library/std/src/sys/windows/process.rs

   1 #![unstable(feature = "process_internals", issue = "none")]
   2
   3 #[cfg(test)]
   4 mod tests;
   5
   6 use crate::cmp;
   7 use crate::collections::BTreeMap;
   8 use crate::env;
   9 use crate::env::consts::{EXE_EXTENSION, EXE_SUFFIX};
  10 use crate::ffi::{OsStr, OsString};
  11 use crate::fmt;
  12 use crate::io::{self, Error, ErrorKind};
  13 use crate::mem;
  14 use crate::num::NonZeroI32;
  15 use crate::os::windows::ffi::{OsStrExt, OsStringExt};
  16 use crate::os::windows::io::{AsHandle, AsRawHandle, BorrowedHandle, FromRawHandle, IntoRawHandle};
  17 use crate::path::{Path, PathBuf};
  18 use crate::ptr;
  19 use crate::sync::Mutex;
  20 use crate::sys::args::{self, Arg};
  21 use crate::sys::c;
  22 use crate::sys::c::NonZeroDWORD;
  23 use crate::sys::cvt;
  24 use crate::sys::fs::{File, OpenOptions};
  25 use crate::sys::handle::Handle;
  26 use crate::sys::path;
  27 use crate::sys::pipe::{self, AnonPipe};
  28 use crate::sys::stdio;
  29 use crate::sys_common::process::{CommandEnv, CommandEnvs};
  30 use crate::sys_common::IntoInner;
  31
  32 use libc::{c_void, EXIT_FAILURE, EXIT_SUCCESS};
  33
  34 ////////////////////////////////////////////////////////////////////////////////
  35 // Command
  36 ////////////////////////////////////////////////////////////////////////////////
  37
  38 #[derive(Clone, Debug, Eq)]
  39 #[doc(hidden)]
  40 pub struct EnvKey {
  41     os_string: OsString,
  42     // This stores a UTF-16 encoded string to workaround the mismatch between
  43     // Rust's OsString (WTF-8) and the Windows API string type (UTF-16).
  44     // Normally converting on every API call is acceptable but here
  45     // `c::CompareStringOrdinal` will be called for every use of `==`.
  46     utf16: Vec<u16>,
  47 }
  48
  49 impl EnvKey {
  50     fn new<T: Into<OsString>>(key: T) -> Self {
  51         EnvKey::from(key.into())
  52     }
  53 }
  54
  55 // Comparing Windows environment variable keys[1] are behaviourally the
  56 // composition of two operations[2]:
  57 //
  58 // 1. Case-fold both strings. This is done using a language-independent
  59 // uppercase mapping that's unique to Windows (albeit based on data from an
  60 // older Unicode spec). It only operates on individual UTF-16 code units so
  61 // surrogates are left unchanged. This uppercase mapping can potentially change
  62 // between Windows versions.
  63 //
  64 // 2. Perform an ordinal comparison of the strings. A comparison using ordinal
  65 // is just a comparison based on the numerical value of each UTF-16 code unit[3].
  66 //
  67 // Because the case-folding mapping is unique to Windows and not guaranteed to
  68 // be stable, we ask the OS to compare the strings for us. This is done by
  69 // calling `CompareStringOrdinal`[4] with `bIgnoreCase` set to `TRUE`.
  70 //
  71 // [1] https://docs.microsoft.com/en-us/dotnet/standard/base-types/best-practices-strings#choosing-a-stringcomparison-member-for-your-method-call
  72 // [2] https://docs.microsoft.com/en-us/dotnet/standard/base-types/best-practices-strings#stringtoupper-and-stringtolower
  73 // [3] https://docs.microsoft.com/en-us/dotnet/api/system.stringcomparison?view=net-5.0#System_StringComparison_Ordinal
  74 // [4] https://docs.microsoft.com/en-us/windows/win32/api/stringapiset/nf-stringapiset-comparestringordinal
  75 impl Ord for EnvKey {
  76     fn cmp(&self, other: &Self) -> cmp::Ordering {
  77         unsafe {
  78             let result = c::CompareStringOrdinal(
  79                 self.utf16.as_ptr(),
  80                 self.utf16.len() as _,
  81                 other.utf16.as_ptr(),
  82                 other.utf16.len() as _,
  83                 c::TRUE,
  84             );
  85             match result {
  86                 c::CSTR_LESS_THAN => cmp::Ordering::Less,
  87                 c::CSTR_EQUAL => cmp::Ordering::Equal,
  88                 c::CSTR_GREATER_THAN => cmp::Ordering::Greater,
  89                 // `CompareStringOrdinal` should never fail so long as the parameters are correct.
