startup. To prevent
	// std::io::{stdin, stdout,stderr} objects from using other unrelated file
	// resources opened later, we reopen standards streams when they are closed.
	sanitize_standard_fds();

	// By default, some platforms will send a signal when an EPIPE error
	// would otherwise be delivered. This runtime doesn't install a SIGPIPE
	// handler, causing it to kill the program, which isn't exactly what we
	// want!
	//
	// Hence, we set SIGPIPE to ignore when the program starts up in order
	// to prevent this problem. Use `-Zon-broken-pipe=...` to alter this
	// behavior.
	reset_sigpipe(sigpipe);

	stack_overflow::init();
	#[cfg(not(target_os = "vita"))]
	crate::sys::args::init(argc, argv);

	// Normally, `thread::spawn` will call `Thread::set_name` but since this thread
	// already exists, we have to call it ourselves. We only do this on Apple targets
	// because some unix-like operating systems such as Linux share process-id and
	// thread-id for the main thread and so renaming the main thread will rename the
	// process and we only want to enable this on platforms we've tested.
	if cfg!(target_vendor = "apple") {
	thread::Thread::set_name(&c"main");
	}

	unsafe fn sanitize_standard_fds() {
	// fast path with a single syscall for systems with poll()
	#[cfg(not(any(
	miri,
	target_os = "emscripten",
	target_os = "fuchsia",
	target_os = "vxworks",
	target_os = "redox",
	target_os = "l4re",
	target_os = "horizon",
	target_os = "vita",
	target_os = "rtems",
	// The poll on Darwin doesn't set POLLNVAL for closed fds.
	target_vendor = "apple",
	)))]
	'poll: {
	#[cfg(not(all(target_os = "linux", target_env = "gnu")))]
	use libc::open as open64;
	#[cfg(all(target_os = "linux", target_env = "gnu"))]
	use libc::open64;

	use crate::sys::os::errno;
	let pfds: &mut [_] = &mut [
	libc::pollfd { fd: 0, events: 0, revents: 0 },
	libc::pollfd { fd: 1, events: 0, revents: 0 },
	libc::pollfd { fd: 2, events: 0, revents: 0 },
	];

	while libc::poll(pfds.as_mut_ptr(), 3, 0) == -1 {
	match errno() {
	libc::EINTR => continue,
	#[cfg(target_vendor = "unikraft")]
	libc::ENOSYS => {
	// Not all configurations of Unikraft enable `LIBPOSIX_EVENT`.
	break 'poll;
	}
	libc::EINVAL \| libc::EAGAIN \| libc::ENOMEM => {
	// RLIMIT_NOFILE or temporary allocation failures
	// may be preventing use of poll(), fall back to fcntl
	break 'poll;
	}
	_ => libc::abort(),
	}
	}
	for pfd in pfds {
	if pfd.revents & libc::POLLNVAL == 0 {
	continue;
	}
	if open64(c"/dev/null".as_ptr(), libc::O_RDWR, 0) == -1 {
	// If the stream is closed but we failed to reopen it, abort the
	// process. Otherwise we wouldn't preserve the safety of
	// operations on the corresponding Rust object Stdin, Stdout, or
	// Stderr.
	libc::abort();
	}
	}
	return;
	}

	// fallback in case poll isn't available or limited by RLIMIT_NOFILE
	#[cfg(not(any(
	// The standard fds are always available in Miri.
	miri,
	target_os = "emscripten",
	target_os = "fuchsia",
	target_os = "vxworks",
	target_os = "l4re",
	target_os = "horizon",
	target_os = "vita",
	)))]
	{
	#[cfg(not(all(target_os = "linux", target_env = "gnu")))]
	use libc::open as open64;
	#[cfg(all(target_os = "linux", target_env = "gnu"))]
	use libc::open64;

