Rewrite threading infrastructure, introducing `Thunk` to represent

boxed `FnOnce` closures.

src/librustrt/at_exit_imp.rs

@@ -18,10 +18,11 @@
 use collections::vec::Vec;
 use core::atomic;
 use core::mem;
+use thunk::{Thunk};
 
 use exclusive::Exclusive;
 
-type Queue = Exclusive<Vec<proc():Send>>;
+type Queue = Exclusive<Vec<Thunk>>;
 
 static QUEUE: atomic::AtomicUint = atomic::INIT_ATOMIC_UINT;
 static RUNNING: atomic::AtomicBool = atomic::INIT_ATOMIC_BOOL;
@@ -34,7 +35,7 @@ pub fn init() {
     }
 }
 
-pub fn push(f: proc():Send) {
+pub fn push(f: Thunk) {
     unsafe {
         // Note that the check against 0 for the queue pointer is not atomic at
         // all with respect to `run`, meaning that this could theoretically be a
@@ -59,6 +60,6 @@ pub fn run() {
     };
 
     for to_run in cur.into_iter() {
-        to_run();
+        to_run.invoke(());
     }
 }

src/librustrt/lib.rs

@@ -46,6 +46,7 @@
 mod util;
 mod libunwind;
 mod stack_overflow;
+pub mod thunk;
 
 pub mod args;
 pub mod bookkeeping;
@@ -95,8 +96,8 @@ pub fn init(argc: int, argv: *const *const u8) {
 ///
 /// It is forbidden for procedures to register more `at_exit` handlers when they
 /// are running, and doing so will lead to a process abort.
-pub fn at_exit(f: proc():Send) {
-    at_exit_imp::push(f);
+pub fn at_exit<F:FnOnce()+Send>(f: F) {
+    at_exit_imp::push(thunk::Thunk::new(f));
 }
 
 /// One-time runtime cleanup.

src/librustrt/task.rs

@@ -21,6 +21,7 @@
 use core::atomic::{AtomicUint, SeqCst};
 use core::iter::{IteratorExt, Take};
 use core::kinds::marker;
+use core::ops::FnOnce;
 use core::mem;
 use core::ops::FnMut;
 use core::prelude::{Clone, Drop, Err, Iterator, None, Ok, Option, Send, Some};
@@ -34,6 +35,7 @@
 use unwind;
 use unwind::Unwinder;
 use collections::str::SendStr;
+use thunk::Thunk;
 
 /// State associated with Rust tasks.
 ///
@@ -67,7 +69,7 @@ enum TaskState {
 
 pub struct TaskOpts {
     /// Invoke this procedure with the result of the task when it finishes.
-    pub on_exit: Option<proc(Result): Send>,
+    pub on_exit: Option<Thunk<Result>>,
     /// A name for the task-to-be, for identification in panic messages
     pub name: Option<SendStr>,
     /// The size of the stack for the spawned task
@@ -92,7 +94,7 @@ pub enum BlockedTask {
 
 /// Per-task state related to task death, killing, panic, etc.
 pub struct Death {
-    pub on_exit: Option<proc(Result):Send>,
+    pub on_exit: Option<Thunk<Result>>,
     marker: marker::NoCopy,
 }
 
@@ -116,7 +118,13 @@ pub fn new(stack_bounds: Option<(uint, uint)>, stack_guard: Option<uint>) -> Tas
         }
     }
 
-    pub fn spawn(opts: TaskOpts, f: proc():Send) {
+    pub fn spawn<F>(opts: TaskOpts, f: F)
+        where F : FnOnce(), F : Send
+    {
+        Task::spawn_thunk(opts, Thunk::new(f))
+    }
+
+    fn spawn_thunk(opts: TaskOpts, f: Thunk) {
         let TaskOpts { name, stack_size, on_exit } = opts;
 
         let mut task = box Task::new(None, None);
@@ -138,7 +146,7 @@ pub fn spawn(opts: TaskOpts, f: proc():Send) {
         // 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).
-        Thread::spawn_stack(stack, proc() {
+        Thread::spawn_stack(stack, move|| {
             let something_around_the_top_of_the_stack = 1;
             let addr = &something_around_the_top_of_the_stack as *const int;
             let my_stack = addr as uint;
@@ -150,7 +158,7 @@ pub fn spawn(opts: TaskOpts, f: proc():Send) {
             task.stack_bounds = (my_stack - stack + 1024, my_stack);
 
             let mut f = Some(f);
-            drop(task.run(|| { f.take().unwrap()() }).destroy());
+            drop(task.run(|| { f.take().unwrap().invoke(()) }).destroy());
             drop(token);
         })
     }
@@ -241,7 +249,7 @@ fn cleanup(mut self: Box<Task>, result: Result) -> Box<Task> {
         //        reconsideration to whether it's a reasonable thing to let a
         //        task to do or not.
         match what_to_do {
-            Some(f) => { f(result) }
+            Some(f) => { f.invoke(result) }
             None => { drop(result) }
         }
 