  90                 _ => panic!("comparing environment keys failed: {}", Error::last_os_error()),
  91             }
  92         }
  93     }
  94 }
  95 impl PartialOrd for EnvKey {
  96     fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
  97         Some(self.cmp(other))
  98     }
  99 }
 100 impl PartialEq for EnvKey {
 101     fn eq(&self, other: &Self) -> bool {
 102         if self.utf16.len() != other.utf16.len() {
 103             false
 104         } else {
 105             self.cmp(other) == cmp::Ordering::Equal
 106         }
 107     }
 108 }
 109 impl PartialOrd<str> for EnvKey {
 110     fn partial_cmp(&self, other: &str) -> Option<cmp::Ordering> {
 111         Some(self.cmp(&EnvKey::new(other)))
 112     }
 113 }
 114 impl PartialEq<str> for EnvKey {
 115     fn eq(&self, other: &str) -> bool {
 116         if self.os_string.len() != other.len() {
 117             false
 118         } else {
 119             self.cmp(&EnvKey::new(other)) == cmp::Ordering::Equal
 120         }
 121     }
 122 }
 123
 124 // Environment variable keys should preserve their original case even though
 125 // they are compared using a caseless string mapping.
 126 impl From<OsString> for EnvKey {
 127     fn from(k: OsString) -> Self {
 128         EnvKey { utf16: k.encode_wide().collect(), os_string: k }
 129     }
 130 }
 131
 132 impl From<EnvKey> for OsString {
 133     fn from(k: EnvKey) -> Self {
 134         k.os_string
 135     }
 136 }
 137
 138 impl From<&OsStr> for EnvKey {
 139     fn from(k: &OsStr) -> Self {
 140         Self::from(k.to_os_string())
 141     }
 142 }
 143
 144 impl AsRef<OsStr> for EnvKey {
 145     fn as_ref(&self) -> &OsStr {
 146         &self.os_string
 147     }
 148 }
 149
 150 pub(crate) fn ensure_no_nuls<T: AsRef<OsStr>>(str: T) -> io::Result<T> {
 151     if str.as_ref().encode_wide().any(|b| b == 0) {
 152         Err(io::const_io_error!(ErrorKind::InvalidInput, "nul byte found in provided data"))
 153     } else {
 154         Ok(str)
 155     }
 156 }
 157
 158 pub struct Command {
 159     program: OsString,
 160     args: Vec<Arg>,
 161     env: CommandEnv,
 162     cwd: Option<OsString>,
 163     flags: u32,
 164     detach: bool, // not currently exposed in std::process
 165     stdin: Option<Stdio>,
 166     stdout: Option<Stdio>,
 167     stderr: Option<Stdio>,
 168     force_quotes_enabled: bool,
 169 }
 170
 171 pub enum Stdio {
 172     Inherit,
 173     Null,
 174     MakePipe,
 175     Pipe(AnonPipe),
 176     Handle(Handle),
 177 }
 178
 179 pub struct StdioPipes {
 180     pub stdin: Option<AnonPipe>,
 181     pub stdout: Option<AnonPipe>,
 182     pub stderr: Option<AnonPipe>,
 183 }
 184
 185 impl Command {
 186     pub fn new(program: &OsStr) -> Command {
 187         Command {
 188             program: program.to_os_string(),
 189             args: Vec::new(),
 190             env: Default::default(),
 191             cwd: None,
 192             flags: 0,
 193             detach: false,
 194             stdin: None,
 195             stdout: None,
 196             stderr: None,
 197             force_quotes_enabled: false,
 198         }
 199     }
 200
 201     pub fn arg(&mut self, arg: &OsStr) {
 202         self.args.push(Arg::Regular(arg.to_os_string()))
 203     }
 204     pub fn env_mut(&mut self) -> &mut CommandEnv {
 205         &mut self.env
 206     }
 207     pub fn cwd(&mut self, dir: &OsStr) {
 208         self.cwd = Some(dir.to_os_string())
 209     }
 210     pub fn stdin(&mut self, stdin: Stdio) {
 211         self.stdin = Some(stdin);
