process.rs

// Copyright 2012-2013 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 std::io;
use libc::{pid_t, c_void, c_int};
use libc;
use std::os;
use std::ptr;
use std::rt::rtio;
use p = std::io::process;

use super::IoResult;
use super::file;

#[cfg(windows)] use std::mem;
#[cfg(windows)] use std::strbuf::StrBuf;
#[cfg(not(windows))] use super::retry;

/**
 * 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 - on unix this will always be NULL, but on
    /// windows it will be a HANDLE to the process, which will prevent the
    /// pid being re-used until the handle is closed.
    handle: *(),

    /// None until finish() is called.
    exit_code: Option<p::ProcessExit>,

    /// Manually delivered signal
    exit_signal: Option<int>,
}

impl Process {
    /// Creates a new process using native process-spawning abilities provided
    /// by the OS. Operations on this process will be blocking instead of using
    /// the runtime for sleeping just this current task.
    ///
    /// # Arguments
    ///
    /// * prog - the program to run
    /// * args - the arguments to pass to the program, not including the program
    ///          itself
    /// * env - an optional environment to specify for the child process. If
    ///         this value is `None`, then the child will inherit the parent's
    ///         environment
    /// * cwd - an optionally specified current working directory of the child,
    ///         defaulting to the parent's current working directory
    /// * stdin, stdout, stderr - These optionally specified file descriptors
    ///     dictate where the stdin/out/err of the child process will go. If
    ///     these are `None`, then this module will bind the input/output to an
    ///     os pipe instead. This process takes ownership of these file
    ///     descriptors, closing them upon destruction of the process.
    pub fn spawn(config: p::ProcessConfig)
        -> Result<(Process, Vec<Option<file::FileDesc>>), io::IoError>
    {
        // right now we only handle stdin/stdout/stderr.
        if config.extra_io.len() > 0 {
            return Err(super::unimpl());
        }

        fn get_io(io: p::StdioContainer, ret: &mut Vec<Option<file::FileDesc>>)
            -> (Option<os::Pipe>, c_int)
        {
            match io {
                p::Ignored => { ret.push(None); (None, -1) }
                p::InheritFd(fd) => { ret.push(None); (None, fd) }
                p::CreatePipe(readable, _writable) => {
                    let pipe = os::pipe();
                    let (theirs, ours) = if readable {
                        (pipe.input, pipe.out)
                    } else {
                        (pipe.out, pipe.input)
                    };
                    ret.push(Some(file::FileDesc::new(ours, true)));
                    (Some(pipe), theirs)
                }
            }
        }

        let mut ret_io = Vec::new();
        let (in_pipe, in_fd) = get_io(config.stdin, &mut ret_io);
        let (out_pipe, out_fd) = get_io(config.stdout, &mut ret_io);
        let (err_pipe, err_fd) = get_io(config.stderr, &mut ret_io);

        let env = config.env.map(|a| a.to_owned());
        let cwd = config.cwd.map(|a| Path::new(a));
        let res = spawn_process_os(config, env, cwd.as_ref(), in_fd, out_fd,
                                   err_fd);

        unsafe {
            for pipe in in_pipe.iter() { let _ = libc::close(pipe.input); }
            for pipe in out_pipe.iter() { let _ = libc::close(pipe.out); }
            for pipe in err_pipe.iter() { let _ = libc::close(pipe.out); }
        }

        match res {
            Ok(res) => {
                Ok((Process {
                        pid: res.pid,
                        handle: res.handle,
                        exit_code: None,
                        exit_signal: None,
                    },
                    ret_io))
            }
            Err(e) => Err(e)
        }
    }

    pub fn kill(pid: libc::pid_t, signum: int) -> IoResult<()> {
        unsafe { killpid(pid, signum) }
    }
}

impl rtio::RtioProcess for Process {
    fn id(&self) -> pid_t { self.pid }

    fn wait(&mut self) -> p::ProcessExit {
        match self.exit_code {
            Some(code) => code,
            None => {
                let code = waitpid(self.pid);
                // 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) => p::ExitSignal(signal),
                    Some(..) => code,
                };
                self.exit_code = Some(code);
                code
            }
        }
    }

    fn kill(&mut self, signum: int) -> Result<(), io::IoError> {
        // 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 self.exit_code.is_none() {
            match waitpid_nowait(self.pid) {
                Some(code) => { self.exit_code = Some(code); }
                None => {}
            }
        }

        // 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
        match self.exit_code {
            Some(..) => return Err(io::IoError {
                kind: io::OtherIoError,
                desc: "can't kill an exited process",
                detail: None,
            }),
            None => {}
        }

