Alex Crichton 6968ccfd7a rollup merge of #23651: alexcrichton/unwind-try
This commit provides a safe, but unstable interface for the `try` functionality
of running a closure and determining whether it panicked or not.

There are two primary reasons that this function was previously marked `unsafe`:

1. A vanilla version of this function exposes the problem of exception safety by
   allowing a bare try/catch in the language. It is not clear whether this
   concern should be directly tied to `unsafe` in Rust at the API level. At this
   time, however, the bounds on `ffi::try` require the closure to be both
   `'static` and `Send` (mirroring those of `thread::spawn`). It may be possible
   to relax the bounds in the future, but for now it's the level of safety that
   we're willing to commit to.

2. Panicking while panicking will leak resources by not running destructors.
   Because panicking is still controlled by the standard library, safeguards
   remain in place to prevent this from happening.

The new API is now called `catch_panic` and is marked as `#[unstable]` for now.
2015-03-27 10:07:42 -07:00

1076 lines
36 KiB
Rust

// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Native threads
//!
//! ## The threading model
//!
//! An executing Rust program consists of a collection of native OS threads,
//! each with their own stack and local state.
//!
//! Communication between threads can be done through
//! [channels](../../std/sync/mpsc/index.html), Rust's message-passing
//! types, along with [other forms of thread
//! synchronization](../../std/sync/index.html) and shared-memory data
//! structures. In particular, types that are guaranteed to be
//! threadsafe are easily shared between threads using the
//! atomically-reference-counted container,
//! [`Arc`](../../std/sync/struct.Arc.html).
//!
//! Fatal logic errors in Rust cause *thread panic*, during which
//! a thread will unwind the stack, running destructors and freeing
//! owned resources. Thread panic is unrecoverable from within
//! the panicking thread (i.e. there is no 'try/catch' in Rust), but
//! the panic may optionally be detected from a different thread. If
//! the main thread panics, the application will exit with a non-zero
//! exit code.
//!
//! When the main thread of a Rust program terminates, the entire program shuts
//! down, even if other threads are still running. However, this module provides
//! convenient facilities for automatically waiting for the termination of a
//! child thread (i.e., join).
//!
//! ## The `Thread` type
//!
//! Threads are represented via the `Thread` type, which you can
//! get in one of two ways:
//!
//! * By spawning a new thread, e.g. using the `thread::spawn` function.
//! * By requesting the current thread, using the `thread::current` function.
//!
//! Threads can be named, and provide some built-in support for low-level
//! synchronization (described below).
//!
//! The `thread::current()` function is available even for threads not spawned
//! by the APIs of this module.
//!
//! ## Spawning a thread
//!
//! A new thread can be spawned using the `thread::spawn` function:
//!
//! ```rust
//! use std::thread;
//!
//! thread::spawn(move || {
//! // some work here
//! });
//! ```
//!
//! In this example, the spawned thread is "detached" from the current
//! thread. This means that it can outlive its parent (the thread that spawned
//! it), unless this parent is the main thread.
//!
//! ## Scoped threads
//!
//! Often a parent thread uses a child thread to perform some particular task,
//! and at some point must wait for the child to complete before continuing.
//! For this scenario, use the `thread::scoped` function:
//!
//! ```rust
//! use std::thread;
//!
//! let guard = thread::scoped(move || {
//! // some work here
//! });
//!
//! // do some other work in the meantime
//! let output = guard.join();
//! ```
//!
//! The `scoped` function doesn't return a `Thread` directly; instead,
//! it returns a *join guard*. The join guard is an RAII-style guard
//! that will automatically join the child thread (block until it
//! terminates) when it is dropped. You can join the child thread in
//! advance by calling the `join` method on the guard, which will also
//! return the result produced by the thread. A handle to the thread
//! itself is available via the `thread` method of the join guard.
//!
//! ## Configuring threads
//!
//! A new thread can be configured before it is spawned via the `Builder` type,
//! which currently allows you to set the name, stack size, and writers for
//! `println!` and `panic!` for the child thread:
//!