 212     }
 213     pub fn stdout(&mut self, stdout: Stdio) {
 214         self.stdout = Some(stdout);
 215     }
 216     pub fn stderr(&mut self, stderr: Stdio) {
 217         self.stderr = Some(stderr);
 218     }
 219     pub fn creation_flags(&mut self, flags: u32) {
 220         self.flags = flags;
 221     }
 222
 223     pub fn force_quotes(&mut self, enabled: bool) {
 224         self.force_quotes_enabled = enabled;
 225     }
 226
 227     pub fn raw_arg(&mut self, command_str_to_append: &OsStr) {
 228         self.args.push(Arg::Raw(command_str_to_append.to_os_string()))
 229     }
 230
 231     pub fn get_program(&self) -> &OsStr {
 232         &self.program
 233     }
 234
 235     pub fn get_args(&self) -> CommandArgs<'_> {
 236         let iter = self.args.iter();
 237         CommandArgs { iter }
 238     }
 239
 240     pub fn get_envs(&self) -> CommandEnvs<'_> {
 241         self.env.iter()
 242     }
 243
 244     pub fn get_current_dir(&self) -> Option<&Path> {
 245         self.cwd.as_ref().map(|cwd| Path::new(cwd))
 246     }
 247
 248     pub fn spawn(
 249         &mut self,
 250         default: Stdio,
 251         needs_stdin: bool,
 252     ) -> io::Result<(Process, StdioPipes)> {
 253         let maybe_env = self.env.capture_if_changed();
 254
 255         let mut si = zeroed_startupinfo();
 256         si.cb = mem::size_of::<c::STARTUPINFO>() as c::DWORD;
 257         si.dwFlags = c::STARTF_USESTDHANDLES;
 258
 259         let child_paths = if let Some(env) = maybe_env.as_ref() {
 260             env.get(&EnvKey::new("PATH")).map(|s| s.as_os_str())
 261         } else {
 262             None
 263         };
 264         let program = resolve_exe(&self.program, || env::var_os("PATH"), child_paths)?;
 265         // Case insensitive "ends_with" of UTF-16 encoded ".bat" or ".cmd"
 266         let is_batch_file = matches!(
 267             program.len().checked_sub(5).and_then(|i| program.get(i..)),
 268             Some([46, 98 | 66, 97 | 65, 116 | 84, 0] | [46, 99 | 67, 109 | 77, 100 | 68, 0])
 269         );
 270         let (program, mut cmd_str) = if is_batch_file {
 271             (
 272                 command_prompt()?,
 273                 args::make_bat_command_line(
 274                     &args::to_user_path(program)?,
 275                     &self.args,
 276                     self.force_quotes_enabled,
 277                 )?,
 278             )
 279         } else {
 280             let cmd_str = make_command_line(&self.program, &self.args, self.force_quotes_enabled)?;
 281             (program, cmd_str)
 282         };
 283         cmd_str.push(0); // add null terminator
 284
 285         // stolen from the libuv code.
 286         let mut flags = self.flags | c::CREATE_UNICODE_ENVIRONMENT;
 287         if self.detach {
 288             flags |= c::DETACHED_PROCESS | c::CREATE_NEW_PROCESS_GROUP;
 289         }
 290
 291         let (envp, _data) = make_envp(maybe_env)?;
 292         let (dirp, _data) = make_dirp(self.cwd.as_ref())?;
 293         let mut pi = zeroed_process_information();
 294
 295         // Prepare all stdio handles to be inherited by the child. This
 296         // currently involves duplicating any existing ones with the ability to
 297         // be inherited by child processes. Note, however, that once an
 298         // inheritable handle is created, *any* spawned child will inherit that
 299         // handle. We only want our own child to inherit this handle, so we wrap
 300         // the remaining portion of this spawn in a mutex.