        // A successfully delivered signal that isn't 0 (just a poll for being
        // alive) is recorded for windows (see wait())
        match unsafe { killpid(self.pid, signum) } {
            Ok(()) if signum == 0 => Ok(()),
            Ok(()) => { self.exit_signal = Some(signum); Ok(()) }
            Err(e) => Err(e),
        }
    }
}

impl Drop for Process {
    fn drop(&mut self) {
        free_handle(self.handle);
    }
}

#[cfg(windows)]
unsafe fn killpid(pid: pid_t, signal: int) -> Result<(), io::IoError> {
    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(io::IoError {
                    kind: io::OtherIoError,
                    desc: "process no longer alive",
                    detail: None,
                })
            } else {
                Ok(())
            }
        }
        io::process::PleaseExitSignal | io::process::MustDieSignal => {
            let ret = libc::TerminateProcess(handle, 1);
            super::mkerr_winbool(ret)
        }
        _ => Err(io::IoError {
            kind: io::OtherIoError,
            desc: "unsupported signal on windows",
            detail: None,
        })
    };
    let _ = libc::CloseHandle(handle);
    return ret;
}

#[cfg(not(windows))]
unsafe fn killpid(pid: pid_t, signal: int) -> Result<(), io::IoError> {
    let r = libc::funcs::posix88::signal::kill(pid, signal as c_int);
    super::mkerr_libc(r)
}

struct SpawnProcessResult {
    pid: pid_t,
    handle: *(),
}

#[cfg(windows)]
fn spawn_process_os(config: p::ProcessConfig,
                    env: Option<~[(~str, ~str)]>,
                    dir: Option<&Path>,
                    in_fd: c_int, out_fd: c_int,
                    err_fd: c_int) -> IoResult<SpawnProcessResult> {
    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 std::mem;

    if config.gid.is_some() || config.uid.is_some() {
        return Err(io::IoError {
            kind: io::OtherIoError,
            desc: "unsupported gid/uid requested on windows",
            detail: None,
        })
    }

    unsafe {

        let mut si = zeroed_startupinfo();
        si.cb = mem::size_of::<STARTUPINFO>() as DWORD;
        si.dwFlags = STARTF_USESTDHANDLES;

        let cur_proc = GetCurrentProcess();

        if in_fd != -1 {
            let orig_std_in = get_osfhandle(in_fd) as HANDLE;
            if orig_std_in == INVALID_HANDLE_VALUE as HANDLE {
                fail!("failure in get_osfhandle: {}", os::last_os_error());
            }
            if DuplicateHandle(cur_proc, orig_std_in, cur_proc, &mut si.hStdInput,
                               0, TRUE, DUPLICATE_SAME_ACCESS) == FALSE {
                fail!("failure in DuplicateHandle: {}", os::last_os_error());
            }
        }

        if out_fd != -1 {
            let orig_std_out = get_osfhandle(out_fd) as HANDLE;
            if orig_std_out == INVALID_HANDLE_VALUE as HANDLE {
                fail!("failure in get_osfhandle: {}", os::last_os_error());
            }
            if DuplicateHandle(cur_proc, orig_std_out, cur_proc, &mut si.hStdOutput,
                               0, TRUE, DUPLICATE_SAME_ACCESS) == FALSE {
                fail!("failure in DuplicateHandle: {}", os::last_os_error());
            }
        }

        if err_fd != -1 {
            let orig_std_err = get_osfhandle(err_fd) as HANDLE;
            if orig_std_err == INVALID_HANDLE_VALUE as HANDLE {
                fail!("failure in get_osfhandle: {}", os::last_os_error());
            }
            if DuplicateHandle(cur_proc, orig_std_err, cur_proc, &mut si.hStdError,
                               0, TRUE, DUPLICATE_SAME_ACCESS) == FALSE {
                fail!("failure in DuplicateHandle: {}", os::last_os_error());
            }
        }

        let cmd = make_command_line(config.program, config.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 config.detach {
            flags |= libc::DETACHED_PROCESS | libc::CREATE_NEW_PROCESS_GROUP;
        }

        with_envp(env, |envp| {
            with_dirp(dir, |dirp| {
                os::win32::as_mut_utf16_p(cmd, |cmdp| {
                    let created = CreateProcessW(ptr::null(), cmdp,
                                                 ptr::mut_null(), ptr::mut_null(), TRUE,
                                                 flags, envp, dirp, &mut si,
                                                 &mut pi);
                    if created == FALSE {
                        create_err = Some(super::last_error());
                    }
                })
            })
        });

        if in_fd != -1 { assert!(CloseHandle(si.hStdInput) != 0); }
        if out_fd != -1 { assert!(CloseHandle(si.hStdOutput) != 0); }
        if err_fd != -1 { 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(SpawnProcessResult {
            pid: pi.dwProcessId as pid_t,
            handle: pi.hProcess as *()
        })
    }
}

