Runtime removal: refactor process

This patch continues the runtime removal by moving and refactoring the
process implementation into the new `sys` module.

Because this eliminates APIs in `libnative` and `librustrt`, it is a:

[breaking-change]

This functionality is likely to be available publicly, in some form,
from `std` in the future.

10 files changed, 1250 insertions, 176 deletions

diff --git a/src/libnative/io/mod.rs b/src/libnative/io/mod.rs
index 1d0b9f40d07..29370dee88b 100644
--- a/src/libnative/io/mod.rs
+++ b/src/libnative/io/mod.rs
@@ -29,13 +29,6 @@ use std::os;
 use std::rt::rtio::{mod, IoResult, IoError};
 use std::num;
 
-// Local re-exports
-pub use self::process::Process;
-
-// Native I/O implementations
-pub mod process;
-mod util;
-
 #[cfg(any(target_os = "macos",
           target_os = "ios",
           target_os = "freebsd",
@@ -123,19 +116,6 @@ impl rtio::IoFactory for IoFactory {
     fn timer_init(&mut self) -> IoResult<Box<rtio::RtioTimer + Send>> {
         timer::Timer::new().map(|t| box t as Box<rtio::RtioTimer + Send>)
     }
-    fn spawn(&mut self, cfg: rtio::ProcessConfig)
-            -> IoResult<(Box<rtio::RtioProcess + Send>,
-                         Vec<Option<Box<rtio::RtioPipe + Send>>>)> {
-        process::Process::spawn(cfg).map(|(p, io)| {
-            (box p as Box<rtio::RtioProcess + Send>,
-             io.into_iter().map(|p| p.map(|p| {
-                 box p as Box<rtio::RtioPipe + Send>
-             })).collect())
-        })
-    }
-    fn kill(&mut self, pid: libc::pid_t, signum: int) -> IoResult<()> {
-        process::Process::kill(pid, signum)
-    }
     #[cfg(unix)]
     fn tty_open(&mut self, fd: c_int, _readable: bool)
                 -> IoResult<Box<rtio::RtioTTY + Send>> {
diff --git a/src/librustrt/rtio.rs b/src/librustrt/rtio.rs
index 3ebfcaea687..cdcefc2088e 100644
--- a/src/librustrt/rtio.rs
+++ b/src/librustrt/rtio.rs
@@ -46,61 +46,6 @@ pub trait RemoteCallback {
     fn fire(&mut self);
 }
 
-/// Data needed to spawn a process. Serializes the `std::io::process::Command`
-/// builder.
-pub struct ProcessConfig<'a> {
-    /// Path to the program to run.
-    pub program: &'a CString,
-
-    /// Arguments to pass to the program (doesn't include the program itself).
-    pub args: &'a [CString],
-
-    /// Optional environment to specify for the program. If this is None, then
-    /// it will inherit the current process's environment.
-    pub env: Option<&'a [(&'a CString, &'a CString)]>,
-
-    /// Optional working directory for the new process. If this is None, then
-    /// the current directory of the running process is inherited.
-    pub cwd: Option<&'a CString>,
-
-    /// Configuration for the child process's stdin handle (file descriptor 0).
-    /// This field defaults to `CreatePipe(true, false)` so the input can be
-    /// written to.
-    pub stdin: StdioContainer,
-
-    /// Configuration for the child process's stdout handle (file descriptor 1).
-    /// This field defaults to `CreatePipe(false, true)` so the output can be
-    /// collected.
-    pub stdout: StdioContainer,
-
-    /// Configuration for the child process's stdout handle (file descriptor 2).
-    /// This field defaults to `CreatePipe(false, true)` so the output can be
-    /// collected.
-    pub stderr: StdioContainer,
-
-    /// Any number of streams/file descriptors/pipes may be attached to this
-    /// process. This list enumerates the file descriptors and such for the
-    /// process to be spawned, and the file descriptors inherited will start at
-    /// 3 and go to the length of this array. The first three file descriptors
-    /// (stdin/stdout/stderr) are configured with the `stdin`, `stdout`, and
-    /// `stderr` fields.
-    pub extra_io: &'a [StdioContainer],
-
-    /// Sets the child process's user id. This translates to a `setuid` call in
-    /// the child process. Setting this value on windows will cause the spawn to
-    /// fail. Failure in the `setuid` call on unix will also cause the spawn to
-    /// fail.
-    pub uid: Option<uint>,
-
-    /// Similar to `uid`, but sets the group id of the child process. This has
-    /// the same semantics as the `uid` field.
-    pub gid: Option<uint>,
-
-    /// If true, the child process is spawned in a detached state. On unix, this
-    /// means that the child is the leader of a new process group.
-    pub detach: bool,
-}
-
 pub struct LocalIo<'a> {
     factory: &'a mut IoFactory+'a,
 }
@@ -170,10 +115,6 @@ impl<'a> LocalIo<'a> {
 
 pub trait IoFactory {
     fn timer_init(&mut self) -> IoResult<Box<RtioTimer + Send>>;
-    fn spawn(&mut self, cfg: ProcessConfig)
-            -> IoResult<(Box<RtioProcess + Send>,
-                         Vec<Option<Box<RtioPipe + Send>>>)>;
-    fn kill(&mut self, pid: libc::pid_t, signal: int) -> IoResult<()>;
     fn tty_open(&mut self, fd: c_int, readable: bool)
             -> IoResult<Box<RtioTTY + Send>>;
 }
@@ -184,13 +125,6 @@ pub trait RtioTimer {
     fn period(&mut self, msecs: u64, cb: Box<Callback + Send>);
 }
 
-pub trait RtioProcess {
-    fn id(&self) -> libc::pid_t;
-    fn kill(&mut self, signal: int) -> IoResult<()>;
-    fn wait(&mut self) -> IoResult<ProcessExit>;
-    fn set_timeout(&mut self, timeout: Option<u64>);
-}
-
 pub trait RtioPipe {
     fn read(&mut self, buf: &mut [u8]) -> IoResult<uint>;
     fn write(&mut self, buf: &[u8]) -> IoResult<()>;
diff --git a/src/libstd/io/process.rs b/src/libstd/io/process.rs
index 698e0a3460f..d71bab0b48f 100644
--- a/src/libstd/io/process.rs
+++ b/src/libstd/io/process.rs
@@ -20,14 +20,17 @@ use os;
 use io::{IoResult, IoError};
 use io;
 use libc;
-use mem;
-use rt::rtio::{RtioProcess, ProcessConfig, IoFactory, LocalIo};
-use rt::rtio;
 use c_str::CString;
 use collections::HashMap;
 use hash::Hash;
 #[cfg(windows)]
 use std::hash::sip::SipState;
+use io::pipe::{PipeStream, PipePair};
+use path::BytesContainer;
+
+use sys;
+use sys::fs::FileDesc;
+use sys::process::Process as ProcessImp;
 
 /// Signal a process to exit, without forcibly killing it. Corresponds to
 /// SIGTERM on unix platforms.
@@ -62,24 +65,29 @@ use std::hash::sip::SipState;
 /// assert!(child.wait().unwrap().success());
 /// ```
 pub struct Process {
-    handle: Box<RtioProcess + Send>,
+    handle: ProcessImp,
     forget: bool,
 
+    /// None until wait() is called.
+    exit_code: Option<ProcessExit>,
+
+    /// Manually delivered signal
+    exit_signal: Option<int>,
+
+    /// Deadline after which wait() will return
+    deadline: u64,
+
     /// Handle to the child's stdin, if the `stdin` field of this process's
     /// `ProcessConfig` was `CreatePipe`. By default, this handle is `Some`.
-    pub stdin: Option<io::PipeStream>,
+    pub stdin: Option<PipeStream>,
 