	use crate::sys::os::errno;
	for fd in 0..3 {
	if libc::fcntl(fd, libc::F_GETFD) == -1 && errno() == libc::EBADF {
	if open64(c"/dev/null".as_ptr(), libc::O_RDWR, 0) == -1 {
	// If the stream is closed but we failed to reopen it, abort the
	// process. Otherwise we wouldn't preserve the safety of
	// operations on the corresponding Rust object Stdin, Stdout, or
	// Stderr.
	libc::abort();
	}
	}
	}
	}
	}

	unsafe fn reset_sigpipe(#[allow(unused_variables)] sigpipe: u8) {
	#[cfg(not(any(
	target_os = "emscripten",
	target_os = "fuchsia",
	target_os = "horizon",
	target_os = "vxworks",
	target_os = "vita",
	// Unikraft's `signal` implementation is currently broken:
	// https://github.com/unikraft/lib-musl/issues/57
	target_vendor = "unikraft",
	)))]
	{
	// We don't want to add this as a public type to std, nor do we
	// want to `include!` a file from the compiler (which would break
	// Miri and xargo for example), so we choose to duplicate these
	// constants from `compiler/rustc_session/src/config/sigpipe.rs`.
	// See the other file for docs. NOTE: Make sure to keep them in
	// sync!
	mod sigpipe {
	pub const DEFAULT: u8 = 0;
	pub const INHERIT: u8 = 1;
	pub const SIG_IGN: u8 = 2;
	pub const SIG_DFL: u8 = 3;
	}

	let (sigpipe_attr_specified, handler) = match sigpipe {
	sigpipe::DEFAULT => (false, Some(libc::SIG_IGN)),
	sigpipe::INHERIT => (true, None),
	sigpipe::SIG_IGN => (true, Some(libc::SIG_IGN)),
	sigpipe::SIG_DFL => (true, Some(libc::SIG_DFL)),
	_ => unreachable!(),
	};
	if sigpipe_attr_specified {
	ON_BROKEN_PIPE_FLAG_USED.store(true, crate::sync::atomic::Ordering::Relaxed);
	}
	if let Some(handler) = handler {
	rtassert!(signal(libc::SIGPIPE, handler) != libc::SIG_ERR);
	#[cfg(target_os = "hurd")]
	{
	rtassert!(signal(libc::SIGLOST, handler) != libc::SIG_ERR);
	}
	}
	}
	}
	}

	// This is set (up to once) in reset_sigpipe.
	#[cfg(not(any(
	target_os = "espidf",
	target_os = "emscripten",
	target_os = "fuchsia",
	target_os = "horizon",
	target_os = "vxworks",
	target_os = "vita",
	)))]
	static ON_BROKEN_PIPE_FLAG_USED: crate::sync::atomic::AtomicBool =
	crate::sync::atomic::AtomicBool::new(false);

	#[cfg(not(any(
	target_os = "espidf",
	target_os = "emscripten",
	target_os = "fuchsia",
	target_os = "horizon",
	target_os = "vxworks",
	target_os = "vita",
	target_os = "nuttx",
	)))]
	pub(crate) fn on_broken_pipe_flag_used() -> bool {
	ON_BROKEN_PIPE_FLAG_USED.load(crate::sync::atomic::Ordering::Relaxed)
	}

	// SAFETY: must be called only once during runtime cleanup.
	// NOTE: this is not guaranteed to run, for example when the program aborts.
	pub unsafe fn cleanup() {
	stack_overflow::cleanup();
	}

	#[allow(unused_imports)]
	pub use libc::signal;

	#[inline]
	pub(crate) fn is_interrupted(errno: i32) -> bool {
	errno == libc::EINTR
	}

