process.rs.html -- source
Description: Source to the Rust file `src/libstd/sys/unix/process.rs`.
Keywords: rust, rustlang, rust-lang

      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210
    211
    212
    213
    214
    215
    216
    217
    218
    219
    220
    221
    222
    223
    224
    225
    226
    227
    228
    229
    230
    231
    232
    233
    234
    235
    236
    237
    238
    239
    240
    241
    242
    243
    244
    245
    246
    247
    248
    249
    250
    251
    252
    253
    254
    255
    256
    257
    258
    259
    260
    261
    262
    263
    264
    265
    266
    267
    268
    269
    270
    271
    272
    273
    274
    275
    276
    277
    278
    279
    280
    281
    282
    283
    284
    285
    286
    287
    288
    289
    290
    291
    292
    293
    294
    295
    296
    297
    298
    299
    300
    301
    302
    303
    304
    305
    306
    307
    308
    309
    310
    311
    312
    313
    314
    315
    316
    317
    318
    319
    320
    321
    322
    323
    324
    325
    326
    327
    328
    329
    330
    331
    332
    333
    334
    335
    336
    337
    338
    339
    340
    341
    342
    343
    344
    345
    346
    347
    348
    349
    350
    351
    352
    353
    354
    355
    356
    357
    358
    359
    360
    361
    362
    363
    364
    365
    366
    367
    368
    369
    370
    371
    372
    373
    374
    375
    376
    377
    378
    379
    380
    381
    382
    383
    384
    385
    386
    387
    388
    389
    390
    391
    392
    393
    394
    395
    396
    397
    398
    399
    400
    401
    402
    403
    404
    405
    406
    407
    408
    409
    410
    411
    412
    413
    414
    415
    416
    417
    418
    419
    420
    421
    422
    423
    424
    425
    426
    427
    428
    429
    430
    431
    432
    433
    434
    435
    436
    437
    438
    439
    440
    441
    442
    443
    444
    445
    446
    447
    448
    449
    450
    451
    452
    453
    454
    455
    456
    457
    458
    459
    460
    461
    462
    463
    464
    465
    466
    467
    468
    469
    470
    471
    472
    473
    474
    475
    476
    477
    478
    479
    480
    481
    482
    483
    484
    485
    486
    487
    488
    489
    490
    491
    492
    493
    494
    495
    496
    497
    498
    499
    500
    501
    502
    503
    504
    505
    506
    507
    508
    509
    510
    511
    512
    513
    514
    515
    516
    517
    518
    519
    520
    521
    522
    523
    524
    525
    526
    527
    528
    529
    530
    531
    532
    533
    534
    535
    536
    537
    538
    539
    540
    541
    542
    543
    544
    545
    546
    547
    548
    549
    550
    551
    552
    553
    554
    555
    556
    557
    558
    559
    560
    561
    562
    563
    564
    565
    566
    567
    568
    569
    570
    571
    572
    573
    574
    575
    576
    577
    578
    579
    580
    581
    582
    583
    584
    585
    586
    587
    588
    589
    590
    591
    592
    593
    594
    595
    596
    597
    598
    599
    600
    601
    602
    603
    604
    605
    606
    607
    608
    609
    610
    611
    612
    613
    614
    615
    616
    617
    618
    619
    620
    621
    622
    623
    624
    625
    626
    627
    628
    629
    630
    631
    632
    633
    634
    635
    636
    637
    638
    639
    640
    641
    642
    643
    644
    645
    646
    647
    648
    649
    650
    651
    652
    653
    654
    655
    656
    657
    658
    659
    660
    661
    662
    663
    664
    665
    666
    667
    668
    669
    670
    671

    // Copyright 2014-2015 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 os::unix::prelude::*;

    use collections::hash_map::{HashMap, Entry};
    use env;
    use ffi::{OsString, OsStr, CString, CStr};
    use fmt;
    use io::{self, Error, ErrorKind};
    use libc::{self, pid_t, c_int, gid_t, uid_t, c_char};
    use mem;
    use ptr;
    use sys::fd::FileDesc;
    use sys::fs::{File, OpenOptions};
    use sys::pipe::{self, AnonPipe};
    use sys::{self, cvt, cvt_r};