     /// Handle to the child's stdout, if the `stdout` field of this process's
     /// `ProcessConfig` was `CreatePipe`. By default, this handle is `Some`.
-    pub stdout: Option<io::PipeStream>,
+    pub stdout: Option<PipeStream>,
 
     /// Handle to the child's stderr, if the `stderr` field of this process's
     /// `ProcessConfig` was `CreatePipe`. By default, this handle is `Some`.
-    pub stderr: Option<io::PipeStream>,
-
-    /// Extra I/O handles as configured by the original `ProcessConfig` when
-    /// this process was created. This is by default empty.
-    pub extra_io: Vec<Option<io::PipeStream>>,
+    pub stderr: Option<PipeStream>,
 }
 
 /// A representation of environment variable name
@@ -130,6 +138,13 @@ impl PartialEq for EnvKey {
     }
 }
 
+impl BytesContainer for EnvKey {
+    fn container_as_bytes<'a>(&'a self) -> &'a [u8] {
+        let &EnvKey(ref k) = self;
+        k.container_as_bytes()
+    }
+}
+
 /// A HashMap representation of environment variables.
 pub type EnvMap = HashMap<EnvKey, CString>;
 
@@ -160,7 +175,6 @@ pub struct Command {
     stdin: StdioContainer,
     stdout: StdioContainer,
     stderr: StdioContainer,
-    extra_io: Vec<StdioContainer>,
     uid: Option<uint>,
     gid: Option<uint>,
     detach: bool,
@@ -194,7 +208,6 @@ impl Command {
             stdin: CreatePipe(true, false),
             stdout: CreatePipe(false, true),
             stderr: CreatePipe(false, true),
-            extra_io: Vec::new(),
             uid: None,
             gid: None,
             detach: false,
@@ -281,14 +294,6 @@ impl Command {
         self.stderr = cfg;
         self
     }
-    /// Attaches a stream/file descriptor/pipe to the child process. Inherited
-    /// file descriptors are numbered consecutively, starting at 3; the first
-    /// three file descriptors (stdin/stdout/stderr) are configured with the
-    /// `stdin`, `stdout`, and `stderr` methods.
-    pub fn extra_io<'a>(&'a mut self, cfg: StdioContainer) -> &'a mut Command {
-        self.extra_io.push(cfg);
-        self
-    }
 
     /// Sets the child process's user id. This translates to a `setuid` call in
     /// the child process. Setting this value on windows will cause the spawn to
@@ -315,50 +320,23 @@ impl Command {
 
     /// Executes the command as a child process, which is returned.
     pub fn spawn(&self) -> IoResult<Process> {
-        fn to_rtio(p: StdioContainer) -> rtio::StdioContainer {
-            match p {
-                Ignored => rtio::Ignored,
-                InheritFd(fd) => rtio::InheritFd(fd),
-                CreatePipe(a, b) => rtio::CreatePipe(a, b),
-            }
-        }
-        let extra_io: Vec<rtio::StdioContainer> =
-            self.extra_io.iter().map(|x| to_rtio(*x)).collect();
-        LocalIo::maybe_raise(|io| {
-            let env = match self.env {
-                None => None,
-                Some(ref env_map) =>
-                    Some(env_map.iter()
-                                .map(|(&EnvKey(ref key), val)| (key, val))
-                                .collect::<Vec<_>>())
-            };
-            let cfg = ProcessConfig {
-                program: &self.program,
-                args: self.args.as_slice(),
-                env: env.as_ref().map(|e| e.as_slice()),
-                cwd: self.cwd.as_ref(),
-                stdin: to_rtio(self.stdin),
-                stdout: to_rtio(self.stdout),
-                stderr: to_rtio(self.stderr),
-                extra_io: extra_io.as_slice(),
-                uid: self.uid,
-                gid: self.gid,
-                detach: self.detach,
-            };
-            io.spawn(cfg).map(|(p, io)| {
-                let mut io = io.into_iter().map(|p| {
-                    p.map(|p| io::PipeStream::new(p))
-                });
-                Process {
-                    handle: p,
-                    forget: false,
-                    stdin: io.next().unwrap(),
-                    stdout: io.next().unwrap(),
-                    stderr: io.next().unwrap(),
-                    extra_io: io.collect(),
-                }
+        let (their_stdin, our_stdin) = try!(setup_io(self.stdin));
+        let (their_stdout, our_stdout) = try!(setup_io(self.stdout));
+        let (their_stderr, our_stderr) = try!(setup_io(self.stderr));
+
+        match ProcessImp::spawn(self, their_stdin, their_stdout, their_stderr) {
+            Err(e) => Err(e),
+            Ok(handle) => Ok(Process {
+                handle: handle,
+                forget: false,
+                exit_code: None,
+                exit_signal: None,
+                deadline: 0,
+                stdin: our_stdin,
+                stdout: our_stdout,
+                stderr: our_stderr,
             })
-        }).map_err(IoError::from_rtio_error)
+        }
     }
 
     /// Executes the command as a child process, waiting for it to finish and
@@ -415,6 +393,58 @@ impl fmt::Show for Command {
     }
 }
 
+fn setup_io(io: StdioContainer) -> IoResult<(Option<PipeStream>, Option<PipeStream>)> {
+    let ours;
+    let theirs;
+    match io {
+        Ignored => {
+            theirs = None;
+            ours = None;
+        }
+        InheritFd(fd) => {
+            theirs = Some(PipeStream::from_filedesc(FileDesc::new(fd, false)));
+            ours = None;
+        }
+        CreatePipe(readable, _writable) => {
+            let PipePair { reader, writer } = try!(PipeStream::pair());
+            if readable {
+                theirs = Some(reader);
+                ours = Some(writer);
+            } else {
+                theirs = Some(writer);
+                ours = Some(reader);
+            }
+        }
+    }
+    Ok((theirs, ours))
+}
+
+// Allow the sys module to get access to the Command state
+impl sys::process::ProcessConfig<EnvKey, CString> for Command {
+    fn program(&self) -> &CString {
+        &self.program
+    }
+    fn args(&self) -> &[CString] {
+        self.args.as_slice()
+    }
+    fn env(&self) -> Option<&EnvMap> {
+        self.env.as_ref()
+    }
+    fn cwd(&self) -> Option<&CString> {
+        self.cwd.as_ref()
+    }
+    fn uid(&self) -> Option<uint> {
+        self.uid.clone()
+    }
+    fn gid(&self) -> Option<uint> {
+        self.gid.clone()
+    }
+    fn detach(&self) -> bool {
+        self.detach
+    }
+
+}
+
 /// The output of a finished process.
 #[deriving(PartialEq, Eq, Clone)]
 pub struct ProcessOutput {
@@ -494,9 +524,7 @@ impl Process {
     /// be successfully delivered if the child has exited, but not yet been
     /// reaped.
     pub fn kill(id: libc::pid_t, signal: int) -> IoResult<()> {
-        LocalIo::maybe_raise(|io| {
-            io.kill(id, signal)
-        }).map_err(IoError::from_rtio_error)
+        unsafe { ProcessImp::killpid(id, signal) }
     }
 
     /// Returns the process id of this child process
@@ -518,7 +546,42 @@ impl Process {
     ///
     /// If the signal delivery fails, the corresponding error is returned.
     pub fn signal(&mut self, signal: int) -> IoResult<()> {
-        self.handle.kill(signal).map_err(IoError::from_rtio_error)
+        #[cfg(unix)] fn collect_status(p: &mut Process) {
+            // On Linux (and possibly other unices), a process that has exited will
+            // continue to accept signals because it is "defunct". The delivery of
+            // signals will only fail once the child has been reaped. For this
+            // reason, if the process hasn't exited yet, then we attempt to collect
+            // their status with WNOHANG.
+            if p.exit_code.is_none() {
+                match p.handle.try_wait() {
+                    Some(code) => { p.exit_code = Some(code); }
+                    None => {}
+                }
+            }
+        }
+        #[cfg(windows)] fn collect_status(_p: &mut Process) {}
+
+        collect_status(self);
+
+        // if the process has finished, and therefore had waitpid called,
+        // and we kill it, then on unix we might ending up killing a
+        // newer process that happens to have the same (re-used) id
+        if self.exit_code.is_some() {
+            return Err(IoError {
+                kind: io::InvalidInput,
+                desc: "invalid argument: can't kill an exited process",
+                detail: None,
+            })
+        }
+
+        // A successfully delivered signal that isn't 0 (just a poll for being
+        // alive) is recorded for windows (see wait())
+        match unsafe { self.handle.kill(signal) } {
+            Ok(()) if signal == 0 => Ok(()),
+            Ok(()) => { self.exit_signal = Some(signal); Ok(()) }
+            Err(e) => Err(e),
+        }
+
     }
 