//! ```rust
//! use std::thread;
//!
//! thread::Builder::new().name("child1".to_string()).spawn(move || {
//! println!("Hello, world!");
//! });
//! ```
//!
//! ## Blocking support: park and unpark
//!
//! Every thread is equipped with some basic low-level blocking support, via the
//! `park` and `unpark` functions.
//!
//! Conceptually, each `Thread` handle has an associated token, which is
//! initially not present:
//!
//! * The `thread::park()` function blocks the current thread unless or until
//! the token is available for its thread handle, at which point it atomically
//! consumes the token. It may also return *spuriously*, without consuming the
//! token. `thread::park_timeout()` does the same, but allows specifying a
//! maximum time to block the thread for.
//!
//! * The `unpark()` method on a `Thread` atomically makes the token available
//! if it wasn't already.
//!
//! In other words, each `Thread` acts a bit like a semaphore with initial count
//! 0, except that the semaphore is *saturating* (the count cannot go above 1),
//! and can return spuriously.
//!
//! The API is typically used by acquiring a handle to the current thread,
//! placing that handle in a shared data structure so that other threads can
//! find it, and then `park`ing. When some desired condition is met, another
//! thread calls `unpark` on the handle.
//!
//! The motivation for this design is twofold:
//!
//! * It avoids the need to allocate mutexes and condvars when building new
//! synchronization primitives; the threads already provide basic blocking/signaling.
//!
//! * It can be implemented very efficiently on many platforms.
//!
//! ## Thread-local storage
//!
//! This module also provides an implementation of thread local storage for Rust
//! programs. Thread local storage is a method of storing data into a global
//! variable which each thread in the program will have its own copy of.
//! Threads do not share this data, so accesses do not need to be synchronized.
//!
//! At a high level, this module provides two variants of storage:
//!
//! * Owned thread-local storage. This is a type of thread local key which
//! owns the value that it contains, and will destroy the value when the
//! thread exits. This variant is created with the `thread_local!` macro and
//! can contain any value which is `'static` (no borrowed pointers).
//!
//! * Scoped thread-local storage. This type of key is used to store a reference
//! to a value into local storage temporarily for the scope of a function
//! call. There are no restrictions on what types of values can be placed
//! into this key.
//!
//! Both forms of thread local storage provide an accessor function, `with`,
//! which will yield a shared reference to the value to the specified
//! closure. Thread-local keys only allow shared access to values as there is no
//! way to guarantee uniqueness if a mutable borrow was allowed. Most values
//! will want to make use of some form of **interior mutability** through the
//! `Cell` or `RefCell` types.
#![stable(feature = "rust1", since = "1.0.0")]
#[stable(feature = "rust1", since = "1.0.0")]
pub use self::__local::{LocalKey, LocalKeyState};
#[unstable(feature = "scoped_tls",
reason = "scoped TLS has yet to have wide enough use to fully consider \
stabilizing its interface")]
pub use self::__scoped::ScopedKey;
use prelude::v1::*;
use any::Any;
use cell::UnsafeCell;
use fmt;
use io;
use marker::PhantomData;
use rt::{self, unwind};
use sync::{Mutex, Condvar, Arc};
use sys::thread as imp;
use sys_common::{stack, thread_info};
use thunk::Thunk;
use time::Duration;
#[allow(deprecated)] use old_io::Writer;
////////////////////////////////////////////////////////////////////////////////
// Thread-local storage
////////////////////////////////////////////////////////////////////////////////
#[macro_use]
#[doc(hidden)]
#[path = "local.rs"] pub mod __local;
#[macro_use]
#[doc(hidden)]
#[path = "scoped.rs"] pub mod __scoped;
////////////////////////////////////////////////////////////////////////////////
// Builder
////////////////////////////////////////////////////////////////////////////////
/// Thread configuration. Provides detailed control over the properties
/// and behavior of new threads.