    ////////////////////////////////////////////////////////////////////////////////
    // Command
    ////////////////////////////////////////////////////////////////////////////////

    pub struct Command {
        // Currently we try hard to ensure that the call to `.exec()` doesn't
        // actually allocate any memory. While many platforms try to ensure that
        // memory allocation works after a fork in a multithreaded process, it's
        // been observed to be buggy and somewhat unreliable, so we do our best to
        // just not do it at all!
        //
        // Along those lines, the `argv` and `envp` raw pointers here are exactly
        // what's gonna get passed to `execvp`. The `argv` array starts with the
        // `program` and ends with a NULL, and the `envp` pointer, if present, is
        // also null-terminated.
        //
        // Right now we don't support removing arguments, so there's no much fancy
        // support there, but we support adding and removing environment variables,
        // so a side table is used to track where in the `envp` array each key is
        // located. Whenever we add a key we update it in place if it's already
        // present, and whenever we remove a key we update the locations of all
        // other keys.
        program: CString,
        args: Vec<CString>,
        env: Option<HashMap<OsString, (usize, CString)>>,
        argv: Vec<*const c_char>,
        envp: Option<Vec<*const c_char>>,

        cwd: Option<CString>,
        uid: Option<uid_t>,
        gid: Option<gid_t>,
        saw_nul: bool,
        closures: Vec<Box<FnMut() -> io::Result<()> + Send + Sync>>,
        stdin: Option<Stdio>,
        stdout: Option<Stdio>,
        stderr: Option<Stdio>,
    }

    // passed back to std::process with the pipes connected to the child, if any
    // were requested
    pub struct StdioPipes {
        pub stdin: Option<AnonPipe>,
        pub stdout: Option<AnonPipe>,
        pub stderr: Option<AnonPipe>,
    }

    // passed to do_exec() with configuration of what the child stdio should look
    // like
    struct ChildPipes {
        stdin: ChildStdio,
        stdout: ChildStdio,
        stderr: ChildStdio,
    }

    enum ChildStdio {
        Inherit,
        Explicit(c_int),
        Owned(FileDesc),
    }

    pub enum Stdio {
        Inherit,
        Null,
        MakePipe,
        Fd(FileDesc),
    }

    impl Command {
        pub fn new(program: &OsStr) -> Command {
            let mut saw_nul = false;
            let program = os2c(program, &mut saw_nul);
            Command {
                argv: vec![program.as_ptr(), ptr::null()],
                program: program,
                args: Vec::new(),
                env: None,
                envp: None,
                cwd: None,
                uid: None,
                gid: None,
                saw_nul: saw_nul,
                closures: Vec::new(),
                stdin: None,
                stdout: None,
                stderr: None,
            }
        }

        pub fn arg(&mut self, arg: &OsStr) {
            // Overwrite the trailing NULL pointer in `argv` and then add a new null
            // pointer.
            let arg = os2c(arg, &mut self.saw_nul);
            self.argv[self.args.len() + 1] = arg.as_ptr();
            self.argv.push(ptr::null());

            // Also make sure we keep track of the owned value to schedule a
            // destructor for this memory.
            self.args.push(arg);
        }

        fn init_env_map(&mut self) -> (&mut HashMap<OsString, (usize, CString)>,
                                       &mut Vec<*const c_char>) {
            if self.env.is_none() {
                let mut map = HashMap::new();
                let mut envp = Vec::new();
                for (k, v) in env::vars_os() {
                    let s = pair_to_key(&k, &v, &mut self.saw_nul);
                    envp.push(s.as_ptr());
                    map.insert(k, (envp.len() - 1, s));
                }
                envp.push(ptr::null());
                self.env = Some(map);
                self.envp = Some(envp);
            }
            (self.env.as_mut().unwrap(), self.envp.as_mut().unwrap())
        }

        pub fn env(&mut self, key: &OsStr, val: &OsStr) {
            let new_key = pair_to_key(key, val, &mut self.saw_nul);
            let (map, envp) = self.init_env_map();