     /// Sends a signal to this child requesting that it exits. This is
@@ -545,10 +608,21 @@ impl Process {
     /// `set_timeout` and the timeout expires before the child exits.
     pub fn wait(&mut self) -> IoResult<ProcessExit> {
         drop(self.stdin.take());
-        match self.handle.wait() {
-            Ok(rtio::ExitSignal(s)) => Ok(ExitSignal(s)),
-            Ok(rtio::ExitStatus(s)) => Ok(ExitStatus(s)),
-            Err(e) => Err(IoError::from_rtio_error(e)),
+        match self.exit_code {
+            Some(code) => Ok(code),
+            None => {
+                let code = try!(self.handle.wait(self.deadline));
+                // On windows, waitpid will never return a signal. If a signal
+                // was successfully delivered to the process, however, we can
+                // consider it as having died via a signal.
+                let code = match self.exit_signal {
+                    None => code,
+                    Some(signal) if cfg!(windows) => ExitSignal(signal),
+                    Some(..) => code,
+                };
+                self.exit_code = Some(code);
+                Ok(code)
+            }
         }
     }
 
@@ -594,7 +668,7 @@ impl Process {
     /// ```
     #[experimental = "the type of the timeout is likely to change"]
     pub fn set_timeout(&mut self, timeout_ms: Option<u64>) {
-        self.handle.set_timeout(timeout_ms)
+        self.deadline = timeout_ms.map(|i| i + sys::timer::now()).unwrap_or(0);
     }
 
     /// Simultaneously wait for the child to exit and collect all remaining
@@ -653,7 +727,6 @@ impl Drop for Process {
         drop(self.stdin.take());
         drop(self.stdout.take());
         drop(self.stderr.take());
-        drop(mem::replace(&mut self.extra_io, Vec::new()));
 
         self.set_timeout(None);
         let _ = self.wait().unwrap();
@@ -1109,8 +1182,7 @@ mod tests {
 
     #[test]
     fn dont_close_fd_on_command_spawn() {
-        use std::rt::rtio::{Truncate, Write};
-        use self::native::io::file;
+        use sys::fs;
 
         let path = if cfg!(windows) {
             Path::new("NUL")
@@ -1118,7 +1190,7 @@ mod tests {
             Path::new("/dev/null")
         };
 
-        let mut fdes = match file::open(&path.to_c_str(), Truncate, Write) {
+        let mut fdes = match fs::open(&path, Truncate, Write) {
             Ok(f) => f,
             Err(_) => panic!("failed to open file descriptor"),
         };
@@ -1126,7 +1198,7 @@ mod tests {
         let mut cmd = pwd_cmd();
         let _ = cmd.stdout(InheritFd(fdes.fd()));
         assert!(cmd.status().unwrap().success());
-        assert!(fdes.inner_write("extra write\n".as_bytes()).is_ok());
+        assert!(fdes.write("extra write\n".as_bytes()).is_ok());
     }
 
     #[test]
diff --git a/src/libstd/sys/common/helper_thread.rs b/src/libstd/sys/common/helper_thread.rs
index 8c8ec4466a7..87907fde277 100644
--- a/src/libstd/sys/common/helper_thread.rs
+++ b/src/libstd/sys/common/helper_thread.rs
@@ -20,8 +20,6 @@
 //! can be created in the future and there must be no active timers at that
 //! time.
 
-#![macro_escape]
-
 use mem;
 use rt::bookkeeping;
 use rt::mutex::StaticNativeMutex;
@@ -57,15 +55,6 @@ pub struct Helper<M> {
     pub initialized: UnsafeCell<bool>,
 }
 
-macro_rules! helper_init( (static $name:ident: Helper<$m:ty>) => (
-    static $name: Helper<$m> = Helper {
-        lock: ::std::rt::mutex::NATIVE_MUTEX_INIT,
-        chan: ::std::cell::UnsafeCell { value: 0 as *mut Sender<$m> },
-        signal: ::std::cell::UnsafeCell { value: 0 },
-        initialized: ::std::cell::UnsafeCell { value: false },
-    };
-) )
-
 impl<M: Send> Helper<M> {
     /// Lazily boots a helper thread, becoming a no-op if the helper has already
     /// been spawned.
diff --git a/src/libstd/platform_imp/unix/fs.rs b/src/libstd/sys/unix/fs.rs
index 3dcd99859e8..3dcd99859e8 100644
--- a/src/libstd/platform_imp/unix/fs.rs
+++ b/src/libstd/sys/unix/fs.rs
diff --git a/src/libstd/sys/unix/mod.rs b/src/libstd/sys/unix/mod.rs
index 6295864e0e1..b404dc7fdbd 100644
--- a/src/libstd/sys/unix/mod.rs
+++ b/src/libstd/sys/unix/mod.rs
@@ -17,7 +17,6 @@ use prelude::*;
 use io::{mod, IoResult, IoError};
 use sys_common::mkerr_libc;
 
-
 macro_rules! helper_init( (static $name:ident: Helper<$m:ty>) => (
     static $name: Helper<$m> = Helper {
         lock: ::rt::mutex::NATIVE_MUTEX_INIT,
@@ -34,6 +33,7 @@ pub mod tcp;
 pub mod udp;
 pub mod pipe;
 pub mod helper_signal;
+pub mod process;
 