	pub fn decode_error_kind(errno: i32) -> ErrorKind {
	use ErrorKind::*;
	match errno as libc::c_int {
	libc::E2BIG => ArgumentListTooLong,
	libc::EADDRINUSE => AddrInUse,
	libc::EADDRNOTAVAIL => AddrNotAvailable,
	libc::EBUSY => ResourceBusy,
	libc::ECONNABORTED => ConnectionAborted,
	libc::ECONNREFUSED => ConnectionRefused,
	libc::ECONNRESET => ConnectionReset,
	libc::EDEADLK => Deadlock,
	libc::EDQUOT => QuotaExceeded,
	libc::EEXIST => AlreadyExists,
	libc::EFBIG => FileTooLarge,
	libc::EHOSTUNREACH => HostUnreachable,
	libc::EINTR => Interrupted,
	libc::EINVAL => InvalidInput,
	libc::EISDIR => IsADirectory,
	libc::ELOOP => FilesystemLoop,
	libc::ENOENT => NotFound,
	libc::ENOMEM => OutOfMemory,
	libc::ENOSPC => StorageFull,
	libc::ENOSYS => Unsupported,
	libc::EMLINK => TooManyLinks,
	libc::ENAMETOOLONG => InvalidFilename,
	libc::ENETDOWN => NetworkDown,
	libc::ENETUNREACH => NetworkUnreachable,
	libc::ENOTCONN => NotConnected,
	libc::ENOTDIR => NotADirectory,
	#[cfg(not(target_os = "aix"))]
	libc::ENOTEMPTY => DirectoryNotEmpty,
	libc::EPIPE => BrokenPipe,
	libc::EROFS => ReadOnlyFilesystem,
	libc::ESPIPE => NotSeekable,
	libc::ESTALE => StaleNetworkFileHandle,
	libc::ETIMEDOUT => TimedOut,
	libc::ETXTBSY => ExecutableFileBusy,
	libc::EXDEV => CrossesDevices,
	libc::EINPROGRESS => InProgress,
	libc::EOPNOTSUPP => Unsupported,

	libc::EACCES \| libc::EPERM => PermissionDenied,

	// These two constants can have the same value on some systems,
	// but different values on others, so we can't use a match
	// clause
	x if x == libc::EAGAIN \|\| x == libc::EWOULDBLOCK => WouldBlock,

	_ => Uncategorized,
	}
	}

	#[doc(hidden)]
	pub trait IsMinusOne {
	fn is_minus_one(&self) -> bool;
	}

	macro_rules! impl_is_minus_one {
	($($t:ident)*) => ($(impl IsMinusOne for $t {
	fn is_minus_one(&self) -> bool {
	*self == -1
	}
	})*)
	}

	impl_is_minus_one! { i8 i16 i32 i64 isize }

	/// Converts native return values to Result using the -1 means error is in `errno` convention.
	/// Non-error values are `Ok`-wrapped.
	pub fn cvt<T: IsMinusOne>(t: T) -> crate::io::Result<T> {
	if t.is_minus_one() { Err(crate::io::Error::last_os_error()) } else { Ok(t) }
	}

	/// `-1` → look at `errno` → retry on `EINTR`. Otherwise `Ok()`-wrap the closure return value.
	pub fn cvt_r<T, F>(mut f: F) -> crate::io::Result<T>
	where
	T: IsMinusOne,
	F: FnMut() -> T,
	{
	loop {
	match cvt(f()) {
	Err(ref e) if e.is_interrupted() => {}
	other => return other,
	}
	}
	}

	#[allow(dead_code)] // Not used on all platforms.
	/// Zero means `Ok()`, all other values are treated as raw OS errors. Does not look at `errno`.
	pub fn cvt_nz(error: libc::c_int) -> crate::io::Result<()> {
	if error == 0 { Ok(()) } else { Err(crate::io::Error::from_raw_os_error(error)) }
	}