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Builder {
// A name for the thread-to-be, for identification in panic messages
name: Option<String>,
// The size of the stack for the spawned thread
stack_size: Option<usize>,
}
impl Builder {
/// Generate the base configuration for spawning a thread, from which
/// configuration methods can be chained.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn new() -> Builder {
Builder {
name: None,
stack_size: None,
}
}
/// Name the thread-to-be. Currently the name is used for identification
/// only in panic messages.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn name(mut self, name: String) -> Builder {
self.name = Some(name);
self
}
/// Set the size of the stack for the new thread.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn stack_size(mut self, size: usize) -> Builder {
self.stack_size = Some(size);
self
}
/// Redirect thread-local stdout.
#[unstable(feature = "std_misc",
reason = "Will likely go away after proc removal")]
#[deprecated(since = "1.0.0",
reason = "the old I/O module is deprecated and this function \
will be removed with no replacement")]
#[allow(deprecated)]
pub fn stdout(self, _stdout: Box<Writer + Send + 'static>) -> Builder {
self
}
/// Redirect thread-local stderr.
#[unstable(feature = "std_misc",
reason = "Will likely go away after proc removal")]
#[deprecated(since = "1.0.0",
reason = "the old I/O module is deprecated and this function \
will be removed with no replacement")]
#[allow(deprecated)]
pub fn stderr(self, _stderr: Box<Writer + Send + 'static>) -> Builder {
self
}
/// Spawn a new thread, and return a join handle for it.
///
/// The child thread may outlive the parent (unless the parent thread
/// is the main thread; the whole process is terminated when the main
/// thread finishes.) The join handle can be used to block on
/// termination of the child thread, including recovering its panics.
///
/// # Errors
///
/// Unlike the `spawn` free function, this method yields an
/// `io::Result` to capture any failure to create the thread at
/// the OS level.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn spawn<F>(self, f: F) -> io::Result<JoinHandle> where
F: FnOnce(), F: Send + 'static
{
self.spawn_inner(Thunk::new(f)).map(|i| JoinHandle(i))
}
/// Spawn a new child thread that must be joined within a given
/// scope, and return a `JoinGuard`.
///
/// The join guard can be used to explicitly join the child thread (via
/// `join`), returning `Result<T>`, or it will implicitly join the child
/// upon being dropped. Because the child thread may refer to data on the
/// current thread's stack (hence the "scoped" name), it cannot be detached;
/// it *must* be joined before the relevant stack frame is popped. See the
/// module documentation for additional details.
///
/// # Errors
///
/// Unlike the `scoped` free function, this method yields an
/// `io::Result` to capture any failure to create the thread at
/// the OS level.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn scoped<'a, T, F>(self, f: F) -> io::Result<JoinGuard<'a, T>> where
T: Send + 'a, F: FnOnce() -> T, F: Send + 'a
{
self.spawn_inner(Thunk::new(f)).map(|inner| {
JoinGuard { inner: inner, _marker: PhantomData }
})
}
fn spawn_inner<T: Send>(self, f: Thunk<(), T>) -> io::Result<JoinInner<T>> {
let Builder { name, stack_size } = self;
let stack_size = stack_size.unwrap_or(rt::min_stack());
let my_thread = Thread::new(name);
let their_thread = my_thread.clone();
let my_packet = Packet(Arc::new(UnsafeCell::new(None)));
let their_packet = Packet(my_packet.0.clone());
// Spawning a new OS thread guarantees that __morestack will never get
// triggered, but we must manually set up the actual stack bounds once
// this function starts executing. This raises the lower limit by a bit
// because by the time that this function is executing we've already
// consumed at least a little bit of stack (we don't know the exact byte
// address at which our stack started).
let main = move || {
let something_around_the_top_of_the_stack = 1;
let addr = &something_around_the_top_of_the_stack as *const i32;
let my_stack_top = addr as usize;
let my_stack_bottom = my_stack_top - stack_size + 1024;
unsafe {
if let Some(name) = their_thread.name() {
imp::set_name(name);
}
stack::record_os_managed_stack_bounds(my_stack_bottom,
my_stack_top);
thread_info::set(imp::guard::current(), their_thread);
}
let mut output = None;
let try_result = {
let ptr = &mut output;
// There are two primary reasons that general try/catch is
// unsafe. The first is that we do not support nested
// try/catch. The fact that this is happening in a newly-spawned
// thread suffices. The second is that unwinding while unwinding
// is not defined. We take care of that by having an
// 'unwinding' flag in the thread itself. For these reasons,
// this unsafety should be ok.