 pub mod addrinfo {
     pub use sys_common::net::get_host_addresses;
diff --git a/src/libstd/sys/unix/process.rs b/src/libstd/sys/unix/process.rs
new file mode 100644
index 00000000000..0965d98d9b0
--- /dev/null
+++ b/src/libstd/sys/unix/process.rs
@@ -0,0 +1,587 @@
+// 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 libc::{mod, pid_t, c_void, c_int};
+use c_str::CString;
+use io::{mod, IoResult, IoError};
+use mem;
+use os;
+use ptr;
+use prelude::*;
+use io::process::{ProcessExit, ExitStatus, ExitSignal};
+use collections;
+use path::BytesContainer;
+use hash::Hash;
+
+use sys::{mod, retry, c, wouldblock, set_nonblocking, ms_to_timeval};
+use sys::fs::FileDesc;
+use sys_common::helper_thread::Helper;
+use sys_common::{AsFileDesc, mkerr_libc, timeout};
+
+pub use sys_common::ProcessConfig;
+
+helper_init!(static HELPER: Helper<Req>)
+
+/// The unique id of the process (this should never be negative).
+pub struct Process {
+    pub pid: pid_t
+}
+
+enum Req {
+    NewChild(libc::pid_t, Sender<ProcessExit>, u64),
+}
+
+impl Process {
+    pub fn id(&self) -> pid_t {
+        self.pid
+    }
+
+    pub unsafe fn kill(&self, signal: int) -> IoResult<()> {
+        Process::killpid(self.pid, signal)
+    }
+
+    pub unsafe fn killpid(pid: pid_t, signal: int) -> IoResult<()> {
+        let r = libc::funcs::posix88::signal::kill(pid, signal as c_int);
+        mkerr_libc(r)
+    }
+
+    pub fn spawn<K, V, C, P>(cfg: &C, in_fd: Option<P>,
+                              out_fd: Option<P>, err_fd: Option<P>)
+                              -> IoResult<Process>
+        where C: ProcessConfig<K, V>, P: AsFileDesc,
+              K: BytesContainer + Eq + Hash, V: BytesContainer
+    {
+        use libc::funcs::posix88::unistd::{fork, dup2, close, chdir, execvp};
+        use libc::funcs::bsd44::getdtablesize;
+
+        mod rustrt {
+            extern {
+                pub fn rust_unset_sigprocmask();
+            }
+        }
+
+        #[cfg(target_os = "macos")]
+        unsafe fn set_environ(envp: *const c_void) {
+            extern { fn _NSGetEnviron() -> *mut *const c_void; }
+
+            *_NSGetEnviron() = envp;
+        }
+        #[cfg(not(target_os = "macos"))]
+        unsafe fn set_environ(envp: *const c_void) {
+            extern { static mut environ: *const c_void; }
+            environ = envp;
+        }
+
+        unsafe fn set_cloexec(fd: c_int) {
+            let ret = c::ioctl(fd, c::FIOCLEX);
+            assert_eq!(ret, 0);
+        }
+
+        let dirp = cfg.cwd().map(|c| c.as_ptr()).unwrap_or(ptr::null());
+
+        // temporary until unboxed closures land
+        let cfg = unsafe {
+            mem::transmute::<&ProcessConfig<K,V>,&'static ProcessConfig<K,V>>(cfg)
+        };
+
+        with_envp(cfg.env(), proc(envp) {
+            with_argv(cfg.program(), cfg.args(), proc(argv) unsafe {
+                let (input, mut output) = try!(sys::os::pipe());
+
+                // We may use this in the child, so perform allocations before the
+                // fork
+                let devnull = "/dev/null".to_c_str();
+
+                set_cloexec(output.fd());
+
+                let pid = fork();
+                if pid < 0 {
+                    return Err(super::last_error())
+                } else if pid > 0 {
+                    drop(output);
+                    let mut bytes = [0, ..4];
+                    return match input.read(bytes) {
+                        Ok(4) => {
+                            let errno = (bytes[0] as i32 << 24) |
+                                        (bytes[1] as i32 << 16) |
+                                        (bytes[2] as i32 <<  8) |
+                                        (bytes[3] as i32 <<  0);
+                            Err(super::decode_error(errno))
+                        }
+                        Err(..) => Ok(Process { pid: pid }),
+                        Ok(..) => panic!("short read on the cloexec pipe"),
+                    };
+                }
+
+                // And at this point we've reached a special time in the life of the
+                // child. The child must now be considered hamstrung and unable to
+                // do anything other than syscalls really. Consider the following
+                // scenario:
+                //
+                //      1. Thread A of process 1 grabs the malloc() mutex
+                //      2. Thread B of process 1 forks(), creating thread C
+                //      3. Thread C of process 2 then attempts to malloc()
+                //      4. The memory of process 2 is the same as the memory of
+                //         process 1, so the mutex is locked.
+                //
+                // This situation looks a lot like deadlock, right? It turns out
+                // that this is what pthread_atfork() takes care of, which is
+                // presumably implemented across platforms. The first thing that
+                // threads to *before* forking is to do things like grab the malloc
+                // mutex, and then after the fork they unlock it.
+                //
+                // Despite this information, libnative's spawn has been witnessed to
+                // deadlock on both OSX and FreeBSD. I'm not entirely sure why, but
+                // all collected backtraces point at malloc/free traffic in the
+                // child spawned process.
+                //
+                // For this reason, the block of code below should contain 0
+                // invocations of either malloc of free (or their related friends).
+                //
+                // As an example of not having malloc/free traffic, we don't close
+                // this file descriptor by dropping the FileDesc (which contains an
+                // allocation). Instead we just close it manually. This will never
+                // have the drop glue anyway because this code never returns (the
+                // child will either exec() or invoke libc::exit)
+                let _ = libc::close(input.fd());
+
+                fn fail(output: &mut FileDesc) -> ! {
+                    let errno = sys::os::errno();
+                    let bytes = [
+                        (errno >> 24) as u8,
+                        (errno >> 16) as u8,
+                        (errno >>  8) as u8,
+                        (errno >>  0) as u8,
+                    ];
+                    assert!(output.write(bytes).is_ok());
+                    unsafe { libc::_exit(1) }
+                }
+
+                rustrt::rust_unset_sigprocmask();
+
+                // If a stdio file descriptor is set to be ignored (via a -1 file
+                // descriptor), then we don't actually close it, but rather open
+                // up /dev/null into that file descriptor. Otherwise, the first file
+                // descriptor opened up in the child would be numbered as one of the
+                // stdio file descriptors, which is likely to wreak havoc.
+                let setup = |src: Option<P>, dst: c_int| {
+                    let src = match src {
+                        None => {
+                            let flags = if dst == libc::STDIN_FILENO {
+                                libc::O_RDONLY
+                            } else {
+                                libc::O_RDWR
+                            };
+                            libc::open(devnull.as_ptr(), flags, 0)
+                        }
+                        Some(obj) => {
+                            let fd = obj.as_fd().fd();
+                            // Leak the memory and the file descriptor. We're in the
+                            // child now an all our resources are going to be
+                            // cleaned up very soon
+                            mem::forget(obj);
+                            fd
+                        }
+                    };
+                    src != -1 && retry(|| dup2(src, dst)) != -1
+                };
+
+                if !setup(in_fd, libc::STDIN_FILENO) { fail(&mut output) }
+                if !setup(out_fd, libc::STDOUT_FILENO) { fail(&mut output) }
+                if !setup(err_fd, libc::STDERR_FILENO) { fail(&mut output) }
+
+                // close all other fds
+                for fd in range(3, getdtablesize()).rev() {
+                    if fd != output.fd() {
+                        let _ = close(fd as c_int);
+                    }
+                }
+
+                match cfg.gid() {
+                    Some(u) => {
+                        if libc::setgid(u as libc::gid_t) != 0 {