	// libc::abort() will run the SIGABRT handler. That's fine because anyone who
	// installs a SIGABRT handler already has to expect it to run in Very Bad
	// situations (eg, malloc crashing).
	//
	// Current glibc's abort() function unblocks SIGABRT, raises SIGABRT, clears the
	// SIGABRT handler and raises it again, and then starts to get creative.
	//
	// See the public documentation for `intrinsics::abort()` and `process::abort()`
	// for further discussion.
	//
	// There is confusion about whether libc::abort() flushes stdio streams.
	// libc::abort() is required by ISO C 99 (7.14.1.1p5) to be async-signal-safe,
	// so flushing streams is at least extremely hard, if not entirely impossible.
	//
	// However, some versions of POSIX (eg IEEE Std 1003.1-2001) required abort to
	// do so. In 1003.1-2004 this was fixed.
	//
	// glibc's implementation did the flush, unsafely, before glibc commit
	// 91e7cf982d01 `abort: Do not flush stdio streams [BZ #15436]` by Florian
	// Weimer. According to glibc's NEWS:
	//
	// The abort function terminates the process immediately, without flushing
	// stdio streams. Previous glibc versions used to flush streams, resulting
	// in deadlocks and further data corruption. This change also affects
	// process aborts as the result of assertion failures.
	//
	// This is an accurate description of the problem. The only solution for
	// program with nontrivial use of C stdio is a fixed libc - one which does not
	// try to flush in abort - since even libc-internal errors, and assertion
	// failures generated from C, will go via abort().
	//
	// On systems with old, buggy, libcs, the impact can be severe for a
	// multithreaded C program. It is much less severe for Rust, because Rust
	// stdlib doesn't use libc stdio buffering. In a typical Rust program, which
	// does not use C stdio, even a buggy libc::abort() is, in fact, safe.
	pub fn abort_internal() -> ! {
	unsafe { libc::abort() }
	}

	cfg_if::cfg_if! {
	if #[cfg(target_os = "android")] {
	#[link(name = "dl", kind = "static", modifiers = "-bundle",
	cfg(target_feature = "crt-static"))]
	#[link(name = "dl", cfg(not(target_feature = "crt-static")))]
	#[link(name = "log", cfg(not(target_feature = "crt-static")))]
	unsafe extern "C" {}
	} else if #[cfg(target_os = "freebsd")] {
	#[link(name = "execinfo")]
	#[link(name = "pthread")]
	unsafe extern "C" {}
	} else if #[cfg(target_os = "netbsd")] {
	#[link(name = "pthread")]
	#[link(name = "rt")]
	unsafe extern "C" {}
	} else if #[cfg(any(target_os = "dragonfly", target_os = "openbsd", target_os = "cygwin"))] {
	#[link(name = "pthread")]
	unsafe extern "C" {}
	} else if #[cfg(target_os = "solaris")] {
	#[link(name = "socket")]
	#[link(name = "posix4")]
	#[link(name = "pthread")]
	#[link(name = "resolv")]
	unsafe extern "C" {}
	} else if #[cfg(target_os = "illumos")] {
	#[link(name = "socket")]
	#[link(name = "posix4")]
	#[link(name = "pthread")]
	#[link(name = "resolv")]
	#[link(name = "nsl")]
	// Use libumem for the (malloc-compatible) allocator
	#[link(name = "umem")]
	unsafe extern "C" {}
	} else if #[cfg(target_vendor = "apple")] {
	// Link to `libSystem.dylib`.
	//
	// Don't get confused by the presence of `System.framework`,
	// it is a deprecated wrapper over the dynamic library.
	#[link(name = "System")]
	unsafe extern "C" {}
	} else if #[cfg(target_os = "fuchsia")] {
	#[link(name = "zircon")]
	#[link(name = "fdio")]
	unsafe extern "C" {}
	} else if #[cfg(all(target_os = "linux", target_env = "uclibc"))] {
	#[link(name = "dl")]
	unsafe extern "C" {}
	} else if #[cfg(target_os = "vita")] {
	#[link(name = "pthread", kind = "static", modifiers = "-bundle")]
	unsafe extern "C" {}
	}
	}

	#[cfg(any(target_os = "espidf", target_os = "horizon", target_os = "vita", target_os = "nuttx"))]
	pub mod unsupported {
	use crate::io;

	pub fn unsupported<T>() -> io::Result<T> {
	Err(unsupported_err())
	}

	pub fn unsupported_err() -> io::Error {
	io::Error::UNSUPPORTED_PLATFORM
	}
	}