#[cfg(windows)]
fn zeroed_startupinfo() -> libc::types::os::arch::extra::STARTUPINFO {
    libc::types::os::arch::extra::STARTUPINFO {
        cb: 0,
        lpReserved: ptr::mut_null(),
        lpDesktop: ptr::mut_null(),
        lpTitle: ptr::mut_null(),
        dwX: 0,
        dwY: 0,
        dwXSize: 0,
        dwYSize: 0,
        dwXCountChars: 0,
        dwYCountCharts: 0,
        dwFillAttribute: 0,
        dwFlags: 0,
        wShowWindow: 0,
        cbReserved2: 0,
        lpReserved2: ptr::mut_null(),
        hStdInput: ptr::mut_null(),
        hStdOutput: ptr::mut_null(),
        hStdError: ptr::mut_null()
    }
}

#[cfg(windows)]
fn zeroed_process_information() -> libc::types::os::arch::extra::PROCESS_INFORMATION {
    libc::types::os::arch::extra::PROCESS_INFORMATION {
        hProcess: ptr::mut_null(),
        hThread: ptr::mut_null(),
        dwProcessId: 0,
        dwThreadId: 0
    }
}

#[cfg(windows)]
fn make_command_line(prog: &str, args: &[~str]) -> ~str {
    let mut cmd = StrBuf::new();
    append_arg(&mut cmd, prog);
    for arg in args.iter() {
        cmd.push_char(' ');
        append_arg(&mut cmd, *arg);
    }
    return cmd.into_owned();

    fn append_arg(cmd: &mut StrBuf, arg: &str) {
        let quote = arg.chars().any(|c| c == ' ' || c == '\t');
        if quote {
            cmd.push_char('"');
        }
        let argvec: Vec<char> = arg.chars().collect();
        for i in range(0u, argvec.len()) {
            append_char_at(cmd, &argvec, i);
        }
        if quote {
            cmd.push_char('"');
        }
    }

    fn append_char_at(cmd: &mut StrBuf, arg: &Vec<char>, i: uint) {
        match *arg.get(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_char('\\');
                }
            }
            c => {
                cmd.push_char(c);
            }
        }
    }

    fn backslash_run_ends_in_quote(s: &Vec<char>, mut i: uint) -> bool {
        while i < s.len() && *s.get(i) == '\\' {
            i += 1;
        }
        return i < s.len() && *s.get(i) == '"';
    }
}

#[cfg(unix)]
fn spawn_process_os(config: p::ProcessConfig,
                    env: Option<~[(~str, ~str)]>,
                    dir: Option<&Path>,
                    in_fd: c_int, out_fd: c_int,
                    err_fd: c_int) -> IoResult<SpawnProcessResult> {
    use libc::funcs::posix88::unistd::{fork, dup2, close, chdir, execvp};
    use libc::funcs::bsd44::getdtablesize;
    use io::c;

    mod rustrt {
        extern {
            pub fn rust_unset_sigprocmask();
        }
    }

    #[cfg(target_os = "macos")]
    unsafe fn set_environ(envp: *c_void) {
        extern { fn _NSGetEnviron() -> *mut *c_void; }

        *_NSGetEnviron() = envp;
    }
    #[cfg(not(target_os = "macos"))]
    unsafe fn set_environ(envp: *c_void) {
        extern { static mut environ: *c_void; }
        environ = envp;
    }

    unsafe fn set_cloexec(fd: c_int) {
        let ret = c::ioctl(fd, c::FIOCLEX);
        assert_eq!(ret, 0);
    }

    let dirp = dir.map(|p| p.to_c_str());
    let dirp = dirp.as_ref().map(|c| c.with_ref(|p| p)).unwrap_or(ptr::null());

    with_envp(env, proc(envp) {
        with_argv(config.program, config.args, proc(argv) unsafe {
            let pipe = os::pipe();
            let mut input = file::FileDesc::new(pipe.input, true);
            let mut output = file::FileDesc::new(pipe.out, true);

            set_cloexec(output.fd());