unsafe {
unwind::try(move || *ptr = Some(f.invoke(())))
}
};
unsafe {
*their_packet.0.get() = Some(match (output, try_result) {
(Some(data), Ok(_)) => Ok(data),
(None, Err(cause)) => Err(cause),
_ => unreachable!()
});
}
};
Ok(JoinInner {
native: try!(unsafe { imp::create(stack_size, Thunk::new(main)) }),
thread: my_thread,
packet: my_packet,
joined: false,
})
}
}
////////////////////////////////////////////////////////////////////////////////
// Free functions
////////////////////////////////////////////////////////////////////////////////
/// Spawn a new thread, returning a `JoinHandle` for it.
///
/// The join handle will implicitly *detach* the child thread upon being
/// dropped. In this case, the child thread may outlive the parent (unless
/// the parent thread is the main thread; the whole process is terminated when
/// the main thread finishes.) Additionally, the join handle provides a `join`
/// method that can be used to join the child thread. If the child thread
/// panics, `join` will return an `Err` containing the argument given to
/// `panic`.
///
/// # Panics
///
/// Panicks if the OS fails to create a thread; use `Builder::spawn`
/// to recover from such errors.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn spawn<F>(f: F) -> JoinHandle where F: FnOnce(), F: Send + 'static {
Builder::new().spawn(f).unwrap()
}
/// Spawn a new *scoped* thread, returning a `JoinGuard` for it.
///
/// The join guard can be used to explicitly join the child thread (via
/// `join`), returning `Result<T>`, or it will implicitly join the child
/// upon being dropped. Because the child thread may refer to data on the
/// current thread's stack (hence the "scoped" name), it cannot be detached;
/// it *must* be joined before the relevant stack frame is popped. See the
/// module documentation for additional details.
///
/// # Panics
///
/// Panicks if the OS fails to create a thread; use `Builder::scoped`
/// to recover from such errors.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn scoped<'a, T, F>(f: F) -> JoinGuard<'a, T> where
T: Send + 'a, F: FnOnce() -> T, F: Send + 'a
{
Builder::new().scoped(f).unwrap()
}
/// Gets a handle to the thread that invokes it.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn current() -> Thread {
thread_info::current_thread()
}
/// Cooperatively give up a timeslice to the OS scheduler.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn yield_now() {
unsafe { imp::yield_now() }
}
/// Determines whether the current thread is unwinding because of panic.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn panicking() -> bool {
unwind::panicking()
}
/// Invoke a closure, capturing the cause of panic if one occurs.
///
/// This function will return `Ok(())` if the closure does not panic, and will
/// return `Err(cause)` if the closure panics. The `cause` returned is the
/// object with which panic was originally invoked.
///
/// It is currently undefined behavior to unwind from Rust code into foreign
/// code, so this function is particularly useful when Rust is called from
/// another language (normally C). This can run arbitrary Rust code, capturing a
/// panic and allowing a graceful handling of the error.
///
/// It is **not** recommended to use this function for a general try/catch
/// mechanism. The `Result` type is more appropriate to use for functions that
/// can fail on a regular basis.
///
/// The closure provided is required to adhere to the `'static` bound to ensure
/// that it cannot reference data in the parent stack frame, mitigating problems
/// with exception safety. Furthermore, a `Send` bound is also required,
/// providing the same safety guarantees as `thread::spawn` (ensuring the
/// closure is properly isolated from the parent).