            // If `key` is already present then we just update `envp` in place
            // (and store the owned value), but if it's not there we override the
            // trailing NULL pointer, add a new NULL pointer, and store where we
            // were located.
            match map.entry(key.to_owned()) {
                Entry::Occupied(mut e) => {
                    let (i, ref mut s) = *e.get_mut();
                    envp[i] = new_key.as_ptr();
                    *s = new_key;
                }
                Entry::Vacant(e) => {
                    let len = envp.len();
                    envp[len - 1] = new_key.as_ptr();
                    envp.push(ptr::null());
                    e.insert((len - 1, new_key));
                }
            }
        }

        pub fn env_remove(&mut self, key: &OsStr) {
            let (map, envp) = self.init_env_map();

            // If we actually ended up removing a key, then we need to update the
            // position of all keys that come after us in `envp` because they're all
            // one element sooner now.
            if let Some((i, _)) = map.remove(key) {
                envp.remove(i);

                for (_, &mut (ref mut j, _)) in map.iter_mut() {
                    if *j >= i {
                        *j -= 1;
                    }
                }
            }
        }

        pub fn env_clear(&mut self) {
            self.env = Some(HashMap::new());
            self.envp = Some(vec![ptr::null()]);
        }

        pub fn cwd(&mut self, dir: &OsStr) {
            self.cwd = Some(os2c(dir, &mut self.saw_nul));
        }
        pub fn uid(&mut self, id: uid_t) {
            self.uid = Some(id);
        }
        pub fn gid(&mut self, id: gid_t) {
            self.gid = Some(id);
        }

        pub fn before_exec(&mut self,
                           f: Box<FnMut() -> io::Result<()> + Send + Sync>) {
            self.closures.push(f);
        }

        pub fn stdin(&mut self, stdin: Stdio) {
            self.stdin = Some(stdin);
        }
        pub fn stdout(&mut self, stdout: Stdio) {
            self.stdout = Some(stdout);
        }
        pub fn stderr(&mut self, stderr: Stdio) {
            self.stderr = Some(stderr);
        }

        pub fn spawn(&mut self, default: Stdio, needs_stdin: bool)
                     -> io::Result<(Process, StdioPipes)> {
            const CLOEXEC_MSG_FOOTER: &'static [u8] = b"NOEX";

            if self.saw_nul {
                return Err(io::Error::new(ErrorKind::InvalidInput,
                                          "nul byte found in provided data"));
            }

            let (ours, theirs) = self.setup_io(default, needs_stdin)?;
            let (input, output) = sys::pipe::anon_pipe()?;

            let pid = unsafe {
                match cvt(libc::fork())? {
                    0 => {
                        drop(input);
                        let err = self.do_exec(theirs);
                        let errno = err.raw_os_error().unwrap_or(libc::EINVAL) as u32;
                        let bytes = [
                            (errno >> 24) as u8,
                            (errno >> 16) as u8,
                            (errno >>  8) as u8,
                            (errno >>  0) as u8,
                            CLOEXEC_MSG_FOOTER[0], CLOEXEC_MSG_FOOTER[1],
                            CLOEXEC_MSG_FOOTER[2], CLOEXEC_MSG_FOOTER[3]
                        ];
                        // pipe I/O up to PIPE_BUF bytes should be atomic, and then
                        // we want to be sure we *don't* run at_exit destructors as
                        // we're being torn down regardless
                        assert!(output.write(&bytes).is_ok());
                        libc::_exit(1)
                    }
                    n => n,
                }
            };

            let mut p = Process { pid: pid, status: None };
            drop(output);
            let mut bytes = [0; 8];

            // loop to handle EINTR
            loop {
                match input.read(&mut bytes) {
                    Ok(0) => return Ok((p, ours)),
                    Ok(8) => {
                        assert!(combine(CLOEXEC_MSG_FOOTER) == combine(&bytes[4.. 8]),
                                "Validation on the CLOEXEC pipe failed: {:?}", bytes);
                        let errno = combine(&bytes[0.. 4]);
                        assert!(p.wait().is_ok(),
                                "wait() should either return Ok or panic");
                        return Err(Error::from_raw_os_error(errno))
                    }
                    Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
                    Err(e) => {
                        assert!(p.wait().is_ok(),
                                "wait() should either return Ok or panic");
                        panic!("the CLOEXEC pipe failed: {:?}", e)
                    },
                    Ok(..) => { // pipe I/O up to PIPE_BUF bytes should be atomic
                        assert!(p.wait().is_ok(),
                                "wait() should either return Ok or panic");
                        panic!("short read on the CLOEXEC pipe")
                    }
                }
            }

            fn combine(arr: &[u8]) -> i32 {
                let a = arr[0] as u32;
                let b = arr[1] as u32;
                let c = arr[2] as u32;
                let d = arr[3] as u32;