            let pid = fork();
            if pid < 0 {
                fail!("failure in fork: {}", os::last_os_error());
            } else if pid > 0 {
                drop(output);
                let mut bytes = [0, ..4];
                return match input.inner_read(bytes) {
                    Ok(4) => {
                        let errno = (bytes[0] << 24) as i32 |
                                    (bytes[1] << 16) as i32 |
                                    (bytes[2] <<  8) as i32 |
                                    (bytes[3] <<  0) as i32;
                        Err(io::IoError::from_errno(errno as uint, false))
                    }
                    Err(e) => {
                        assert!(e.kind == io::BrokenPipe ||
                                e.kind == io::EndOfFile,
                                "unexpected error: {}", e);
                        Ok(SpawnProcessResult {
                            pid: pid,
                            handle: ptr::null()
                        })
                    }
                    Ok(..) => fail!("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 file::FileDesc) -> ! {
                let errno = os::errno();
                let bytes = [
                    (errno << 24) as u8,
                    (errno << 16) as u8,
                    (errno <<  8) as u8,
                    (errno <<  0) as u8,
                ];
                assert!(output.inner_write(bytes).is_ok());
                unsafe { libc::_exit(1) }
            }

            rustrt::rust_unset_sigprocmask();

            if in_fd == -1 {
                let _ = libc::close(libc::STDIN_FILENO);
            } else if retry(|| dup2(in_fd, 0)) == -1 {
                fail(&mut output);
            }
            if out_fd == -1 {
                let _ = libc::close(libc::STDOUT_FILENO);
            } else if retry(|| dup2(out_fd, 1)) == -1 {
                fail(&mut output);
            }
            if err_fd == -1 {
                let _ = libc::close(libc::STDERR_FILENO);
            } else if retry(|| dup2(err_fd, 2)) == -1 {
                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 config.gid {
                Some(u) => {
                    if libc::setgid(u as libc::gid_t) != 0 {
                        fail(&mut output);
                    }
                }
                None => {}
            }
            match config.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: *libc::c_void) -> libc::c_int;
                    }
                    let _ = setgroups(0, 0 as *libc::c_void);

                    if libc::setuid(u as libc::uid_t) != 0 {
                        fail(&mut output);
                    }
                }
                None => {}
            }
            if config.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);
            fail(&mut output);
        })
    })
}

#[cfg(unix)]
fn with_argv<T>(prog: &str, args: &[~str], cb: proc(**libc::c_char) -> T) -> T {
    // We can't directly convert `str`s into `*char`s, as someone needs to hold
    // a reference to the intermediary byte buffers. So first build an array to
    // hold all the ~[u8] byte strings.
    let mut tmps = Vec::with_capacity(args.len() + 1);

    tmps.push(prog.to_c_str());

    for arg in args.iter() {
        tmps.push(arg.to_c_str());
    }

    // Next, convert each of the byte strings into a pointer. This is
    // technically unsafe as the caller could leak these pointers out of our
    // scope.
    let mut ptrs: Vec<_> = tmps.iter().map(|tmp| tmp.with_ref(|buf| buf)).collect();

    // Finally, make sure we add a null pointer.
    ptrs.push(ptr::null());

    cb(ptrs.as_ptr())
}

#[cfg(unix)]
fn with_envp<T>(env: Option<~[(~str, ~str)]>, cb: proc(*c_void) -> T) -> T {
    // On posixy systems we can pass a char** for envp, which is a
    // null-terminated array of "k=v\n" strings. Like `with_argv`, we have to
    // have a temporary buffer to hold the intermediary `~[u8]` byte strings.
    match env {
        Some(env) => {
            let mut tmps = Vec::with_capacity(env.len());

            for pair in env.iter() {
                let kv = format!("{}={}", *pair.ref0(), *pair.ref1());
                tmps.push(kv.to_c_str());
            }

            // Once again, this is unsafe.
            let mut ptrs: Vec<*libc::c_char> = tmps.iter()
                                                   .map(|tmp| tmp.with_ref(|buf| buf))
                                                   .collect();
            ptrs.push(ptr::null());

            cb(ptrs.as_ptr() as *c_void)
        }
        _ => cb(ptr::null())
    }
}

#[cfg(windows)]
fn with_envp<T>(env: Option<~[(~str, ~str)]>, cb: |*mut c_void| -> T) -> T {
    // On win32 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(), *pair.ref1());
                blk.push_all(kv.to_utf16().as_slice());
                blk.push(0);
            }

            blk.push(0);

            cb(blk.as_mut_ptr() as *mut c_void)
        }
        _ => cb(ptr::mut_null())
    }
}

#[cfg(windows)]
fn with_dirp<T>(d: Option<&Path>, cb: |*u16| -> T) -> T {
    match d {
      Some(dir) => match dir.as_str() {
          Some(dir_str) => os::win32::as_utf16_p(dir_str, cb),
          None => cb(ptr::null())
      },
      None => cb(ptr::null())
    }
}