 301         //
 302         // For more information, msdn also has an article about this race:
 303         // https://support.microsoft.com/kb/315939
 304         static CREATE_PROCESS_LOCK: Mutex<()> = Mutex::new(());
 305
 306         let _guard = CREATE_PROCESS_LOCK.lock();
 307
 308         let mut pipes = StdioPipes { stdin: None, stdout: None, stderr: None };
 309         let null = Stdio::Null;
 310         let default_stdin = if needs_stdin { &default } else { &null };
 311         let stdin = self.stdin.as_ref().unwrap_or(default_stdin);
 312         let stdout = self.stdout.as_ref().unwrap_or(&default);
 313         let stderr = self.stderr.as_ref().unwrap_or(&default);
 314         let stdin = stdin.to_handle(c::STD_INPUT_HANDLE, &mut pipes.stdin)?;
 315         let stdout = stdout.to_handle(c::STD_OUTPUT_HANDLE, &mut pipes.stdout)?;
 316         let stderr = stderr.to_handle(c::STD_ERROR_HANDLE, &mut pipes.stderr)?;
 317         si.hStdInput = stdin.as_raw_handle();
 318         si.hStdOutput = stdout.as_raw_handle();
 319         si.hStdError = stderr.as_raw_handle();
 320
 321         unsafe {
 322             cvt(c::CreateProcessW(
 323                 program.as_ptr(),
 324                 cmd_str.as_mut_ptr(),
 325                 ptr::null_mut(),
 326                 ptr::null_mut(),
 327                 c::TRUE,
 328                 flags,
 329                 envp,
 330                 dirp,
 331                 &mut si,
 332                 &mut pi,
 333             ))
 334         }?;
 335
 336         unsafe {
 337             Ok((
 338                 Process {
 339                     handle: Handle::from_raw_handle(pi.hProcess),
 340                     main_thread_handle: Handle::from_raw_handle(pi.hThread),
 341                 },
 342                 pipes,
 343             ))
 344         }
 345     }
 346 }
 347
 348 impl fmt::Debug for Command {
 349     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 350         self.program.fmt(f)?;
 351         for arg in &self.args {
 352             f.write_str(" ")?;
 353             match arg {
 354                 Arg::Regular(s) => s.fmt(f),
 355                 Arg::Raw(s) => f.write_str(&s.to_string_lossy()),
 356             }?;
 357         }
 358         Ok(())
 359     }
 360 }
 361
 362 // Resolve `exe_path` to the executable name.
 363 //
 364 // * If the path is simply a file name then use the paths given by `search_paths` to find the executable.
 365 // * Otherwise use the `exe_path` as given.
 366 //
 367 // This function may also append `.exe` to the name. The rationale for doing so is as follows:
 368 //
 369 // It is a very strong convention that Windows executables have the `exe` extension.
 370 // In Rust, it is common to omit this extension.
 371 // Therefore this functions first assumes `.exe` was intended.
 372 // It falls back to the plain file name if a full path is given and the extension is omitted
 373 // or if only a file name is given and it already contains an extension.
 374 fn resolve_exe<'a>(
 375     exe_path: &'a OsStr,
 376     parent_paths: impl FnOnce() -> Option<OsString>,
 377     child_paths: Option<&OsStr>,
 378 ) -> io::Result<Vec<u16>> {
 379     // Early return if there is no filename.
 380     if exe_path.is_empty() || path::has_trailing_slash(exe_path) {
 381         return Err(io::const_io_error!(
 382             io::ErrorKind::InvalidInput,
 383             "program path has no file name",
 384         ));
 385     }
 386     // Test if the file name has the `exe` extension.
 387     // This does a case-insensitive `ends_with`.
 388     let has_exe_suffix = if exe_path.len() >= EXE_SUFFIX.len() {
 389         exe_path.bytes()[exe_path.len() - EXE_SUFFIX.len()..]
 390             .eq_ignore_ascii_case(EXE_SUFFIX.as_bytes())
 391     } else {
 392         false
 393     };
 394
 395     // If `exe_path` is an absolute path or a sub-path then don't search `PATH` for it.
 396     if !path::is_file_name(exe_path) {
 397         if has_exe_suffix {
 398             // The application name is a path to a `.exe` file.
 399             // Let `CreateProcessW` figure out if it exists or not.
 400             return path::maybe_verbatim(Path::new(exe_path));
 401         }
 402         let mut path = PathBuf::from(exe_path);
 403
 404         // Append `.exe` if not already there.
 405         path = path::append_suffix(path, EXE_SUFFIX.as_ref());
 406         if let Some(path) = program_exists(&path) {
 407             return Ok(path);
 408         } else {
 409             // It's ok to use `set_extension` here because the intent is to
 410             // remove the extension that was just added.