@@ -500,14 +508,13 @@ mod test {
     use super::*;
     use std::prelude::*;
     use std::task;
-    use unwind;
 
     #[test]
     fn unwind() {
-        let result = task::try(proc()());
+        let result = task::try(move|| ());
         rtdebug!("trying first assert");
         assert!(result.is_ok());
-        let result = task::try::<()>(proc() panic!());
+        let result = task::try(move|| -> () panic!());
         rtdebug!("trying second assert");
         assert!(result.is_err());
     }

src/librustrt/thread.rs

@@ -22,6 +22,7 @@
 use core::mem;
 use core::uint;
 use libc;
+use thunk::{Thunk};
 
 use stack;
 use stack_overflow;
@@ -60,8 +61,8 @@ fn start_thread(main: *mut libc::c_void) -> imp::rust_thread_return {
     unsafe {
         stack::record_os_managed_stack_bounds(0, uint::MAX);
         let handler = stack_overflow::Handler::new();
-        let f: Box<proc()> = mem::transmute(main);
-        (*f)();
+        let f: Box<Thunk> = mem::transmute(main);
+        f.invoke(());
         drop(handler);
         mem::transmute(0 as imp::rust_thread_return)
     }
@@ -113,14 +114,17 @@ impl Thread<()> {
     /// to finish executing. This means that even if `join` is not explicitly
     /// called, when the `Thread` falls out of scope its destructor will block
     /// waiting for the OS thread.
-    pub fn start<T: Send>(main: proc():Send -> T) -> Thread<T> {
+    pub fn start<T,F>(main: F) -> Thread<T>
+        where T:Send, F:FnOnce() -> T, F:Send
+    {
         Thread::start_stack(DEFAULT_STACK_SIZE, main)
     }
 
     /// Performs the same functionality as `start`, but specifies an explicit
     /// stack size for the new thread.
-    pub fn start_stack<T: Send>(stack: uint, main: proc():Send -> T) -> Thread<T> {
-
+    pub fn start_stack<T, F>(stack: uint, main: F) -> Thread<T>
+        where T:Send, F:FnOnce() -> T, F:Send
+    {
         // We need the address of the packet to fill in to be stable so when
         // `main` fills it in it's still valid, so allocate an extra box to do
         // so.
@@ -128,8 +132,11 @@ pub fn start_stack<T: Send>(stack: uint, main: proc():Send -> T) -> Thread<T> {
         let packet2: *mut Option<T> = unsafe {
             *mem::transmute::<&Box<Option<T>>, *const *mut Option<T>>(&packet)
         };
-        let main = proc() unsafe { *packet2 = Some(main()); };
-        let native = unsafe { imp::create(stack, box main) };
+        let native = unsafe {
+            imp::create(stack, Thunk::new(move |:| {
+                *packet2 = Some(main.call_once(()));
+            }))
+        };
 
         Thread {
             native: native,
@@ -144,15 +151,19 @@ pub fn start_stack<T: Send>(stack: uint, main: proc():Send -> T) -> Thread<T> {
     /// This corresponds to creating threads in the 'detached' state on unix
     /// systems. Note that platforms may not keep the main program alive even if
     /// there are detached thread still running around.
-    pub fn spawn(main: proc():Send) {
+    pub fn spawn<F>(main: F)
+        where F : FnOnce() + Send
+    {
         Thread::spawn_stack(DEFAULT_STACK_SIZE, main)
     }
 
     /// Performs the same functionality as `spawn`, but explicitly specifies a
     /// stack size for the new thread.
-    pub fn spawn_stack(stack: uint, main: proc():Send) {
+    pub fn spawn_stack<F>(stack: uint, main: F)
+        where F : FnOnce() + Send
+    {
         unsafe {
-            let handle = imp::create(stack, box main);
+            let handle = imp::create(stack, Thunk::new(main));
             imp::detach(handle);
         }
     }
@@ -190,8 +201,6 @@ fn drop(&mut self) {
 #[cfg(windows)]
 #[allow(non_snake_case)]
 mod imp {
-    use core::prelude::*;
-
     use alloc::boxed::Box;
     use core::cmp;
     use core::mem;
@@ -200,6 +209,7 @@ mod imp {
     use libc::types::os::arch::extra::{LPSECURITY_ATTRIBUTES, SIZE_T, BOOL,
                                        LPVOID, DWORD, LPDWORD, HANDLE};
     use stack::RED_ZONE;
+    use thunk::Thunk;
 
     pub type rust_thread = HANDLE;
     pub type rust_thread_return = DWORD;
@@ -217,8 +227,9 @@ pub unsafe fn init() {
         }
     }
 