#[cfg(windows)]
fn free_handle(handle: *()) {
    assert!(unsafe {
        libc::CloseHandle(mem::transmute(handle)) != 0
    })
}

#[cfg(unix)]
fn free_handle(_handle: *()) {
    // unix has no process handle object, just a pid
}

#[cfg(unix)]
fn translate_status(status: c_int) -> p::ProcessExit {
    #[cfg(target_os = "linux")]
    #[cfg(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(target_os = "macos")]
    #[cfg(target_os = "freebsd")]
    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) {
        p::ExitStatus(imp::WEXITSTATUS(status) as int)
    } else {
        p::ExitSignal(imp::WTERMSIG(status) as int)
    }
}

/**
 * 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.
 */
fn waitpid(pid: pid_t) -> p::ProcessExit {
    return waitpid_os(pid);

    #[cfg(windows)]
    fn waitpid_os(pid: pid_t) -> p::ProcessExit {
        use libc::types::os::arch::extra::DWORD;
        use libc::consts::os::extra::{
            SYNCHRONIZE,
            PROCESS_QUERY_INFORMATION,
            FALSE,
            STILL_ACTIVE,
            INFINITE,
            WAIT_FAILED
        };
        use libc::funcs::extra::kernel32::{
            OpenProcess,
            GetExitCodeProcess,
            CloseHandle,
            WaitForSingleObject
        };

        unsafe {

            let process = OpenProcess(SYNCHRONIZE | PROCESS_QUERY_INFORMATION,
                                      FALSE,
                                      pid as DWORD);
            if process.is_null() {
                fail!("failure in OpenProcess: {}", os::last_os_error());
            }

            loop {
                let mut status = 0;
                if GetExitCodeProcess(process, &mut status) == FALSE {
                    assert!(CloseHandle(process) != 0);
                    fail!("failure in GetExitCodeProcess: {}", os::last_os_error());
                }
                if status != STILL_ACTIVE {
                    assert!(CloseHandle(process) != 0);
                    return p::ExitStatus(status as int);
                }
                if WaitForSingleObject(process, INFINITE) == WAIT_FAILED {
                    assert!(CloseHandle(process) != 0);
                    fail!("failure in WaitForSingleObject: {}", os::last_os_error());
                }
            }
        }
    }

    #[cfg(unix)]
    fn waitpid_os(pid: pid_t) -> p::ProcessExit {
        use libc::funcs::posix01::wait;
        let mut status = 0 as c_int;
        match retry(|| unsafe { wait::waitpid(pid, &mut status, 0) }) {
            -1 => fail!("unknown waitpid error: {}", super::last_error()),
            _ => translate_status(status),
        }
    }
}

fn waitpid_nowait(pid: pid_t) -> Option<p::ProcessExit> {
    return waitpid_os(pid);

    // This code path isn't necessary on windows
    #[cfg(windows)]
    fn waitpid_os(_pid: pid_t) -> Option<p::ProcessExit> { None }

    #[cfg(unix)]
    fn waitpid_os(pid: pid_t) -> Option<p::ProcessExit> {
        use libc::funcs::posix01::wait;
        let mut status = 0 as c_int;
        match retry(|| unsafe {
            wait::waitpid(pid, &mut status, libc::WNOHANG)
        }) {
            n if n == pid => Some(translate_status(status)),
            0 => None,
            n => fail!("unknown waitpid error `{}`: {}", n, super::last_error()),
        }
    }
}

#[cfg(test)]
mod tests {

    #[test] #[cfg(windows)]
    fn test_make_command_line() {
        use super::make_command_line;
        assert_eq!(
            make_command_line("prog", ["aaa".to_owned(), "bbb".to_owned(), "ccc".to_owned()]),
            "prog aaa bbb ccc".to_owned()
        );
        assert_eq!(
            make_command_line("C:\\Program Files\\blah\\blah.exe", ["aaa".to_owned()]),
            "\"C:\\Program Files\\blah\\blah.exe\" aaa".to_owned()
        );
        assert_eq!(
            make_command_line("C:\\Program Files\\test", ["aa\"bb".to_owned()]),
            "\"C:\\Program Files\\test\" aa\\\"bb".to_owned()
        );
        assert_eq!(
            make_command_line("echo", ["a b c".to_owned()]),
            "echo \"a b c\"".to_owned()
        );
        assert_eq!(
            make_command_line("\u03c0\u042f\u97f3\u00e6\u221e", []),
            "\u03c0\u042f\u97f3\u00e6\u221e".to_owned()
        );
    }
}