 411             path.set_extension("");
 412             return path::maybe_verbatim(&path);
 413         }
 414     } else {
 415         ensure_no_nuls(exe_path)?;
 416         // From the `CreateProcessW` docs:
 417         // > If the file name does not contain an extension, .exe is appended.
 418         // Note that this rule only applies when searching paths.
 419         let has_extension = exe_path.bytes().contains(&b'.');
 420
 421         // Search the directories given by `search_paths`.
 422         let result = search_paths(parent_paths, child_paths, |mut path| {
 423             path.push(&exe_path);
 424             if !has_extension {
 425                 path.set_extension(EXE_EXTENSION);
 426             }
 427             program_exists(&path)
 428         });
 429         if let Some(path) = result {
 430             return Ok(path);
 431         }
 432     }
 433     // If we get here then the executable cannot be found.
 434     Err(io::const_io_error!(io::ErrorKind::NotFound, "program not found"))
 435 }
 436
 437 // Calls `f` for every path that should be used to find an executable.
 438 // Returns once `f` returns the path to an executable or all paths have been searched.
 439 fn search_paths<Paths, Exists>(
 440     parent_paths: Paths,
 441     child_paths: Option<&OsStr>,
 442     mut exists: Exists,
 443 ) -> Option<Vec<u16>>
 444 where
 445     Paths: FnOnce() -> Option<OsString>,
 446     Exists: FnMut(PathBuf) -> Option<Vec<u16>>,
 447 {
 448     // 1. Child paths
 449     // This is for consistency with Rust's historic behaviour.
 450     if let Some(paths) = child_paths {
 451         for path in env::split_paths(paths).filter(|p| !p.as_os_str().is_empty()) {
 452             if let Some(path) = exists(path) {
 453                 return Some(path);
 454             }
 455         }
 456     }
 457
 458     // 2. Application path
 459     if let Ok(mut app_path) = env::current_exe() {
 460         app_path.pop();
 461         if let Some(path) = exists(app_path) {
 462             return Some(path);
 463         }
 464     }
 465
 466     // 3 & 4. System paths
 467     // SAFETY: This uses `fill_utf16_buf` to safely call the OS functions.
 468     unsafe {
 469         if let Ok(Some(path)) = super::fill_utf16_buf(
 470             |buf, size| c::GetSystemDirectoryW(buf, size),
 471             |buf| exists(PathBuf::from(OsString::from_wide(buf))),
 472         ) {
 473             return Some(path);
 474         }
 475         #[cfg(not(target_vendor = "uwp"))]
 476         {
 477             if let Ok(Some(path)) = super::fill_utf16_buf(
 478                 |buf, size| c::GetWindowsDirectoryW(buf, size),
 479                 |buf| exists(PathBuf::from(OsString::from_wide(buf))),
 480             ) {
 481                 return Some(path);
 482             }
 483         }
 484     }
 485
 486     // 5. Parent paths
 487     if let Some(parent_paths) = parent_paths() {
 488         for path in env::split_paths(&parent_paths).filter(|p| !p.as_os_str().is_empty()) {
 489             if let Some(path) = exists(path) {
 490                 return Some(path);
 491             }
 492         }
 493     }
 494     None
 495 }
 496
 497 /// Check if a file exists without following symlinks.
 498 fn program_exists(path: &Path) -> Option<Vec<u16>> {
 499     unsafe {
 500         let path = path::maybe_verbatim(path).ok()?;
 501         // Getting attributes using `GetFileAttributesW` does not follow symlinks
 502         // and it will almost always be successful if the link exists.
 503         // There are some exceptions for special system files (e.g. the pagefile)
 504         // but these are not executable.
 505         if c::GetFileAttributesW(path.as_ptr()) == c::INVALID_FILE_ATTRIBUTES {
 506             None
 507         } else {
 508             Some(path)
 509         }
 510     }
 511 }
 512
 513 impl Stdio {
 514     fn to_handle(&self, stdio_id: c::DWORD, pipe: &mut Option<AnonPipe>) -> io::Result<Handle> {
 515         match *self {
 516             // If no stdio handle is available, then inherit means that it
 517             // should still be unavailable so propagate the
 518             // INVALID_HANDLE_VALUE.