///
/// # Examples
///
/// ```
/// # #![feature(catch_panic)]
/// use std::thread;
///
/// let result = thread::catch_panic(|| {
/// println!("hello!");
/// });
/// assert!(result.is_ok());
///
/// let result = thread::catch_panic(|| {
/// panic!("oh no!");
/// });
/// assert!(result.is_err());
/// ```
#[unstable(feature = "catch_panic", reason = "recent API addition")]
pub fn catch_panic<F, R>(f: F) -> Result<R>
where F: FnOnce() -> R + Send + 'static
{
let mut result = None;
unsafe {
let result = &mut result;
try!(::rt::unwind::try(move || *result = Some(f())))
}
Ok(result.unwrap())
}
/// Put the current thread to sleep for the specified amount of time.
///
/// The thread may sleep longer than the duration specified due to scheduling
/// specifics or platform-dependent functionality. Note that on unix platforms
/// this function will not return early due to a signal being received or a
/// spurious wakeup.
#[unstable(feature = "thread_sleep",
reason = "recently added, needs an RFC, and `Duration` itself is \
unstable")]
pub fn sleep(dur: Duration) {
imp::sleep(dur)
}
/// Block unless or until the current thread's token is made available (may wake spuriously).
///
/// See the module doc for more detail.
//
// The implementation currently uses the trivial strategy of a Mutex+Condvar
// with wakeup flag, which does not actually allow spurious wakeups. In the
// future, this will be implemented in a more efficient way, perhaps along the lines of
// http://cr.openjdk.java.net/~stefank/6989984.1/raw_files/new/src/os/linux/vm/os_linux.cpp
// or futuxes, and in either case may allow spurious wakeups.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn park() {
let thread = current();
let mut guard = thread.inner.lock.lock().unwrap();
while !*guard {
guard = thread.inner.cvar.wait(guard).unwrap();
}
*guard = false;
}
/// Block unless or until the current thread's token is made available or
/// the specified duration has been reached (may wake spuriously).
///
/// The semantics of this function are equivalent to `park()` except that the
/// thread will be blocked for roughly no longer than *duration*. This method
/// should not be used for precise timing due to anomalies such as
/// preemption or platform differences that may not cause the maximum
/// amount of time waited to be precisely *duration* long.
///
/// See the module doc for more detail.
#[unstable(feature = "std_misc", reason = "recently introduced, depends on Duration")]
pub fn park_timeout(duration: Duration) {
let thread = current();
let mut guard = thread.inner.lock.lock().unwrap();
if !*guard {
let (g, _) = thread.inner.cvar.wait_timeout(guard, duration).unwrap();
guard = g;
}
*guard = false;
}
////////////////////////////////////////////////////////////////////////////////
// Thread
////////////////////////////////////////////////////////////////////////////////
/// The internal representation of a `Thread` handle
struct Inner {
name: Option<String>,
lock: Mutex<bool>, // true when there is a buffered unpark
cvar: Condvar,
}
unsafe impl Sync for Inner {}
#[derive(Clone)]
#[stable(feature = "rust1", since = "1.0.0")]
/// A handle to a thread.
pub struct Thread {
inner: Arc<Inner>,
}
impl Thread {
// Used only internally to construct a thread object without spawning
fn new(name: Option<String>) -> Thread {
Thread {
inner: Arc::new(Inner {
name: name,
lock: Mutex::new(false),
cvar: Condvar::new(),
})
}
}
/// Deprecated: use module-level free function.
#[deprecated(since = "1.0.0", reason = "use module-level free function")]
#[unstable(feature = "std_misc",
reason = "may change with specifics of new Send semantics")]
pub fn spawn<F>(f: F) -> Thread where F: FnOnce(), F: Send + 'static {
Builder::new().spawn(f).unwrap().thread().clone()
}
/// Deprecated: use module-level free function.
#[deprecated(since = "1.0.0", reason = "use module-level free function")]
#[unstable(feature = "std_misc",
reason = "may change with specifics of new Send semantics")]
pub fn scoped<'a, T, F>(f: F) -> JoinGuard<'a, T> where
T: Send + 'a, F: FnOnce() -> T, F: Send + 'a
{
Builder::new().scoped(f).unwrap()
}
/// Deprecated: use module-level free function.
#[deprecated(since = "1.0.0", reason = "use module-level free function")]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn current() -> Thread {
thread_info::current_thread()
}
/// Deprecated: use module-level free function.