-    pub unsafe fn create(stack: uint, p: Box<proc():Send>) -> rust_thread {
-        let arg: *mut libc::c_void = mem::transmute(p);
+    pub unsafe fn create(stack: uint, p: Thunk) -> rust_thread {
+        let arg: *mut libc::c_void = mem::transmute(box p);
+
         // FIXME On UNIX, we guard against stack sizes that are too small but
         // that's because pthreads enforces that stacks are at least
         // PTHREAD_STACK_MIN bytes big.  Windows has no such lower limit, it's
@@ -234,7 +245,7 @@ pub unsafe fn create(stack: uint, p: Box<proc():Send>) -> rust_thread {
 
         if ret as uint == 0 {
             // be sure to not leak the closure
-            let _p: Box<proc():Send> = mem::transmute(arg);
+            let _p: Box<Thunk> = mem::transmute(arg);
             panic!("failed to spawn native thread: {}", ret);
         }
         return ret;
@@ -279,6 +290,7 @@ mod imp {
     use core::ptr;
     use libc::consts::os::posix01::{PTHREAD_CREATE_JOINABLE, PTHREAD_STACK_MIN};
     use libc;
+    use thunk::Thunk;
 
     use stack::RED_ZONE;
 
@@ -409,7 +421,7 @@ pub unsafe fn current() -> uint {
         }
     }
 
-    pub unsafe fn create(stack: uint, p: Box<proc():Send>) -> rust_thread {
+    pub unsafe fn create(stack: uint, p: Thunk) -> rust_thread {
         let mut native: libc::pthread_t = mem::zeroed();
         let mut attr: libc::pthread_attr_t = mem::zeroed();
         assert_eq!(pthread_attr_init(&mut attr), 0);
@@ -437,13 +449,13 @@ pub unsafe fn create(stack: uint, p: Box<proc():Send>) -> rust_thread {
             },
         };
 
-        let arg: *mut libc::c_void = mem::transmute(p);
+        let arg: *mut libc::c_void = mem::transmute(box p); // must box since sizeof(p)=2*uint
         let ret = pthread_create(&mut native, &attr, super::thread_start, arg);
         assert_eq!(pthread_attr_destroy(&mut attr), 0);
 
         if ret != 0 {
             // be sure to not leak the closure
-            let _p: Box<proc():Send> = mem::transmute(arg);
+            let _p: Box<Box<FnOnce()+Send>> = mem::transmute(arg);
             panic!("failed to spawn native thread: {}", ret);
         }
         native
@@ -531,17 +543,17 @@ mod tests {
     use super::Thread;
 
     #[test]
-    fn smoke() { Thread::start(proc (){}).join(); }
+    fn smoke() { Thread::start(move|| {}).join(); }
 
     #[test]
-    fn data() { assert_eq!(Thread::start(proc () { 1i }).join(), 1); }
+    fn data() { assert_eq!(Thread::start(move|| { 1i }).join(), 1); }
 
     #[test]
-    fn detached() { Thread::spawn(proc () {}) }
+    fn detached() { Thread::spawn(move|| {}) }
 
     #[test]
     fn small_stacks() {
-        assert_eq!(42i, Thread::start_stack(0, proc () 42i).join());
-        assert_eq!(42i, Thread::start_stack(1, proc () 42i).join());
+        assert_eq!(42i, Thread::start_stack(0, move|| 42i).join());
+        assert_eq!(42i, Thread::start_stack(1, move|| 42i).join());
     }
 }

src/librustrt/thunk.rs

+// 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.
+
+use alloc::boxed::Box;
+use core::kinds::Send;
+use core::ops::FnOnce;
+
+pub struct Thunk<A=(),R=()> {
+    invoke: Box<Invoke<A,R>+Send>
+}
+
+impl<R> Thunk<(),R> {
+    pub fn new<F>(func: F) -> Thunk<(),R>
+        where F : FnOnce() -> R, F : Send
+    {
+        Thunk::with_arg(move|: ()| func())
+    }
+}
+
+impl<A,R> Thunk<A,R> {
+    pub fn with_arg<F>(func: F) -> Thunk<A,R>
+        where F : FnOnce(A) -> R, F : Send
+    {
+        Thunk {
+            invoke: box func
+        }
+    }
+
+    pub fn invoke(self, arg: A) -> R {
+        self.invoke.invoke(arg)
+    }
+}
+
+pub trait Invoke<A=(),R=()> {
+    fn invoke(self: Box<Self>, arg: A) -> R;
+}
+
+impl<A,R,F> Invoke<A,R> for F
+    where F : FnOnce(A) -> R
+{
+    fn invoke(self: Box<F>, arg: A) -> R {
+        let f = *self;
+        f(arg)
+    }
+}

src/libstd/lib.rs

@@ -171,6 +171,8 @@
 
 pub use unicode::char;
 