 519             Stdio::Inherit => match stdio::get_handle(stdio_id) {
 520                 Ok(io) => unsafe {
 521                     let io = Handle::from_raw_handle(io);
 522                     let ret = io.duplicate(0, true, c::DUPLICATE_SAME_ACCESS);
 523                     io.into_raw_handle();
 524                     ret
 525                 },
 526                 Err(..) => unsafe { Ok(Handle::from_raw_handle(c::INVALID_HANDLE_VALUE)) },
 527             },
 528
 529             Stdio::MakePipe => {
 530                 let ours_readable = stdio_id != c::STD_INPUT_HANDLE;
 531                 let pipes = pipe::anon_pipe(ours_readable, true)?;
 532                 *pipe = Some(pipes.ours);
 533                 Ok(pipes.theirs.into_handle())
 534             }
 535
 536             Stdio::Pipe(ref source) => {
 537                 let ours_readable = stdio_id != c::STD_INPUT_HANDLE;
 538                 pipe::spawn_pipe_relay(source, ours_readable, true).map(AnonPipe::into_handle)
 539             }
 540
 541             Stdio::Handle(ref handle) => handle.duplicate(0, true, c::DUPLICATE_SAME_ACCESS),
 542
 543             // Open up a reference to NUL with appropriate read/write
 544             // permissions as well as the ability to be inherited to child
 545             // processes (as this is about to be inherited).
 546             Stdio::Null => {
 547                 let size = mem::size_of::<c::SECURITY_ATTRIBUTES>();
 548                 let mut sa = c::SECURITY_ATTRIBUTES {
 549                     nLength: size as c::DWORD,
 550                     lpSecurityDescriptor: ptr::null_mut(),
 551                     bInheritHandle: 1,
 552                 };
 553                 let mut opts = OpenOptions::new();
 554                 opts.read(stdio_id == c::STD_INPUT_HANDLE);
 555                 opts.write(stdio_id != c::STD_INPUT_HANDLE);
 556                 opts.security_attributes(&mut sa);
 557                 File::open(Path::new("NUL"), &opts).map(|file| file.into_inner())
 558             }
 559         }
 560     }
 561 }
 562
 563 impl From<AnonPipe> for Stdio {
 564     fn from(pipe: AnonPipe) -> Stdio {
 565         Stdio::Pipe(pipe)
 566     }
 567 }
 568
 569 impl From<File> for Stdio {
 570     fn from(file: File) -> Stdio {
 571         Stdio::Handle(file.into_inner())
 572     }
 573 }
 574
 575 ////////////////////////////////////////////////////////////////////////////////
 576 // Processes
 577 ////////////////////////////////////////////////////////////////////////////////
 578
 579 /// A value representing a child process.
 580 ///
 581 /// The lifetime of this value is linked to the lifetime of the actual
 582 /// process - the Process destructor calls self.finish() which waits
 583 /// for the process to terminate.
 584 pub struct Process {
 585     handle: Handle,
 586     main_thread_handle: Handle,
 587 }
 588
 589 impl Process {
 590     pub fn kill(&mut self) -> io::Result<()> {
 591         cvt(unsafe { c::TerminateProcess(self.handle.as_raw_handle(), 1) })?;
 592         Ok(())
 593     }
 594
 595     pub fn id(&self) -> u32 {
 596         unsafe { c::GetProcessId(self.handle.as_raw_handle()) as u32 }
 597     }
 598
 599     pub fn main_thread_handle(&self) -> BorrowedHandle<'_> {
 600         self.main_thread_handle.as_handle()
 601     }
 602
 603     pub fn wait(&mut self) -> io::Result<ExitStatus> {
 604         unsafe {
 605             let res = c::WaitForSingleObject(self.handle.as_raw_handle(), c::INFINITE);
 606             if res != c::WAIT_OBJECT_0 {
 607                 return Err(Error::last_os_error());
 608             }
 609             let mut status = 0;
 610             cvt(c::GetExitCodeProcess(self.handle.as_raw_handle(), &mut status))?;
 611             Ok(ExitStatus(status))
 612         }
 613     }
 614
 615     pub fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
 616         unsafe {
 617             match c::WaitForSingleObject(self.handle.as_raw_handle(), 0) {
 618                 c::WAIT_OBJECT_0 => {}
 619                 c::WAIT_TIMEOUT => {
 620                     return Ok(None);
 621                 }
 622                 _ => return Err(io::Error::last_os_error()),
 623             }
 624             let mut status = 0;
 625             cvt(c::GetExitCodeProcess(self.handle.as_raw_handle(), &mut status))?;
 626             Ok(Some(ExitStatus(status)))
 627         }
 628     }
 629
 630     pub fn handle(&self) -> &Handle {
 631         &self.handle
 632     }
 633
 634     pub fn into_handle(self) -> Handle {
 635         self.handle
 636     }
 637 }
 638
 639 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
 640 pub struct ExitStatus(c::DWORD);
 641
 642 impl ExitStatus {
 643     pub fn exit_ok(&self) -> Result<(), ExitStatusError> {
 644         match NonZeroDWORD::try_from(self.0) {
 645             /* was nonzero */ Ok(failure) => Err(ExitStatusError(failure)),
 646             /* was zero, couldn't convert */ Err(_) => Ok(()),
 647         }
 648     }
 649     pub fn code(&self) -> Option<i32> {
 650         Some(self.0 as i32)
 651     }
 652 }
 653
 654 /// Converts a raw `c::DWORD` to a type-safe `ExitStatus` by wrapping it without copying.