#[deprecated(since = "1.0.0", reason = "use module-level free function")]
#[unstable(feature = "std_misc", reason = "name may change")]
pub fn yield_now() {
unsafe { imp::yield_now() }
}
/// Deprecated: use module-level free function.
#[deprecated(since = "1.0.0", reason = "use module-level free function")]
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn panicking() -> bool {
unwind::panicking()
}
/// Deprecated: use module-level free function.
#[deprecated(since = "1.0.0", reason = "use module-level free function")]
#[unstable(feature = "std_misc", reason = "recently introduced")]
pub fn park() {
let thread = current();
let mut guard = thread.inner.lock.lock().unwrap();
while !*guard {
guard = thread.inner.cvar.wait(guard).unwrap();
}
*guard = false;
}
/// Deprecated: use module-level free function.
#[deprecated(since = "1.0.0", reason = "use module-level free function")]
#[unstable(feature = "std_misc", reason = "recently introduced")]
pub fn park_timeout(duration: Duration) {
let thread = current();
let mut guard = thread.inner.lock.lock().unwrap();
if !*guard {
let (g, _) = thread.inner.cvar.wait_timeout(guard, duration).unwrap();
guard = g;
}
*guard = false;
}
/// Atomically makes the handle's token available if it is not already.
///
/// See the module doc for more detail.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn unpark(&self) {
let mut guard = self.inner.lock.lock().unwrap();
if !*guard {
*guard = true;
self.inner.cvar.notify_one();
}
}
/// Get the thread's name.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn name(&self) -> Option<&str> {
self.inner.name.as_ref().map(|s| &**s)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Debug for Thread {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Debug::fmt(&self.name(), f)
}
}
// a hack to get around privacy restrictions
impl thread_info::NewThread for Thread {
fn new(name: Option<String>) -> Thread { Thread::new(name) }
}
////////////////////////////////////////////////////////////////////////////////
// JoinHandle and JoinGuard
////////////////////////////////////////////////////////////////////////////////
/// Indicates the manner in which a thread exited.
///
/// A thread that completes without panicking is considered to exit successfully.
#[stable(feature = "rust1", since = "1.0.0")]
pub type Result<T> = ::result::Result<T, Box<Any + Send + 'static>>;
struct Packet<T>(Arc<UnsafeCell<Option<Result<T>>>>);
unsafe impl<T:Send> Send for Packet<T> {}
unsafe impl<T> Sync for Packet<T> {}
/// Inner representation for JoinHandle and JoinGuard
struct JoinInner<T> {
native: imp::rust_thread,
thread: Thread,
packet: Packet<T>,
joined: bool,
}
impl<T> JoinInner<T> {
fn join(&mut self) -> Result<T> {
assert!(!self.joined);
unsafe { imp::join(self.native) };
self.joined = true;
unsafe {
(*self.packet.0.get()).take().unwrap()
}
}
}
/// An owned permission to join on a thread (block on its termination).
///
/// Unlike a `JoinGuard`, a `JoinHandle` *detaches* the child thread
/// when it is dropped, rather than automatically joining on drop.
///
/// Due to platform restrictions, it is not possible to `Clone` this
/// handle: the ability to join a child thread is a uniquely-owned
/// permission.
#[stable(feature = "rust1", since = "1.0.0")]
pub struct JoinHandle(JoinInner<()>);
impl JoinHandle {
/// Extract a handle to the underlying thread
#[stable(feature = "rust1", since = "1.0.0")]
pub fn thread(&self) -> &Thread {
&self.0.thread
}
/// Wait for the associated thread to finish.
///
/// If the child thread panics, `Err` is returned with the parameter given
/// to `panic`.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn join(mut self) -> Result<()> {
self.0.join()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl Drop for JoinHandle {
fn drop(&mut self) {
if !self.0.joined {
unsafe { imp::detach(self.0.native) }
}
}
}
/// An RAII-style guard that will block until thread termination when dropped.
///
/// The type `T` is the return type for the thread's main function.
///
/// Joining on drop is necessary to ensure memory safety when stack
/// data is shared between a parent and child thread.