+pub use rustrt::thunk;
+
 /* Exported macros */
 
 pub mod macros;

src/libstd/rt/mod.rs

@@ -52,6 +52,7 @@
 use failure;
 use rustrt;
 use os;
+use thunk::Thunk;
 
 // Reexport some of our utilities which are expected by other crates.
 pub use self::util::{default_sched_threads, min_stack, running_on_valgrind};
@@ -87,10 +88,10 @@ pub fn init(argc: int, argv: *const *const u8) {
 #[lang = "start"]
 fn lang_start(main: *const u8, argc: int, argv: *const *const u8) -> int {
     use mem;
-    start(argc, argv, proc() {
+    start(argc, argv, Thunk::new(move|| {
         let main: extern "Rust" fn() = unsafe { mem::transmute(main) };
         main();
-    })
+    }))
 }
 
 /// Executes the given procedure after initializing the runtime with the given
@@ -102,7 +103,7 @@ fn lang_start(main: *const u8, argc: int, argv: *const *const u8) -> int {
 ///
 /// This function will only return once *all* native threads in the system have
 /// exited.
-pub fn start(argc: int, argv: *const *const u8, main: proc()) -> int {
+pub fn start(argc: int, argv: *const *const u8, main: Thunk) -> int {
     use prelude::*;
     use rt;
     use rustrt::task::Task;
@@ -144,7 +145,7 @@ pub fn start(argc: int, argv: *const *const u8, main: proc()) -> int {
         unsafe {
             rustrt::stack::record_os_managed_stack_bounds(my_stack_bottom, my_stack_top);
         }
-        (main.take().unwrap())();
+        (main.take().unwrap()).invoke(());
         exit_code = Some(os::get_exit_status());
     }).destroy());
     unsafe { rt::cleanup(); }

src/libstd/sync/future.rs

@@ -17,7 +17,7 @@
 //! use std::sync::Future;
 //! # fn fib(n: uint) -> uint {42};
 //! # fn make_a_sandwich() {};
-//! let mut delayed_fib = Future::spawn(proc() { fib(5000) });
+//! let mut delayed_fib = Future::spawn(move|| { fib(5000) });
 //! make_a_sandwich();
 //! println!("fib(5000) = {}", delayed_fib.get())
 //! ```
@@ -30,6 +30,7 @@
 use self::FutureState::*;
 use comm::{Receiver, channel};
 use task::spawn;
+use thunk::{Thunk};
 
 /// A type encapsulating the result of a computation which may not be complete
 pub struct Future<A> {
@@ -37,7 +38,7 @@ pub struct Future<A> {
 }
 
 enum FutureState<A> {
-    Pending(proc():Send -> A),
+    Pending(Thunk<(),A>),
     Evaluating,
     Forced(A)
 }
@@ -78,7 +79,7 @@ pub fn get_ref<'a>(&'a mut self) -> &'a A {
                 match replace(&mut self.state, Evaluating) {
                     Forced(_) | Evaluating => panic!("Logic error."),
                     Pending(f) => {
-                        self.state = Forced(f());
+                        self.state = Forced(f.invoke(()));
                         self.get_ref()
                     }
                 }
@@ -97,7 +98,9 @@ pub fn from_value(val: A) -> Future<A> {
         Future {state: Forced(val)}
     }
 
-    pub fn from_fn(f: proc():Send -> A) -> Future<A> {
+    pub fn from_fn<F>(f: F) -> Future<A>
+        where F : FnOnce() -> A, F : Send
+    {
         /*!
          * Create a future from a function.
          *
@@ -106,7 +109,7 @@ pub fn from_fn(f: proc():Send -> A) -> Future<A> {
          * function. It is not spawned into another task.
          */
 
-        Future {state: Pending(f)}
+        Future {state: Pending(Thunk::new(f))}
     }
 }
 
@@ -119,12 +122,14 @@ pub fn from_receiver(rx: Receiver<A>) -> Future<A> {
          * waiting for the result to be received on the port.
          */
 
-        Future::from_fn(proc() {
+        Future::from_fn(move|:| {
             rx.recv()
         })
     }
 
-    pub fn spawn(blk: proc():Send -> A) -> Future<A> {
+    pub fn spawn<F>(blk: F) -> Future<A>
+        where F : FnOnce() -> A, F : Send
+    {
         /*!
          * Create a future from a unique closure.
          *
@@ -134,7 +139,7 @@ pub fn spawn(blk: proc():Send -> A) -> Future<A> {
 
         let (tx, rx) = channel();
 