 655 impl From<c::DWORD> for ExitStatus {
 656     fn from(u: c::DWORD) -> ExitStatus {
 657         ExitStatus(u)
 658     }
 659 }
 660
 661 impl fmt::Display for ExitStatus {
 662     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 663         // Windows exit codes with the high bit set typically mean some form of
 664         // unhandled exception or warning. In this scenario printing the exit
 665         // code in decimal doesn't always make sense because it's a very large
 666         // and somewhat gibberish number. The hex code is a bit more
 667         // recognizable and easier to search for, so print that.
 668         if self.0 & 0x80000000 != 0 {
 669             write!(f, "exit code: {:#x}", self.0)
 670         } else {
 671             write!(f, "exit code: {}", self.0)
 672         }
 673     }
 674 }
 675
 676 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
 677 pub struct ExitStatusError(c::NonZeroDWORD);
 678
 679 impl Into<ExitStatus> for ExitStatusError {
 680     fn into(self) -> ExitStatus {
 681         ExitStatus(self.0.into())
 682     }
 683 }
 684
 685 impl ExitStatusError {
 686     pub fn code(self) -> Option<NonZeroI32> {
 687         Some((u32::from(self.0) as i32).try_into().unwrap())
 688     }
 689 }
 690
 691 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
 692 pub struct ExitCode(c::DWORD);
 693
 694 impl ExitCode {
 695     pub const SUCCESS: ExitCode = ExitCode(EXIT_SUCCESS as _);
 696     pub const FAILURE: ExitCode = ExitCode(EXIT_FAILURE as _);
 697
 698     #[inline]
 699     pub fn as_i32(&self) -> i32 {
 700         self.0 as i32
 701     }
 702 }
 703
 704 impl From<u8> for ExitCode {
 705     fn from(code: u8) -> Self {
 706         ExitCode(c::DWORD::from(code))
 707     }
 708 }
 709
 710 impl From<u32> for ExitCode {
 711     fn from(code: u32) -> Self {
 712         ExitCode(c::DWORD::from(code))
 713     }
 714 }
 715
 716 fn zeroed_startupinfo() -> c::STARTUPINFO {
 717     c::STARTUPINFO {
 718         cb: 0,
 719         lpReserved: ptr::null_mut(),
 720         lpDesktop: ptr::null_mut(),
 721         lpTitle: ptr::null_mut(),
 722         dwX: 0,
 723         dwY: 0,
 724         dwXSize: 0,
 725         dwYSize: 0,
 726         dwXCountChars: 0,
 727         dwYCountCharts: 0,
 728         dwFillAttribute: 0,
 729         dwFlags: 0,
 730         wShowWindow: 0,
 731         cbReserved2: 0,
 732         lpReserved2: ptr::null_mut(),
 733         hStdInput: c::INVALID_HANDLE_VALUE,
 734         hStdOutput: c::INVALID_HANDLE_VALUE,
 735         hStdError: c::INVALID_HANDLE_VALUE,
 736     }
 737 }
 738
 739 fn zeroed_process_information() -> c::PROCESS_INFORMATION {
 740     c::PROCESS_INFORMATION {
 741         hProcess: ptr::null_mut(),
 742         hThread: ptr::null_mut(),
 743         dwProcessId: 0,
 744         dwThreadId: 0,
 745     }
 746 }
 747
 748 // Produces a wide string *without terminating null*; returns an error if
 749 // `prog` or any of the `args` contain a nul.