///
/// Due to platform restrictions, it is not possible to `Clone` this
/// handle: the ability to join a child thread is a uniquely-owned
/// permission.
#[must_use = "thread will be immediately joined if `JoinGuard` is not used"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct JoinGuard<'a, T: Send + 'a> {
inner: JoinInner<T>,
_marker: PhantomData<&'a T>,
}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<'a, T: Send + 'a> Sync for JoinGuard<'a, T> {}
impl<'a, T: Send + 'a> JoinGuard<'a, T> {
/// Extract a handle to the thread this guard will join on.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn thread(&self) -> &Thread {
&self.inner.thread
}
/// Wait for the associated thread to finish, returning the result of the thread's
/// calculation.
///
/// # Panics
///
/// Panics on the child thread are propagated by panicking the parent.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn join(mut self) -> T {
match self.inner.join() {
Ok(res) => res,
Err(_) => panic!("child thread {:?} panicked", self.thread()),
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Send> JoinGuard<'static, T> {
/// Detaches the child thread, allowing it to outlive its parent.
#[deprecated(since = "1.0.0", reason = "use spawn instead")]
#[unstable(feature = "std_misc")]
pub fn detach(mut self) {
unsafe { imp::detach(self.inner.native) };
self.inner.joined = true; // avoid joining in the destructor
}
}
#[unsafe_destructor]
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T: Send + 'a> Drop for JoinGuard<'a, T> {
fn drop(&mut self) {
if !self.inner.joined {
if self.inner.join().is_err() {
panic!("child thread {:?} panicked", self.thread());
}
}
}
}
////////////////////////////////////////////////////////////////////////////////
// Tests
////////////////////////////////////////////////////////////////////////////////
#[cfg(test)]
mod test {
use prelude::v1::*;
use any::Any;
use sync::mpsc::{channel, Sender};
use boxed::BoxAny;
use result;
use std::old_io::{ChanReader, ChanWriter};
use super::{Builder};
use thread;
use thunk::Thunk;
use time::Duration;
// !!! These tests are dangerous. If something is buggy, they will hang, !!!
// !!! instead of exiting cleanly. This might wedge the buildbots. !!!
#[test]
fn test_unnamed_thread() {
thread::spawn(move|| {
assert!(thread::current().name().is_none());
}).join().ok().unwrap();
}
#[test]
fn test_named_thread() {
Builder::new().name("ada lovelace".to_string()).scoped(move|| {
assert!(thread::current().name().unwrap() == "ada lovelace".to_string());
}).unwrap().join();
}
#[test]
fn test_run_basic() {
let (tx, rx) = channel();
thread::spawn(move|| {
tx.send(()).unwrap();
});
rx.recv().unwrap();
}
#[test]
fn test_join_success() {
assert!(thread::scoped(move|| -> String {
"Success!".to_string()
}).join() == "Success!");
}
#[test]
fn test_join_panic() {
match thread::spawn(move|| {
panic!()
}).join() {
result::Result::Err(_) => (),
result::Result::Ok(()) => panic!()
}
}
#[test]
fn test_scoped_success() {
let res = thread::scoped(move|| -> String {
"Success!".to_string()
}).join();
assert!(res == "Success!");
}
#[test]
#[should_fail]
fn test_scoped_panic() {
thread::scoped(|| panic!()).join();
}
#[test]
#[should_fail]
fn test_scoped_implicit_panic() {
let _ = thread::scoped(|| panic!());
}
#[test]
fn test_spawn_sched() {
use clone::Clone;
let (tx, rx) = channel();
fn f(i: i32, tx: Sender<()>) {
let tx = tx.clone();
thread::spawn(move|| {
if i == 0 {