+                            fail(&mut output);
+                        }
+                    }
+                    None => {}
+                }
+                match cfg.uid() {
+                    Some(u) => {
+                        // When dropping privileges from root, the `setgroups` call
+                        // will remove any extraneous groups. If we don't call this,
+                        // then even though our uid has dropped, we may still have
+                        // groups that enable us to do super-user things. This will
+                        // fail if we aren't root, so don't bother checking the
+                        // return value, this is just done as an optimistic
+                        // privilege dropping function.
+                        extern {
+                            fn setgroups(ngroups: libc::c_int,
+                                         ptr: *const libc::c_void) -> libc::c_int;
+                        }
+                        let _ = setgroups(0, 0 as *const libc::c_void);
+
+                        if libc::setuid(u as libc::uid_t) != 0 {
+                            fail(&mut output);
+                        }
+                    }
+                    None => {}
+                }
+                if cfg.detach() {
+                    // Don't check the error of setsid because it fails if we're the
+                    // process leader already. We just forked so it shouldn't return
+                    // error, but ignore it anyway.
+                    let _ = libc::setsid();
+                }
+                if !dirp.is_null() && chdir(dirp) == -1 {
+                    fail(&mut output);
+                }
+                if !envp.is_null() {
+                    set_environ(envp);
+                }
+                let _ = execvp(*argv, argv as *mut _);
+                fail(&mut output);
+            })
+        })
+    }
+
+    pub fn wait(&self, deadline: u64) -> IoResult<ProcessExit> {
+        use std::cmp;
+        use std::comm;
+
+        static mut WRITE_FD: libc::c_int = 0;
+
+        let mut status = 0 as c_int;
+        if deadline == 0 {
+            return match retry(|| unsafe { c::waitpid(self.pid, &mut status, 0) }) {
+                -1 => panic!("unknown waitpid error: {}", super::last_error()),
+                _ => Ok(translate_status(status)),
+            }
+        }
+
+        // On unix, wait() and its friends have no timeout parameters, so there is
+        // no way to time out a thread in wait(). From some googling and some
+        // thinking, it appears that there are a few ways to handle timeouts in
+        // wait(), but the only real reasonable one for a multi-threaded program is
+        // to listen for SIGCHLD.
+        //
+        // With this in mind, the waiting mechanism with a timeout barely uses
+        // waitpid() at all. There are a few times that waitpid() is invoked with
+        // WNOHANG, but otherwise all the necessary blocking is done by waiting for
+        // a SIGCHLD to arrive (and that blocking has a timeout). Note, however,
+        // that waitpid() is still used to actually reap the child.
+        //
+        // Signal handling is super tricky in general, and this is no exception. Due
+        // to the async nature of SIGCHLD, we use the self-pipe trick to transmit
+        // data out of the signal handler to the rest of the application. The first
+        // idea would be to have each thread waiting with a timeout to read this
+        // output file descriptor, but a write() is akin to a signal(), not a
+        // broadcast(), so it would only wake up one thread, and possibly the wrong
+        // thread. Hence a helper thread is used.
+        //
+        // The helper thread here is responsible for farming requests for a
+        // waitpid() with a timeout, and then processing all of the wait requests.
+        // By guaranteeing that only this helper thread is reading half of the
+        // self-pipe, we're sure that we'll never lose a SIGCHLD. This helper thread
+        // is also responsible for select() to wait for incoming messages or
+        // incoming SIGCHLD messages, along with passing an appropriate timeout to
+        // select() to wake things up as necessary.
+        //
+        // The ordering of the following statements is also very purposeful. First,
+        // we must be guaranteed that the helper thread is booted and available to
+        // receive SIGCHLD signals, and then we must also ensure that we do a
+        // nonblocking waitpid() at least once before we go ask the sigchld helper.
+        // This prevents the race where the child exits, we boot the helper, and
+        // then we ask for the child's exit status (never seeing a sigchld).
+        //
+        // The actual communication between the helper thread and this thread is
+        // quite simple, just a channel moving data around.
+
+        unsafe { HELPER.boot(register_sigchld, waitpid_helper) }
+
+        match self.try_wait() {
+            Some(ret) => return Ok(ret),
+            None => {}
+        }
+
+        let (tx, rx) = channel();
+        unsafe { HELPER.send(NewChild(self.pid, tx, deadline)); }
+        return match rx.recv_opt() {
+            Ok(e) => Ok(e),
+            Err(()) => Err(timeout("wait timed out")),
+        };
+
+        // Register a new SIGCHLD handler, returning the reading half of the
+        // self-pipe plus the old handler registered (return value of sigaction).
+        //
+        // Be sure to set up the self-pipe first because as soon as we register a
+        // handler we're going to start receiving signals.
+        fn register_sigchld() -> (libc::c_int, c::sigaction) {
+            unsafe {
+                let mut pipes = [0, ..2];
+                assert_eq!(libc::pipe(pipes.as_mut_ptr()), 0);
+                set_nonblocking(pipes[0], true).ok().unwrap();
+                set_nonblocking(pipes[1], true).ok().unwrap();
+                WRITE_FD = pipes[1];
+
+                let mut old: c::sigaction = mem::zeroed();
+                let mut new: c::sigaction = mem::zeroed();
+                new.sa_handler = sigchld_handler;
+                new.sa_flags = c::SA_NOCLDSTOP;
+                assert_eq!(c::sigaction(c::SIGCHLD, &new, &mut old), 0);
+                (pipes[0], old)
+            }
+        }
+
+        // Helper thread for processing SIGCHLD messages
+        fn waitpid_helper(input: libc::c_int,
+                          messages: Receiver<Req>,
+                          (read_fd, old): (libc::c_int, c::sigaction)) {
+            set_nonblocking(input, true).ok().unwrap();
+            let mut set: c::fd_set = unsafe { mem::zeroed() };
+            let mut tv: libc::timeval;
+            let mut active = Vec::<(libc::pid_t, Sender<ProcessExit>, u64)>::new();
+            let max = cmp::max(input, read_fd) + 1;
+
+            'outer: loop {
+                // Figure out the timeout of our syscall-to-happen. If we're waiting
+                // for some processes, then they'll have a timeout, otherwise we
+                // wait indefinitely for a message to arrive.
+                //
+                // FIXME: sure would be nice to not have to scan the entire array
+                let min = active.iter().map(|a| *a.ref2()).enumerate().min_by(|p| {
+                    p.val1()
+                });
+                let (p, idx) = match min {
+                    Some((idx, deadline)) => {
+                        let now = sys::timer::now();
+                        let ms = if now < deadline {deadline - now} else {0};
+                        tv = ms_to_timeval(ms);
+                        (&mut tv as *mut _, idx)
+                    }
+                    None => (ptr::null_mut(), -1),
+                };
+
+                // Wait for something to happen
+                c::fd_set(&mut set, input);
+                c::fd_set(&mut set, read_fd);
+                match unsafe { c::select(max, &mut set, ptr::null_mut(),
+                                         ptr::null_mut(), p) } {
+                    // interrupted, retry
+                    -1 if os::errno() == libc::EINTR as uint => continue,
+
+                    // We read something, break out and process
+                    1 | 2 => {}
+
+                    // Timeout, the pending request is removed
+                    0 => {
+                        drop(active.remove(idx));
+                        continue
+                    }
+
+                    n => panic!("error in select {} ({})", os::errno(), n),