-        spawn(proc() {
+        spawn(move |:| {
             // Don't panic if the other end has hung up
             let _ = tx.send_opt(blk());
         });
@@ -166,7 +171,7 @@ fn test_from_receiver() {
 
     #[test]
     fn test_from_fn() {
-        let mut f = Future::from_fn(proc() "brail".to_string());
+        let mut f = Future::from_fn(move|| "brail".to_string());
         assert_eq!(f.get(), "brail");
     }
 
@@ -190,14 +195,14 @@ fn test_get_ref_method() {
 
     #[test]
     fn test_spawn() {
-        let mut f = Future::spawn(proc() "bale".to_string());
+        let mut f = Future::spawn(move|| "bale".to_string());
         assert_eq!(f.get(), "bale");
     }
 
     #[test]
     #[should_fail]
     fn test_future_panic() {
-        let mut f = Future::spawn(proc() panic!());
+        let mut f = Future::spawn(move|| panic!());
         let _x: String = f.get();
     }
 
@@ -205,8 +210,8 @@ fn test_future_panic() {
     fn test_sendable_future() {
         let expected = "schlorf";
         let (tx, rx) = channel();
-        let f = Future::spawn(proc() { expected });
-        task::spawn(proc() {
+        let f = Future::spawn(move|| { expected });
+        task::spawn(move|| {
             let mut f = f;
             tx.send(f.get());
         });

src/libstd/sync/task_pool.rs

@@ -72,7 +72,7 @@ pub struct TaskPool {
     //
     // This is the only such Sender, so when it is dropped all subtasks will
     // quit.
-    jobs: Sender<proc(): Send>
+    jobs: Sender<Thunk>
 }
 
 impl TaskPool {
@@ -84,7 +84,7 @@ impl TaskPool {
     pub fn new(tasks: uint) -> TaskPool {
         assert!(tasks >= 1);
 
-        let (tx, rx) = channel::<proc(): Send>();
+        let (tx, rx) = channel::<Thunk>();
         let rx = Arc::new(Mutex::new(rx));
 
         // Taskpool tasks.
@@ -96,13 +96,15 @@ pub fn new(tasks: uint) -> TaskPool {
     }
 
     /// Executes the function `job` on a task in the pool.
-    pub fn execute(&self, job: proc():Send) {
-        self.jobs.send(job);
+    pub fn execute<F>(&self, job: F)
+        where F : FnOnce(), F : Send
+    {
+        self.jobs.send(Thunk::new(job));
     }
 }
 
-fn spawn_in_pool(jobs: Arc<Mutex<Receiver<proc(): Send>>>) {
-    spawn(proc() {
+fn spawn_in_pool(jobs: Arc<Mutex<Receiver<Thunk>>>) {
+    spawn(move |:| {
         // Will spawn a new task on panic unless it is cancelled.
         let sentinel = Sentinel::new(&jobs);
 
@@ -115,7 +117,7 @@ fn spawn_in_pool(jobs: Arc<Mutex<Receiver<proc(): Send>>>) {
             };
 
             match message {
-                Ok(job) => job(),
+                Ok(job) => job.invoke(()),
 
                 // The Taskpool was dropped.
                 Err(..) => break

src/libstd/sys/unix/process.rs

@@ -531,8 +531,11 @@ pub fn try_wait(&self) -> Option<ProcessExit> {
     }
 }
 
-fn with_argv<T>(prog: &CString, args: &[CString],
-                cb: proc(*const *const libc::c_char) -> T) -> T {
+fn with_argv<T,F>(prog: &CString, args: &[CString],
+                  cb: F)
+                  -> T
+    where F : FnOnce(*const *const libc::c_char) -> T
+{
     let mut ptrs: Vec<*const libc::c_char> = Vec::with_capacity(args.len()+1);
 
     // Convert the CStrings into an array of pointers. Note: the
@@ -549,9 +552,12 @@ fn with_argv<T>(prog: &CString, args: &[CString],
     cb(ptrs.as_ptr())
 }
 
-fn with_envp<K, V, T>(env: Option<&collections::HashMap<K, V>>,
-                      cb: proc(*const c_void) -> T) -> T
-    where K: BytesContainer + Eq + Hash, V: BytesContainer
+fn with_envp<K,V,T,F>(env: Option<&collections::HashMap<K, V>>,
+                      cb: F)
+                      -> T
+    where F : FnOnce(*const c_void) -> T,
+          K : BytesContainer + Eq + Hash,
+          V : BytesContainer
 {
     // On posixy systems we can pass a char** for envp, which is a
     // null-terminated array of "k=v\0" strings. Since we must create

src/libstd/task.rs

@@ -35,7 +35,7 @@
 //! ## Example
 //!
 //! ```rust
-//! spawn(proc() {
+//! spawn(move|| {
 //!     println!("Hello, World!");
 //! })
 //! ```
@@ -47,6 +47,7 @@
 use borrow::IntoCow;
 use boxed::Box;
 use comm::channel;
+use core::ops::FnOnce;
 use io::{Writer, stdio};
 use kinds::{Send, marker};
 use option::Option;
@@ -57,6 +58,7 @@
 use rustrt::task;
 use str::SendStr;
 use string::{String, ToString};
+use thunk::{Thunk};
 use sync::Future;
 