                ((a << 24) | (b << 16) | (c << 8) | (d << 0)) as i32
            }
        }

        pub fn exec(&mut self, default: Stdio) -> io::Error {
            if self.saw_nul {
                return io::Error::new(ErrorKind::InvalidInput,
                                      "nul byte found in provided data")
            }

            match self.setup_io(default, true) {
                Ok((_, theirs)) => unsafe { self.do_exec(theirs) },
                Err(e) => e,
            }
        }

        // 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)
        unsafe fn do_exec(&mut self, stdio: ChildPipes) -> io::Error {
            macro_rules! t {
                ($e:expr) => (match $e {
                    Ok(e) => e,
                    Err(e) => return e,
                })
            }

            if let Some(fd) = stdio.stdin.fd() {
                t!(cvt_r(|| libc::dup2(fd, libc::STDIN_FILENO)));
            }
            if let Some(fd) = stdio.stdout.fd() {
                t!(cvt_r(|| libc::dup2(fd, libc::STDOUT_FILENO)));
            }
            if let Some(fd) = stdio.stderr.fd() {
                t!(cvt_r(|| libc::dup2(fd, libc::STDERR_FILENO)));
            }

            if let Some(u) = self.gid {
                t!(cvt(libc::setgid(u as gid_t)));
            }
            if let Some(u) = self.uid {
                // 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.
                let _ = libc::setgroups(0, ptr::null());

                t!(cvt(libc::setuid(u as uid_t)));
            }
            if let Some(ref cwd) = self.cwd {
                t!(cvt(libc::chdir(cwd.as_ptr())));
            }
            if let Some(ref envp) = self.envp {
                *sys::os::environ() = envp.as_ptr();
            }

            // NaCl has no signal support.
            if cfg!(not(any(target_os = "nacl", target_os = "emscripten"))) {
                // Reset signal handling so the child process starts in a
                // standardized state. libstd ignores SIGPIPE, and signal-handling
                // libraries often set a mask. Child processes inherit ignored
                // signals and the signal mask from their parent, but most
                // UNIX programs do not reset these things on their own, so we
                // need to clean things up now to avoid confusing the program
                // we're about to run.
                let mut set: libc::sigset_t = mem::uninitialized();
                t!(cvt(libc::sigemptyset(&mut set)));
                t!(cvt(libc::pthread_sigmask(libc::SIG_SETMASK, &set,
                                             ptr::null_mut())));
                let ret = super::signal(libc::SIGPIPE, libc::SIG_DFL);
                if ret == libc::SIG_ERR {
                    return io::Error::last_os_error()
                }
            }

            for callback in self.closures.iter_mut() {
                t!(callback());
            }

            libc::execvp(self.argv[0], self.argv.as_ptr());
            io::Error::last_os_error()
        }

        fn setup_io(&self, default: Stdio, needs_stdin: bool)
                    -> io::Result<(StdioPipes, ChildPipes)> {
            let null = Stdio::Null;
            let default_stdin = if needs_stdin {&default} else {&null};
            let stdin = self.stdin.as_ref().unwrap_or(default_stdin);
            let stdout = self.stdout.as_ref().unwrap_or(&default);
            let stderr = self.stderr.as_ref().unwrap_or(&default);
            let (their_stdin, our_stdin) = stdin.to_child_stdio(true)?;
            let (their_stdout, our_stdout) = stdout.to_child_stdio(false)?;
            let (their_stderr, our_stderr) = stderr.to_child_stdio(false)?;
            let ours = StdioPipes {
                stdin: our_stdin,
                stdout: our_stdout,
                stderr: our_stderr,
            };
            let theirs = ChildPipes {
                stdin: their_stdin,
                stdout: their_stdout,
                stderr: their_stderr,
            };
            Ok((ours, theirs))
        }
    }

    fn os2c(s: &OsStr, saw_nul: &mut bool) -> CString {
        CString::new(s.as_bytes()).unwrap_or_else(|_e| {
            *saw_nul = true;
            CString::new("<string-with-nul>").unwrap()
        })
    }

    impl Stdio {
        fn to_child_stdio(&self, readable: bool)
                          -> io::Result<(ChildStdio, Option<AnonPipe>)> {
            match *self {
                Stdio::Inherit => Ok((ChildStdio::Inherit, None)),