tx.send(()).unwrap();
} else {
f(i - 1, tx);
}
});
}
f(10, tx);
rx.recv().unwrap();
}
#[test]
fn test_spawn_sched_childs_on_default_sched() {
let (tx, rx) = channel();
thread::spawn(move|| {
thread::spawn(move|| {
tx.send(()).unwrap();
});
});
rx.recv().unwrap();
}
fn avoid_copying_the_body<F>(spawnfn: F) where F: FnOnce(Thunk<'static>) {
let (tx, rx) = channel();
let x: Box<_> = box 1;
let x_in_parent = (&*x) as *const i32 as usize;
spawnfn(Thunk::new(move|| {
let x_in_child = (&*x) as *const i32 as usize;
tx.send(x_in_child).unwrap();
}));
let x_in_child = rx.recv().unwrap();
assert_eq!(x_in_parent, x_in_child);
}
#[test]
fn test_avoid_copying_the_body_spawn() {
avoid_copying_the_body(|v| {
thread::spawn(move || v.invoke(()));
});
}
#[test]
fn test_avoid_copying_the_body_thread_spawn() {
avoid_copying_the_body(|f| {
thread::spawn(move|| {
f.invoke(());
});
})
}
#[test]
fn test_avoid_copying_the_body_join() {
avoid_copying_the_body(|f| {
let _ = thread::spawn(move|| {
f.invoke(())
}).join();
})
}
#[test]
fn test_child_doesnt_ref_parent() {
// If the child refcounts the parent task, this will stack overflow when
// climbing the task tree to dereference each ancestor. (See #1789)
// (well, it would if the constant were 8000+ - I lowered it to be more
// valgrind-friendly. try this at home, instead..!)
const GENERATIONS: u32 = 16;
fn child_no(x: u32) -> Thunk<'static> {
return Thunk::new(move|| {
if x < GENERATIONS {
thread::spawn(move|| child_no(x+1).invoke(()));
}
});
}
thread::spawn(|| child_no(0).invoke(()));
}
#[test]
fn test_simple_newsched_spawn() {
thread::spawn(move || {});
}
#[test]
fn test_try_panic_message_static_str() {
match thread::spawn(move|| {
panic!("static string");
}).join() {
Err(e) => {
type T = &'static str;
assert!(e.is::<T>());
assert_eq!(*e.downcast::<T>().unwrap(), "static string");
}
Ok(()) => panic!()
}
}
#[test]
fn test_try_panic_message_owned_str() {
match thread::spawn(move|| {
panic!("owned string".to_string());
}).join() {
Err(e) => {
type T = String;
assert!(e.is::<T>());
assert_eq!(*e.downcast::<T>().unwrap(), "owned string".to_string());
}
Ok(()) => panic!()
}
}
#[test]
fn test_try_panic_message_any() {
match thread::spawn(move|| {
panic!(box 413u16 as Box<Any + Send>);
}).join() {
Err(e) => {
type T = Box<Any + Send>;
assert!(e.is::<T>());
let any = e.downcast::<T>().unwrap();
assert!(any.is::<u16>());
assert_eq!(*any.downcast::<u16>().unwrap(), 413);
}
Ok(()) => panic!()
}
}
#[test]
fn test_try_panic_message_unit_struct() {
struct Juju;
match thread::spawn(move|| {
panic!(Juju)
}).join() {
Err(ref e) if e.is::<Juju>() => {}
Err(_) | Ok(()) => panic!()
}
}
#[test]
fn test_park_timeout_unpark_before() {
for _ in 0..10 {
thread::current().unpark();
thread::park_timeout(Duration::seconds(10_000_000));
}
}
#[test]
fn test_park_timeout_unpark_not_called() {
for _ in 0..10 {
thread::park_timeout(Duration::milliseconds(10));
}
}
#[test]
fn test_park_timeout_unpark_called_other_thread() {
use std::old_io;
for _ in 0..10 {
let th = thread::current();
let _guard = thread::spawn(move || {
old_io::timer::sleep(Duration::milliseconds(50));
th.unpark();
});
thread::park_timeout(Duration::seconds(10_000_000));
}
}
#[test]
fn sleep_smoke() {
thread::sleep(Duration::milliseconds(2));
thread::sleep(Duration::milliseconds(-2));
}
// NOTE: the corresponding test for stderr is in run-pass/task-stderr, due
// to the test harness apparently interfering with stderr configuration.
}