+                }
+
+                // Process any pending messages
+                if drain(input) {
+                    loop {
+                        match messages.try_recv() {
+                            Ok(NewChild(pid, tx, deadline)) => {
+                                active.push((pid, tx, deadline));
+                            }
+                            Err(comm::Disconnected) => {
+                                assert!(active.len() == 0);
+                                break 'outer;
+                            }
+                            Err(comm::Empty) => break,
+                        }
+                    }
+                }
+
+                // If a child exited (somehow received SIGCHLD), then poll all
+                // children to see if any of them exited.
+                //
+                // We also attempt to be responsible netizens when dealing with
+                // SIGCHLD by invoking any previous SIGCHLD handler instead of just
+                // ignoring any previous SIGCHLD handler. Note that we don't provide
+                // a 1:1 mapping of our handler invocations to the previous handler
+                // invocations because we drain the `read_fd` entirely. This is
+                // probably OK because the kernel is already allowed to coalesce
+                // simultaneous signals, we're just doing some extra coalescing.
+                //
+                // Another point of note is that this likely runs the signal handler
+                // on a different thread than the one that received the signal. I
+                // *think* this is ok at this time.
+                //
+                // The main reason for doing this is to allow stdtest to run native
+                // tests as well. Both libgreen and libnative are running around
+                // with process timeouts, but libgreen should get there first
+                // (currently libuv doesn't handle old signal handlers).
+                if drain(read_fd) {
+                    let i: uint = unsafe { mem::transmute(old.sa_handler) };
+                    if i != 0 {
+                        assert!(old.sa_flags & c::SA_SIGINFO == 0);
+                        (old.sa_handler)(c::SIGCHLD);
+                    }
+
+                    // FIXME: sure would be nice to not have to scan the entire
+                    //        array...
+                    active.retain(|&(pid, ref tx, _)| {
+                        let pr = Process { pid: pid };
+                        match pr.try_wait() {
+                            Some(msg) => { tx.send(msg); false }
+                            None => true,
+                        }
+                    });
+                }
+            }
+
+            // Once this helper thread is done, we re-register the old sigchld
+            // handler and close our intermediate file descriptors.
+            unsafe {
+                assert_eq!(c::sigaction(c::SIGCHLD, &old, ptr::null_mut()), 0);
+                let _ = libc::close(read_fd);
+                let _ = libc::close(WRITE_FD);
+                WRITE_FD = -1;
+            }
+        }
+
+        // Drain all pending data from the file descriptor, returning if any data
+        // could be drained. This requires that the file descriptor is in
+        // nonblocking mode.
+        fn drain(fd: libc::c_int) -> bool {
+            let mut ret = false;
+            loop {
+                let mut buf = [0u8, ..1];
+                match unsafe {
+                    libc::read(fd, buf.as_mut_ptr() as *mut libc::c_void,
+                               buf.len() as libc::size_t)
+                } {
+                    n if n > 0 => { ret = true; }
+                    0 => return true,
+                    -1 if wouldblock() => return ret,
+                    n => panic!("bad read {} ({})", os::last_os_error(), n),
+                }
+            }
+        }
+
+        // Signal handler for SIGCHLD signals, must be async-signal-safe!
+        //
+        // This function will write to the writing half of the "self pipe" to wake
+        // up the helper thread if it's waiting. Note that this write must be
+        // nonblocking because if it blocks and the reader is the thread we
+        // interrupted, then we'll deadlock.
+        //
+        // When writing, if the write returns EWOULDBLOCK then we choose to ignore
+        // it. At that point we're guaranteed that there's something in the pipe
+        // which will wake up the other end at some point, so we just allow this
+        // signal to be coalesced with the pending signals on the pipe.
+        extern fn sigchld_handler(_signum: libc::c_int) {
+            let msg = 1i;
+            match unsafe {
+                libc::write(WRITE_FD, &msg as *const _ as *const libc::c_void, 1)
+            } {
+                1 => {}
+                -1 if wouldblock() => {} // see above comments
+                n => panic!("bad error on write fd: {} {}", n, os::errno()),
+            }
+        }
+    }
+
+    pub fn try_wait(&self) -> Option<ProcessExit> {
+        let mut status = 0 as c_int;
+        match retry(|| unsafe {
+            c::waitpid(self.pid, &mut status, c::WNOHANG)
+        }) {
+            n if n == self.pid => Some(translate_status(status)),
+            0 => None,
+            n => panic!("unknown waitpid error `{}`: {}", n,
+                       super::last_error()),
+        }
+    }
+}
+
+fn with_argv<T>(prog: &CString, args: &[CString],
+                cb: proc(*const *const libc::c_char) -> T) -> 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
+    // lifetime of the various CStrings involved is guaranteed to be
+    // larger than the lifetime of our invocation of cb, but this is
+    // technically unsafe as the callback could leak these pointers
+    // out of our scope.
+    ptrs.push(prog.as_ptr());
+    ptrs.extend(args.iter().map(|tmp| tmp.as_ptr()));
+
+    // Add a terminating null pointer (required by libc).
+    ptrs.push(ptr::null());
+
+    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
+{
+    // 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
+    // these strings locally, yet expose a raw pointer to them, we
+    // create a temporary vector to own the CStrings that outlives the
+    // call to cb.
+    match env {
+        Some(env) => {
+            let mut tmps = Vec::with_capacity(env.len());
+
+            for pair in env.iter() {
+                let mut kv = Vec::new();
+                kv.push_all(pair.ref0().container_as_bytes());
+                kv.push('=' as u8);
+                kv.push_all(pair.ref1().container_as_bytes());
+                kv.push(0); // terminating null
+                tmps.push(kv);
+            }
+
+            // As with `with_argv`, this is unsafe, since cb could leak the pointers.
+            let mut ptrs: Vec<*const libc::c_char> =
+                tmps.iter()
+                    .map(|tmp| tmp.as_ptr() as *const libc::c_char)
+                    .collect();
+            ptrs.push(ptr::null());
+
+            cb(ptrs.as_ptr() as *const c_void)
+        }
+        _ => cb(ptr::null())
+    }
+}
+
+fn translate_status(status: c_int) -> ProcessExit {
+    #![allow(non_snake_case)]
+    #[cfg(any(target_os = "linux", target_os = "android"))]
+    mod imp {
+        pub fn WIFEXITED(status: i32) -> bool { (status & 0xff) == 0 }
+        pub fn WEXITSTATUS(status: i32) -> i32 { (status >> 8) & 0xff }
+        pub fn WTERMSIG(status: i32) -> i32 { status & 0x7f }
+    }
+
+    #[cfg(any(target_os = "macos",
+              target_os = "ios",
+              target_os = "freebsd",
+              target_os = "dragonfly"))]
+    mod imp {
+        pub fn WIFEXITED(status: i32) -> bool { (status & 0x7f) == 0 }
+        pub fn WEXITSTATUS(status: i32) -> i32 { status >> 8 }
+        pub fn WTERMSIG(status: i32) -> i32 { status & 0o177 }
+    }
+
+    if imp::WIFEXITED(status) {
+        ExitStatus(imp::WEXITSTATUS(status) as int)
+    } else {
+        ExitSignal(imp::WTERMSIG(status) as int)
+    }
+}
diff --git a/src/libstd/platform_imp/windows/fs.rs b/src/libstd/sys/windows/fs.rs
index a07688b2fed..a07688b2fed 100644
--- a/src/libstd/platform_imp/windows/fs.rs
+++ b/src/libstd/sys/windows/fs.rs
diff --git a/src/libstd/sys/windows/mod.rs b/src/libstd/sys/windows/mod.rs
index 6f6ca3f2e62..f50244701e4 100644
--- a/src/libstd/sys/windows/mod.rs
+++ b/src/libstd/sys/windows/mod.rs
@@ -40,6 +40,7 @@ pub mod tcp;
 pub mod udp;
 pub mod pipe;
 pub mod helper_signal;
+pub mod process;
 