 /// The task builder type.
@@ -80,7 +82,7 @@ pub struct TaskBuilder {
     // Task-local stderr
     stderr: Option<Box<Writer + Send>>,
     // Optionally wrap the eventual task body
-    gen_body: Option<proc(v: proc():Send):Send -> proc():Send>,
+    gen_body: Option<Thunk<Thunk, Thunk>>,
     nocopy: marker::NoCopy,
 }
 
@@ -129,41 +131,46 @@ pub fn stderr(mut self, stderr: Box<Writer + Send>) -> TaskBuilder {
     }
 
     // Where spawning actually happens (whether yielding a future or not)
-    fn spawn_internal(self, f: proc():Send,
-                      on_exit: Option<proc(Result<(), Box<Any + Send>>):Send>) {
+    fn spawn_internal(
+        self,
+        f: Thunk,
+        on_exit: Option<Thunk<task::Result>>)
+    {
         let TaskBuilder {
             name, stack_size, stdout, stderr, mut gen_body, nocopy: _
         } = self;
+
         let f = match gen_body.take() {
-            Some(gen) => gen(f),
+            Some(gen) => gen.invoke(f),
             None => f
         };
+
         let opts = task::TaskOpts {
             on_exit: on_exit,
             name: name,
             stack_size: stack_size,
         };
         if stdout.is_some() || stderr.is_some() {
-            Task::spawn(opts, proc() {
+            Task::spawn(opts, move|:| {
                 let _ = stdout.map(stdio::set_stdout);
                 let _ = stderr.map(stdio::set_stderr);
-                f();
-            })
+                f.invoke(());
+            });
         } else {
-            Task::spawn(opts, f)
+            Task::spawn(opts, move|:| f.invoke(()))
         }
     }
 
     /// Creates and executes a new child task.
     ///
     /// Sets up a new task with its own call stack and schedules it to run
-    /// the provided proc. The task has the properties and behavior
+    /// the provided function. The task has the properties and behavior
     /// specified by the `TaskBuilder`.
-    pub fn spawn(self, f: proc():Send) {
-        self.spawn_internal(f, None)
+    pub fn spawn<F:FnOnce()+Send>(self, f: F) {
+        self.spawn_internal(Thunk::new(f), None)
     }
 
-    /// Execute a proc in a newly-spawned task and return a future representing
+    /// Execute a function in a newly-spawned task and return a future representing
     /// the task's result. The task has the properties and behavior
     /// specified by the `TaskBuilder`.
     ///
@@ -178,20 +185,22 @@ pub fn spawn(self, f: proc():Send) {
     /// `result::Result::Err` containing the argument to `panic!(...)` as an
     /// `Any` trait object.
     #[experimental = "Futures are experimental."]
-    pub fn try_future<T:Send>(self, f: proc():Send -> T)
-                              -> Future<Result<T, Box<Any + Send>>> {
-        // currently, the on_exit proc provided by librustrt only works for unit
+    pub fn try_future<T:Send,F:FnOnce()->(T)+Send>(self, f: F)
+                                                   -> Future<Result<T, Box<Any + Send>>> {
+        // currently, the on_exit fn provided by librustrt only works for unit
         // results, so we use an additional side-channel to communicate the
         // result.
 
         let (tx_done, rx_done) = channel(); // signal that task has exited
         let (tx_retv, rx_retv) = channel(); // return value from task
 
-        let on_exit = proc(res) { let _ = tx_done.send_opt(res); };
-        self.spawn_internal(proc() { let _ = tx_retv.send_opt(f()); },
+        let on_exit: Thunk<task::Result> = Thunk::with_arg(move |: res: task::Result| {
+            let _ = tx_done.send_opt(res);
+        });
+        self.spawn_internal(Thunk::new(move |:| { let _ = tx_retv.send_opt(f()); }),
                             Some(on_exit));
 