                // Make sure that the source descriptors are not an stdio
                // descriptor, otherwise the order which we set the child's
                // descriptors may blow away a descriptor which we are hoping to
                // save. For example, suppose we want the child's stderr to be the
                // parent's stdout, and the child's stdout to be the parent's
                // stderr. No matter which we dup first, the second will get
                // overwritten prematurely.
                Stdio::Fd(ref fd) => {
                    if fd.raw() >= 0 && fd.raw() <= libc::STDERR_FILENO {
                        Ok((ChildStdio::Owned(fd.duplicate()?), None))
                    } else {
                        Ok((ChildStdio::Explicit(fd.raw()), None))
                    }
                }

                Stdio::MakePipe => {
                    let (reader, writer) = pipe::anon_pipe()?;
                    let (ours, theirs) = if readable {
                        (writer, reader)
                    } else {
                        (reader, writer)
                    };
                    Ok((ChildStdio::Owned(theirs.into_fd()), Some(ours)))
                }

                Stdio::Null => {
                    let mut opts = OpenOptions::new();
                    opts.read(readable);
                    opts.write(!readable);
                    let path = unsafe {
                        CStr::from_ptr("/dev/null\0".as_ptr() as *const _)
                    };
                    let fd = File::open_c(&path, &opts)?;
                    Ok((ChildStdio::Owned(fd.into_fd()), None))
                }
            }
        }
    }

    impl ChildStdio {
        fn fd(&self) -> Option<c_int> {
            match *self {
                ChildStdio::Inherit => None,
                ChildStdio::Explicit(fd) => Some(fd),
                ChildStdio::Owned(ref fd) => Some(fd.raw()),
            }
        }
    }

    fn pair_to_key(key: &OsStr, value: &OsStr, saw_nul: &mut bool) -> CString {
        let (key, value) = (key.as_bytes(), value.as_bytes());
        let mut v = Vec::with_capacity(key.len() + value.len() + 1);
        v.extend(key);
        v.push(b'=');
        v.extend(value);
        CString::new(v).unwrap_or_else(|_e| {
            *saw_nul = true;
            CString::new("foo=bar").unwrap()
        })
    }

    impl fmt::Debug for Command {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            write!(f, "{:?}", self.program)?;
            for arg in &self.args {
                write!(f, " {:?}", arg)?;
            }
            Ok(())
        }
    }

    ////////////////////////////////////////////////////////////////////////////////
    // Processes
    ////////////////////////////////////////////////////////////////////////////////

    /// Unix exit statuses
    #[derive(PartialEq, Eq, Clone, Copy, Debug)]
    pub struct ExitStatus(c_int);

    impl ExitStatus {
        fn exited(&self) -> bool {
            unsafe { libc::WIFEXITED(self.0) }
        }

        pub fn success(&self) -> bool {
            self.code() == Some(0)
        }

        pub fn code(&self) -> Option<i32> {
            if self.exited() {
                Some(unsafe { libc::WEXITSTATUS(self.0) })
            } else {
                None
            }
        }

        pub fn signal(&self) -> Option<i32> {
            if !self.exited() {
                Some(unsafe { libc::WTERMSIG(self.0) })
            } else {
                None
            }
        }
    }

    impl From<c_int> for ExitStatus {
        fn from(a: c_int) -> ExitStatus {
            ExitStatus(a)
        }
    }

    impl fmt::Display for ExitStatus {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            if let Some(code) = self.code() {
                write!(f, "exit code: {}", code)
            } else {
                let signal = self.signal().unwrap();
                write!(f, "signal: {}", signal)
            }
        }
    }