 pub mod addrinfo {
     pub use sys_common::net::get_host_addresses;
diff --git a/src/libstd/sys/windows/process.rs b/src/libstd/sys/windows/process.rs
new file mode 100644
index 00000000000..67e87841ed2
--- /dev/null
+++ b/src/libstd/sys/windows/process.rs
@@ -0,0 +1,511 @@
+// Copyright 2012-2014 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 libc::{pid_t, c_void, c_int};
+use libc;
+use c_str::CString;
+use io;
+use mem;
+use os;
+use ptr;
+use prelude::*;
+use io::process::{ProcessExit, ExitStatus, ExitSignal};
+use collections;
+use path::BytesContainer;
+use hash::Hash;
+use io::{IoResult, IoError};
+
+use sys::fs;
+use sys::{mod, retry, c, wouldblock, set_nonblocking, ms_to_timeval, timer};
+use sys::fs::FileDesc;
+use sys_common::helper_thread::Helper;
+use sys_common::{AsFileDesc, mkerr_libc, timeout};
+
+use io::fs::PathExtensions;
+use string::String;
+
+pub use sys_common::ProcessConfig;
+
+/**
+ * A value representing a child process.
+ *
+ * The lifetime of this value is linked to the lifetime of the actual
+ * process - the Process destructor calls self.finish() which waits
+ * for the process to terminate.
+ */
+pub struct Process {
+    /// The unique id of the process (this should never be negative).
+    pid: pid_t,
+
+    /// A HANDLE to the process, which will prevent the pid being
+    /// re-used until the handle is closed.
+    handle: *mut (),
+}
+
+impl Drop for Process {
+    fn drop(&mut self) {
+        free_handle(self.handle);
+    }
+}
+
+impl Process {
+    pub fn id(&self) -> pid_t {
+        self.pid
+    }
+
+    pub unsafe fn kill(&self, signal: int) -> IoResult<()> {
+        Process::killpid(self.pid, signal)
+    }
+
+    pub unsafe fn killpid(pid: pid_t, signal: int) -> IoResult<()> {
+        let handle = libc::OpenProcess(libc::PROCESS_TERMINATE |
+                                       libc::PROCESS_QUERY_INFORMATION,
+                                       libc::FALSE, pid as libc::DWORD);
+        if handle.is_null() {
+            return Err(super::last_error())
+        }
+        let ret = match signal {
+            // test for existence on signal 0
+            0 => {
+                let mut status = 0;
+                let ret = libc::GetExitCodeProcess(handle, &mut status);
+                if ret == 0 {
+                    Err(super::last_error())
+                } else if status != libc::STILL_ACTIVE {
+                    Err(IoError {
+                        kind: io::InvalidInput,
+                        desc: "no process to kill",
+                        detail: None,
+                    })
+                } else {
+                    Ok(())
+                }
+            }
+            15 | 9 => { // sigterm or sigkill
+                let ret = libc::TerminateProcess(handle, 1);
+                super::mkerr_winbool(ret)
+            }
+            _ => Err(IoError {
+                kind: io::IoUnavailable,
+                desc: "unsupported signal on windows",
+                detail: None,
+            })
+        };
+        let _ = libc::CloseHandle(handle);
+        return ret;
+    }
+
+    pub fn spawn<K, V, C, P>(cfg: &C, in_fd: Option<P>,
+                              out_fd: Option<P>, err_fd: Option<P>)
+                              -> IoResult<Process>
+        where C: ProcessConfig<K, V>, P: AsFileDesc,
+              K: BytesContainer + Eq + Hash, V: BytesContainer
+    {
+        use libc::types::os::arch::extra::{DWORD, HANDLE, STARTUPINFO};
+        use libc::consts::os::extra::{
+            TRUE, FALSE,
+            STARTF_USESTDHANDLES,
+            INVALID_HANDLE_VALUE,
+            DUPLICATE_SAME_ACCESS
+        };
+        use libc::funcs::extra::kernel32::{
+            GetCurrentProcess,
+            DuplicateHandle,
+            CloseHandle,
+            CreateProcessW
+        };
+        use libc::funcs::extra::msvcrt::get_osfhandle;
+
+        use mem;
+        use iter::Iterator;
+        use str::StrPrelude;
+
+        if cfg.gid().is_some() || cfg.uid().is_some() {
+            return Err(IoError {
+                kind: io::IoUnavailable,
+                desc: "unsupported gid/uid requested on windows",
+                detail: None,
+            })
+        }
+
+        // To have the spawning semantics of unix/windows stay the same, we need to
+        // read the *child's* PATH if one is provided. See #15149 for more details.
+        let program = cfg.env().and_then(|env| {
+            for (key, v) in env.iter() {
+                if b"PATH" != key.container_as_bytes() { continue }
+
+                // Split the value and test each path to see if the
+                // program exists.
+                for path in os::split_paths(v.container_as_bytes()).into_iter() {
+                    let path = path.join(cfg.program().as_bytes_no_nul())
+                                   .with_extension(os::consts::EXE_EXTENSION);
+                    if path.exists() {
+                        return Some(path.to_c_str())
+                    }
+                }
+                break
+            }
+            None
+        });
+
+        unsafe {
+            let mut si = zeroed_startupinfo();
+            si.cb = mem::size_of::<STARTUPINFO>() as DWORD;
+            si.dwFlags = STARTF_USESTDHANDLES;
+
+            let cur_proc = GetCurrentProcess();
+
+            // Similarly to unix, we don't actually leave holes for the stdio file
+            // descriptors, but rather open up /dev/null equivalents. These
+            // equivalents are drawn from libuv's windows process spawning.
+            let set_fd = |fd: &Option<P>, slot: &mut HANDLE,
+                          is_stdin: bool| {
+                match *fd {
+                    None => {
+                        let access = if is_stdin {
+                            libc::FILE_GENERIC_READ
+                        } else {
+                            libc::FILE_GENERIC_WRITE | libc::FILE_READ_ATTRIBUTES
+                        };
+                        let size = mem::size_of::<libc::SECURITY_ATTRIBUTES>();
+                        let mut sa = libc::SECURITY_ATTRIBUTES {
+                            nLength: size as libc::DWORD,
+                            lpSecurityDescriptor: ptr::null_mut(),
+                            bInheritHandle: 1,
+                        };
+                        let mut filename: Vec<u16> = "NUL".utf16_units().collect();
+                        filename.push(0);
+                        *slot = libc::CreateFileW(filename.as_ptr(),
+                                                  access,
+                                                  libc::FILE_SHARE_READ |
+                                                      libc::FILE_SHARE_WRITE,
+                                                  &mut sa,
+                                                  libc::OPEN_EXISTING,
+                                                  0,
+                                                  ptr::null_mut());
+                        if *slot == INVALID_HANDLE_VALUE {
+                            return Err(super::last_error())
+                        }
+                    }
+                    Some(ref fd) => {
+                        let orig = get_osfhandle(fd.as_fd().fd()) as HANDLE;
+                        if orig == INVALID_HANDLE_VALUE {
+                            return Err(super::last_error())
+                        }
+                        if DuplicateHandle(cur_proc, orig, cur_proc, slot,
+                                           0, TRUE, DUPLICATE_SAME_ACCESS) == FALSE {
+                            return Err(super::last_error())
+                        }
+                    }
+                }
+                Ok(())
+            };
+
+            try!(set_fd(&in_fd, &mut si.hStdInput, true));
+            try!(set_fd(&out_fd, &mut si.hStdOutput, false));
+            try!(set_fd(&err_fd, &mut si.hStdError, false));
+
+            let cmd_str = make_command_line(program.as_ref().unwrap_or(cfg.program()),
+                                            cfg.args());
+            let mut pi = zeroed_process_information();
+            let mut create_err = None;
+
+            // stolen from the libuv code.
+            let mut flags = libc::CREATE_UNICODE_ENVIRONMENT;
+            if cfg.detach() {
+                flags |= libc::DETACHED_PROCESS | libc::CREATE_NEW_PROCESS_GROUP;
+            }
+
+            with_envp(cfg.env(), |envp| {
+                with_dirp(cfg.cwd(), |dirp| {
+                    let mut cmd_str: Vec<u16> = cmd_str.as_slice().utf16_units().collect();
+                    cmd_str.push(0);
+                    let created = CreateProcessW(ptr::null(),
+                                                 cmd_str.as_mut_ptr(),
+                                                 ptr::null_mut(),
+                                                 ptr::null_mut(),
+                                                 TRUE,
+                                                 flags, envp, dirp,
+                                                 &mut si, &mut pi);
+                    if created == FALSE {