-        Future::from_fn(proc() {
+        Future::from_fn(move|:| {
             rx_done.recv().map(|_| rx_retv.recv())
         })
     }
@@ -199,7 +208,9 @@ pub fn try_future<T:Send>(self, f: proc():Send -> T)
     /// Execute a function in a newly-spawnedtask and block until the task
     /// completes or panics. Equivalent to `.try_future(f).unwrap()`.
     #[unstable = "Error type may change."]
-    pub fn try<T:Send>(self, f: proc():Send -> T) -> Result<T, Box<Any + Send>> {
+    pub fn try<T,F>(self, f: F) -> Result<T, Box<Any + Send>>
+        where F : FnOnce() -> T, F : Send, T : Send
+    {
         self.try_future(f).into_inner()
     }
 }
@@ -212,7 +223,7 @@ pub fn try<T:Send>(self, f: proc():Send -> T) -> Result<T, Box<Any + Send>> {
 /// the provided unique closure.
 ///
 /// This function is equivalent to `TaskBuilder::new().spawn(f)`.
-pub fn spawn(f: proc(): Send) {
+pub fn spawn<F:FnOnce()+Send>(f: F) {
     TaskBuilder::new().spawn(f)
 }
 
@@ -221,7 +232,9 @@ pub fn spawn(f: proc(): Send) {
 ///
 /// This is equivalent to `TaskBuilder::new().try`.
 #[unstable = "Error type may change."]
-pub fn try<T: Send>(f: proc(): Send -> T) -> Result<T, Box<Any + Send>> {
+pub fn try<T,F>(f: F) -> Result<T, Box<Any + Send>>
+    where T : Send, F : FnOnce() -> T, F : Send
+{
     TaskBuilder::new().try(f)
 }
 
@@ -230,11 +243,12 @@ pub fn try<T: Send>(f: proc(): Send -> T) -> Result<T, Box<Any + Send>> {
 ///
 /// This is equivalent to `TaskBuilder::new().try_future`.
 #[experimental = "Futures are experimental."]
-pub fn try_future<T:Send>(f: proc():Send -> T) -> Future<Result<T, Box<Any + Send>>> {
+pub fn try_future<T,F>(f: F) -> Future<Result<T, Box<Any + Send>>>
+    where T:Send, F:FnOnce()->T, F:Send
+{
     TaskBuilder::new().try_future(f)
 }
 
-
 /* Lifecycle functions */
 
 /// Read the name of the current task.
@@ -274,6 +288,8 @@ mod test {
     use result;
     use std::io::{ChanReader, ChanWriter};
     use string::String;
+    use thunk::Thunk;
+    use prelude::*;
     use super::*;
 
     // !!! These tests are dangerous. If something is buggy, they will hang, !!!
@@ -281,28 +297,28 @@ mod test {
 
     #[test]
     fn test_unnamed_task() {
-        try(proc() {
+        try(move|| {
             assert!(name().is_none());
         }).map_err(|_| ()).unwrap();
     }
 
     #[test]
     fn test_owned_named_task() {
-        TaskBuilder::new().named("ada lovelace".to_string()).try(proc() {
+        TaskBuilder::new().named("ada lovelace".to_string()).try(move|| {
             assert!(name().unwrap() == "ada lovelace");
         }).map_err(|_| ()).unwrap();
     }
 
     #[test]
     fn test_static_named_task() {
-        TaskBuilder::new().named("ada lovelace").try(proc() {
+        TaskBuilder::new().named("ada lovelace").try(move|| {
             assert!(name().unwrap() == "ada lovelace");
         }).map_err(|_| ()).unwrap();
     }
 
     #[test]
     fn test_send_named_task() {
-        TaskBuilder::new().named("ada lovelace".into_cow()).try(proc() {
+        TaskBuilder::new().named("ada lovelace".into_cow()).try(move|| {
             assert!(name().unwrap() == "ada lovelace");
         }).map_err(|_| ()).unwrap();
     }
@@ -310,7 +326,7 @@ fn test_send_named_task() {
     #[test]
     fn test_run_basic() {
         let (tx, rx) = channel();
-        TaskBuilder::new().spawn(proc() {
+        TaskBuilder::new().spawn(move|| {
             tx.send(());
         });
         rx.recv();
@@ -318,10 +334,10 @@ fn test_run_basic() {
 
     #[test]
     fn test_try_future() {
-        let result = TaskBuilder::new().try_future(proc() {});
+        let result = TaskBuilder::new().try_future(move|| {});
         assert!(result.unwrap().is_ok());
 
-        let result = TaskBuilder::new().try_future(proc() -> () {
+        let result = TaskBuilder::new().try_future(move|| -> () {
             panic!();
         });
         assert!(result.unwrap().is_err());
@@ -329,7 +345,7 @@ fn test_try_future() {
 
     #[test]
     fn test_try_success() {
-        match try(proc() {
+        match try(move|| {
             "Success!".to_string()
         }).as_ref().map(|s| s.as_slice()) {
             result::Result::Ok("Success!") => (),
@@ -339,7 +355,7 @@ fn test_try_success() {
 