    /// The unique id of the process (this should never be negative).
    pub struct Process {
        pid: pid_t,
        status: Option<ExitStatus>,
    }

    impl Process {
        pub fn id(&self) -> u32 {
            self.pid as u32
        }

        pub fn kill(&mut self) -> io::Result<()> {
            // If we've already waited on this process then the pid can be recycled
            // and used for another process, and we probably shouldn't be killing
            // random processes, so just return an error.
            if self.status.is_some() {
                Err(Error::new(ErrorKind::InvalidInput,
                               "invalid argument: can't kill an exited process"))
            } else {
                cvt(unsafe { libc::kill(self.pid, libc::SIGKILL) }).map(|_| ())
            }
        }

        pub fn wait(&mut self) -> io::Result<ExitStatus> {
            if let Some(status) = self.status {
                return Ok(status)
            }
            let mut status = 0 as c_int;
            cvt_r(|| unsafe { libc::waitpid(self.pid, &mut status, 0) })?;
            self.status = Some(ExitStatus(status));
            Ok(ExitStatus(status))
        }
    }

    #[cfg(all(test, not(target_os = "emscripten")))]
    mod tests {
        use super::*;

        use ffi::OsStr;
        use mem;
        use ptr;
        use libc;
        use sys::cvt;

        macro_rules! t {
            ($e:expr) => {
                match $e {
                    Ok(t) => t,
                    Err(e) => panic!("received error for `{}`: {}", stringify!($e), e),
                }
            }
        }

        #[cfg(not(target_os = "android"))]
        extern {
            #[cfg_attr(target_os = "netbsd", link_name = "__sigaddset14")]
            fn sigaddset(set: *mut libc::sigset_t, signum: libc::c_int) -> libc::c_int;
        }

        #[cfg(target_os = "android")]
        unsafe fn sigaddset(set: *mut libc::sigset_t, signum: libc::c_int) -> libc::c_int {
            use slice;

            let raw = slice::from_raw_parts_mut(set as *mut u8, mem::size_of::<libc::sigset_t>());
            let bit = (signum - 1) as usize;
            raw[bit / 8] |= 1 << (bit % 8);
            return 0;
        }

        // See #14232 for more information, but it appears that signal delivery to a
        // newly spawned process may just be raced in the OSX, so to prevent this
        // test from being flaky we ignore it on OSX.
        #[test]
        #[cfg_attr(target_os = "macos", ignore)]
        #[cfg_attr(target_os = "nacl", ignore)] // no signals on NaCl.
        fn test_process_mask() {
            unsafe {
                // Test to make sure that a signal mask does not get inherited.
                let mut cmd = Command::new(OsStr::new("cat"));

                let mut set: libc::sigset_t = mem::uninitialized();
                let mut old_set: libc::sigset_t = mem::uninitialized();
                t!(cvt(libc::sigemptyset(&mut set)));
                t!(cvt(sigaddset(&mut set, libc::SIGINT)));
                t!(cvt(libc::pthread_sigmask(libc::SIG_SETMASK, &set, &mut old_set)));

                cmd.stdin(Stdio::MakePipe);
                cmd.stdout(Stdio::MakePipe);

                let (mut cat, mut pipes) = t!(cmd.spawn(Stdio::Null, true));
                let stdin_write = pipes.stdin.take().unwrap();
                let stdout_read = pipes.stdout.take().unwrap();

                t!(cvt(libc::pthread_sigmask(libc::SIG_SETMASK, &old_set,
                                             ptr::null_mut())));

                t!(cvt(libc::kill(cat.id() as libc::pid_t, libc::SIGINT)));
                // We need to wait until SIGINT is definitely delivered. The
                // easiest way is to write something to cat, and try to read it
                // back: if SIGINT is unmasked, it'll get delivered when cat is
                // next scheduled.
                let _ = stdin_write.write(b"Hello");
                drop(stdin_write);

                // Either EOF or failure (EPIPE) is okay.
                let mut buf = [0; 5];
                if let Ok(ret) = stdout_read.read(&mut buf) {
                    assert!(ret == 0);
                }

                t!(cat.wait());
            }
        }
    }

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result
+
  Collapse/expand all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)