+                        create_err = Some(super::last_error());
+                    }
+                })
+            });
+
+            assert!(CloseHandle(si.hStdInput) != 0);
+            assert!(CloseHandle(si.hStdOutput) != 0);
+            assert!(CloseHandle(si.hStdError) != 0);
+
+            match create_err {
+                Some(err) => return Err(err),
+                None => {}
+            }
+
+            // We close the thread handle because we don't care about keeping the
+            // thread id valid, and we aren't keeping the thread handle around to be
+            // able to close it later. We don't close the process handle however
+            // because std::we want the process id to stay valid at least until the
+            // calling code closes the process handle.
+            assert!(CloseHandle(pi.hThread) != 0);
+
+            Ok(Process {
+                pid: pi.dwProcessId as pid_t,
+                handle: pi.hProcess as *mut ()
+            })
+        }
+    }
+
+    /**
+     * Waits for a process to exit and returns the exit code, failing
+     * if there is no process with the specified id.
+     *
+     * Note that this is private to avoid race conditions on unix where if
+     * a user calls waitpid(some_process.get_id()) then some_process.finish()
+     * and some_process.destroy() and some_process.finalize() will then either
+     * operate on a none-existent process or, even worse, on a newer process
+     * with the same id.
+     */
+    pub fn wait(&self, deadline: u64) -> IoResult<ProcessExit> {
+        use libc::types::os::arch::extra::DWORD;
+        use libc::consts::os::extra::{
+            SYNCHRONIZE,
+            PROCESS_QUERY_INFORMATION,
+            FALSE,
+            STILL_ACTIVE,
+            INFINITE,
+            WAIT_TIMEOUT,
+            WAIT_OBJECT_0,
+        };
+        use libc::funcs::extra::kernel32::{
+            OpenProcess,
+            GetExitCodeProcess,
+            CloseHandle,
+            WaitForSingleObject,
+        };
+
+        unsafe {
+            let process = OpenProcess(SYNCHRONIZE | PROCESS_QUERY_INFORMATION,
+                                      FALSE,
+                                      self.pid as DWORD);
+            if process.is_null() {
+                return Err(super::last_error())
+            }
+
+            loop {
+                let mut status = 0;
+                if GetExitCodeProcess(process, &mut status) == FALSE {
+                    let err = Err(super::last_error());
+                    assert!(CloseHandle(process) != 0);
+                    return err;
+                }
+                if status != STILL_ACTIVE {
+                    assert!(CloseHandle(process) != 0);
+                    return Ok(ExitStatus(status as int));
+                }
+                let interval = if deadline == 0 {
+                    INFINITE
+                } else {
+                    let now = timer::now();
+                    if deadline < now {0} else {(deadline - now) as u32}
+                };
+                match WaitForSingleObject(process, interval) {
+                    WAIT_OBJECT_0 => {}
+                    WAIT_TIMEOUT => {
+                        assert!(CloseHandle(process) != 0);
+                        return Err(timeout("process wait timed out"))
+                    }
+                    _ => {
+                        let err = Err(super::last_error());
+                        assert!(CloseHandle(process) != 0);
+                        return err
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn zeroed_startupinfo() -> libc::types::os::arch::extra::STARTUPINFO {
+    libc::types::os::arch::extra::STARTUPINFO {
+        cb: 0,
+        lpReserved: ptr::null_mut(),
+        lpDesktop: ptr::null_mut(),
+        lpTitle: ptr::null_mut(),
+        dwX: 0,
+        dwY: 0,
+        dwXSize: 0,
+        dwYSize: 0,
+        dwXCountChars: 0,
+        dwYCountCharts: 0,
+        dwFillAttribute: 0,
+        dwFlags: 0,
+        wShowWindow: 0,
+        cbReserved2: 0,
+        lpReserved2: ptr::null_mut(),
+        hStdInput: libc::INVALID_HANDLE_VALUE,
+        hStdOutput: libc::INVALID_HANDLE_VALUE,
+        hStdError: libc::INVALID_HANDLE_VALUE,
+    }
+}
+
+fn zeroed_process_information() -> libc::types::os::arch::extra::PROCESS_INFORMATION {
+    libc::types::os::arch::extra::PROCESS_INFORMATION {
+        hProcess: ptr::null_mut(),
+        hThread: ptr::null_mut(),
+        dwProcessId: 0,
+        dwThreadId: 0
+    }
+}
+
+fn make_command_line(prog: &CString, args: &[CString]) -> String {
+    let mut cmd = String::new();
+    append_arg(&mut cmd, prog.as_str()
+                             .expect("expected program name to be utf-8 encoded"));
+    for arg in args.iter() {
+        cmd.push(' ');
+        append_arg(&mut cmd, arg.as_str()
+                                .expect("expected argument to be utf-8 encoded"));
+    }
+    return cmd;
+
+    fn append_arg(cmd: &mut String, arg: &str) {
+        // If an argument has 0 characters then we need to quote it to ensure
+        // that it actually gets passed through on the command line or otherwise
+        // it will be dropped entirely when parsed on the other end.
+        let quote = arg.chars().any(|c| c == ' ' || c == '\t') || arg.len() == 0;
+        if quote {
+            cmd.push('"');
+        }
+        let argvec: Vec<char> = arg.chars().collect();
+        for i in range(0u, argvec.len()) {
+            append_char_at(cmd, argvec.as_slice(), i);
+        }
+        if quote {
+            cmd.push('"');
+        }
+    }
+
+    fn append_char_at(cmd: &mut String, arg: &[char], i: uint) {
+        match arg[i] {
+            '"' => {
+                // Escape quotes.
+                cmd.push_str("\\\"");
+            }
+            '\\' => {
+                if backslash_run_ends_in_quote(arg, i) {
+                    // Double all backslashes that are in runs before quotes.
+                    cmd.push_str("\\\\");
+                } else {
+                    // Pass other backslashes through unescaped.
+                    cmd.push('\\');
+                }
+            }
+            c => {
+                cmd.push(c);
+            }
+        }
+    }
+
+    fn backslash_run_ends_in_quote(s: &[char], mut i: uint) -> bool {
+        while i < s.len() && s[i] == '\\' {
+            i += 1;
+        }
+        return i < s.len() && s[i] == '"';
+    }
+}
+
+fn with_envp<K, V, T>(env: Option<&collections::HashMap<K, V>>,
+                      cb: |*mut c_void| -> T) -> T
+    where K: BytesContainer + Eq + Hash, V: BytesContainer
+{
+    // On Windows we pass an "environment block" which is not a char**, but
+    // rather a concatenation of null-terminated k=v\0 sequences, with a final
+    // \0 to terminate.
+    match env {
+        Some(env) => {
+            let mut blk = Vec::new();
+
+            for pair in env.iter() {
+                let kv = format!("{}={}",
+                                 pair.ref0().container_as_str().unwrap(),
+                                 pair.ref1().container_as_str().unwrap());
+                blk.extend(kv.as_slice().utf16_units());
+                blk.push(0);
+            }
+
+            blk.push(0);
+
+            cb(blk.as_mut_ptr() as *mut c_void)
+        }
+        _ => cb(ptr::null_mut())
+    }
+}
+
+fn with_dirp<T>(d: Option<&CString>, cb: |*const u16| -> T) -> T {
+    match d {
+      Some(dir) => {
+          let dir_str = dir.as_str()
+                           .expect("expected workingdirectory to be utf-8 encoded");
+          let mut dir_str: Vec<u16> = dir_str.utf16_units().collect();
+          dir_str.push(0);
+          cb(dir_str.as_ptr())
+      },
+      None => cb(ptr::null())
+    }
+}
+
+fn free_handle(handle: *mut ()) {
+    assert!(unsafe {
+        libc::CloseHandle(mem::transmute(handle)) != 0
+    })
+}
+
+#[cfg(test)]
+mod tests {
+
+    #[test]
+    fn test_make_command_line() {
+        use prelude::*;
+        use str;
+        use c_str::CString;
+        use super::make_command_line;
+
+        fn test_wrapper(prog: &str, args: &[&str]) -> String {
+            make_command_line(&prog.to_c_str(),
+                              args.iter()
+                                  .map(|a| a.to_c_str())
+                                  .collect::<Vec<CString>>()
+                                  .as_slice())
+        }
+
+        assert_eq!(
+            test_wrapper("prog", ["aaa", "bbb", "ccc"]),
+            "prog aaa bbb ccc".to_string()
+        );
+
+        assert_eq!(
+            test_wrapper("C:\\Program Files\\blah\\blah.exe", ["aaa"]),
+            "\"C:\\Program Files\\blah\\blah.exe\" aaa".to_string()
+        );
+        assert_eq!(
+            test_wrapper("C:\\Program Files\\test", ["aa\"bb"]),
+            "\"C:\\Program Files\\test\" aa\\\"bb".to_string()
+        );
+        assert_eq!(
+            test_wrapper("echo", ["a b c"]),
+            "echo \"a b c\"".to_string()
+        );
+        assert_eq!(
+            test_wrapper("\u03c0\u042f\u97f3\u00e6\u221e", []),
+            "\u03c0\u042f\u97f3\u00e6\u221e".to_string()
+        );
+    }
+}