     #[test]
     fn test_try_panic() {
-        match try(proc() {
+        match try(move|| {
             panic!()
         }) {
             result::Result::Err(_) => (),
@@ -355,7 +371,7 @@ fn test_spawn_sched() {
 
         fn f(i: int, tx: Sender<()>) {
             let tx = tx.clone();
-            spawn(proc() {
+            spawn(move|| {
                 if i == 0 {
                     tx.send(());
                 } else {
@@ -372,8 +388,8 @@ fn f(i: int, tx: Sender<()>) {
     fn test_spawn_sched_childs_on_default_sched() {
         let (tx, rx) = channel();
 
-        spawn(proc() {
-            spawn(proc() {
+        spawn(move|| {
+            spawn(move|| {
                 tx.send(());
             });
         });
@@ -382,17 +398,17 @@ fn test_spawn_sched_childs_on_default_sched() {
     }
 
     fn avoid_copying_the_body<F>(spawnfn: F) where
-        F: FnOnce(proc():Send),
+        F: FnOnce(Thunk),
     {
         let (tx, rx) = channel::<uint>();
 
         let x = box 1;
         let x_in_parent = (&*x) as *const int as uint;
 
-        spawnfn(proc() {
+        spawnfn(Thunk::new(move|| {
             let x_in_child = (&*x) as *const int as uint;
             tx.send(x_in_child);
-        });
+        }));
 
         let x_in_child = rx.recv();
         assert_eq!(x_in_parent, x_in_child);
@@ -400,25 +416,21 @@ fn avoid_copying_the_body<F>(spawnfn: F) where
 
     #[test]
     fn test_avoid_copying_the_body_spawn() {
-        avoid_copying_the_body(spawn);
+        avoid_copying_the_body(|t| spawn(move|| t.invoke(())));
     }
 
     #[test]
     fn test_avoid_copying_the_body_task_spawn() {
         avoid_copying_the_body(|f| {
             let builder = TaskBuilder::new();
-            builder.spawn(proc() {
-                f();
-            });
+            builder.spawn(move|| f.invoke(()));
         })
     }
 
     #[test]
     fn test_avoid_copying_the_body_try() {
         avoid_copying_the_body(|f| {
-            let _ = try(proc() {
-                f()
-            });
+            let _ = try(move|| f.invoke(()));
         })
     }
 
@@ -429,24 +441,24 @@ fn test_child_doesnt_ref_parent() {
         // (well, it would if the constant were 8000+ - I lowered it to be more
         // valgrind-friendly. try this at home, instead..!)
         static GENERATIONS: uint = 16;
-        fn child_no(x: uint) -> proc(): Send {
-            return proc() {
+        fn child_no(x: uint) -> Thunk {
+            return Thunk::new(move|| {
                 if x < GENERATIONS {
-                    TaskBuilder::new().spawn(child_no(x+1));
+                    TaskBuilder::new().spawn(move|| child_no(x+1).invoke(()));
                 }
-            }
+            });
         }
-        TaskBuilder::new().spawn(child_no(0));
+        TaskBuilder::new().spawn(|| child_no(0).invoke(()));
     }
 
     #[test]
     fn test_simple_newsched_spawn() {
-        spawn(proc()())
+        spawn(move|| ())
     }
 
     #[test]
     fn test_try_panic_message_static_str() {
-        match try(proc() {
+        match try(move|| {
             panic!("static string");
         }) {
             Err(e) => {
@@ -460,7 +472,7 @@ fn test_try_panic_message_static_str() {
 
     #[test]
     fn test_try_panic_message_owned_str() {
-        match try(proc() {
+        match try(move|| {
             panic!("owned string".to_string());
         }) {
             Err(e) => {
@@ -474,7 +486,7 @@ fn test_try_panic_message_owned_str() {
 
     #[test]
     fn test_try_panic_message_any() {
-        match try(proc() {
+        match try(move|| {
             panic!(box 413u16 as Box<Any + Send>);
         }) {
             Err(e) => {
@@ -492,7 +504,7 @@ fn test_try_panic_message_any() {
     fn test_try_panic_message_unit_struct() {
         struct Juju;
 
-        match try(proc() {
+        match try(move|| {
             panic!(Juju)
         }) {
             Err(ref e) if e.is::<Juju>() => {}
@@ -507,7 +519,7 @@ fn test_stdout() {
         let stdout = ChanWriter::new(tx);
 
         let r = TaskBuilder::new().stdout(box stdout as Box<Writer + Send>)
-                                  .try(proc() {
+                                  .try(move|| {
                 print!("Hello, world!");
             });
         assert!(r.is_ok());
@@ -527,7 +539,7 @@ fn task_abort_no_kill_runtime() {
     use mem;
 
     let tb = TaskBuilder::new();
-    let rx = tb.try_future(proc() {});
+    let rx = tb.try_future(move|| {});
     mem::drop(rx);
     timer::sleep(Duration::milliseconds(1000));
 }