 750 fn make_command_line(argv0: &OsStr, args: &[Arg], force_quotes: bool) -> io::Result<Vec<u16>> {
 751     // Encode the command and arguments in a command line string such
 752     // that the spawned process may recover them using CommandLineToArgvW.
 753     let mut cmd: Vec<u16> = Vec::new();
 754
 755     // Always quote the program name so CreateProcess to avoid ambiguity when
 756     // the child process parses its arguments.
 757     // Note that quotes aren't escaped here because they can't be used in arg0.
 758     // But that's ok because file paths can't contain quotes.
 759     cmd.push(b'"' as u16);
 760     cmd.extend(argv0.encode_wide());
 761     cmd.push(b'"' as u16);
 762
 763     for arg in args {
 764         cmd.push(' ' as u16);
 765         args::append_arg(&mut cmd, arg, force_quotes)?;
 766     }
 767     Ok(cmd)
 768 }
 769
 770 // Get `cmd.exe` for use with bat scripts, encoded as a UTF-16 string.
 771 fn command_prompt() -> io::Result<Vec<u16>> {
 772     let mut system: Vec<u16> = super::fill_utf16_buf(
 773         |buf, size| unsafe { c::GetSystemDirectoryW(buf, size) },
 774         |buf| buf.into(),
 775     )?;
 776     system.extend("\\cmd.exe".encode_utf16().chain([0]));
 777     Ok(system)
 778 }
 779
 780 fn make_envp(maybe_env: Option<BTreeMap<EnvKey, OsString>>) -> io::Result<(*mut c_void, Vec<u16>)> {
 781     // On Windows we pass an "environment block" which is not a char**, but
 782     // rather a concatenation of null-terminated k=v\0 sequences, with a final
 783     // \0 to terminate.
 784     if let Some(env) = maybe_env {
 785         let mut blk = Vec::new();
 786
 787         // If there are no environment variables to set then signal this by
 788         // pushing a null.
 789         if env.is_empty() {
 790             blk.push(0);
 791         }
 792
 793         for (k, v) in env {
 794             ensure_no_nuls(k.os_string)?;
 795             blk.extend(k.utf16);
 796             blk.push('=' as u16);
 797             blk.extend(ensure_no_nuls(v)?.encode_wide());
 798             blk.push(0);
 799         }
 800         blk.push(0);
 801         Ok((blk.as_mut_ptr() as *mut c_void, blk))
 802     } else {
 803         Ok((ptr::null_mut(), Vec::new()))
 804     }
 805 }
 806
 807 fn make_dirp(d: Option<&OsString>) -> io::Result<(*const u16, Vec<u16>)> {
 808     match d {
 809         Some(dir) => {
 810             let mut dir_str: Vec<u16> = ensure_no_nuls(dir)?.encode_wide().collect();
 811             dir_str.push(0);
 812             Ok((dir_str.as_ptr(), dir_str))
 813         }
 814         None => Ok((ptr::null(), Vec::new())),
 815     }
 816 }
 817
 818 pub struct CommandArgs<'a> {
 819     iter: crate::slice::Iter<'a, Arg>,
 820 }
 821
 822 impl<'a> Iterator for CommandArgs<'a> {
 823     type Item = &'a OsStr;
 824     fn next(&mut self) -> Option<&'a OsStr> {
 825         self.iter.next().map(|arg| match arg {
 826             Arg::Regular(s) | Arg::Raw(s) => s.as_ref(),
 827         })
 828     }
 829     fn size_hint(&self) -> (usize, Option<usize>) {
 830         self.iter.size_hint()
 831     }
 832 }
 833
 834 impl<'a> ExactSizeIterator for CommandArgs<'a> {
 835     fn len(&self) -> usize {
 836         self.iter.len()
 837     }
 838     fn is_empty(&self) -> bool {
 839         self.iter.is_empty()
 840     }
 841 }
 842
 843 impl<'a> fmt::Debug for CommandArgs<'a> {
 844     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 845         f.debug_list().entries(self.iter.clone()).finish()
 846     }
 847 }