std: Refactor process spawning on Unix
* Build up the argp/envp pointers while the `Command` is being constructed rather than only when `spawn` is called. This will allow better sharing of code between fork/exec paths. * Rename `child_after_fork` to `exec` and have it only perform the exec half of the spawning. This also means the return type has changed to `io::Error` rather than `!` to represent errors that happen.
This commit is contained in:
parent
096dbf84c7
commit
6c41984690
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@ -209,7 +209,9 @@ impl Command {
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/// Add multiple arguments to pass to the program.
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#[stable(feature = "process", since = "1.0.0")]
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pub fn args<S: AsRef<OsStr>>(&mut self, args: &[S]) -> &mut Command {
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self.inner.args(args.iter().map(AsRef::as_ref));
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for arg in args {
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self.arg(arg.as_ref());
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}
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self
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}
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@ -12,8 +12,8 @@
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#![stable(feature = "rust1", since = "1.0.0")]
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use os::unix::raw::{uid_t, gid_t};
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use os::unix::io::{FromRawFd, RawFd, AsRawFd, IntoRawFd};
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use os::unix::raw::{uid_t, gid_t};
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use process;
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use sys;
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use sys_common::{AsInnerMut, AsInner, FromInner, IntoInner};
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@ -13,27 +13,46 @@
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use prelude::v1::*;
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use os::unix::prelude::*;
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use collections::HashMap;
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use collections::hash_map::{HashMap, Entry};
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use env;
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use ffi::{OsString, OsStr, CString, CStr};
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use fmt;
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use io::{self, Error, ErrorKind};
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use libc::{self, pid_t, c_void, c_int, gid_t, uid_t};
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use libc::{self, pid_t, c_int, gid_t, uid_t, c_char};
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use mem;
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use ptr;
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use sys::fd::FileDesc;
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use sys::fs::{File, OpenOptions};
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use sys::pipe::AnonPipe;
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use sys::{self, cvt, cvt_r};
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////////////////////////////////////////////////////////////////////////////////
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// Command
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////////////////////////////////////////////////////////////////////////////////
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#[derive(Clone)]
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pub struct Command {
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// Currently we try hard to ensure that the call to `.exec()` doesn't
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// actually allocate any memory. While many platforms try to ensure that
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// memory allocation works after a fork in a multithreaded process, it's
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// been observed to be buggy and somewhat unreliable, so we do our best to
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// just not do it at all!
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//
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// Along those lines, the `argv` and `envp` raw pointers here are exactly
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// what's gonna get passed to `execvp`. The `argv` array starts with the
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// `program` and ends with a NULL, and the `envp` pointer, if present, is
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// also null-terminated.
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//
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// Right now we don't support removing arguments, so there's no much fancy
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// support there, but we support adding and removing environment variables,
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// so a side table is used to track where in the `envp` array each key is
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// located. Whenever we add a key we update it in place if it's already
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// present, and whenever we remove a key we update the locations of all
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// other keys.
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program: CString,
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args: Vec<CString>,
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env: Option<HashMap<OsString, OsString>>, // Guaranteed to have no NULs.
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env: Option<HashMap<OsString, (usize, CString)>>,
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argv: Vec<*const c_char>,
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envp: Option<Vec<*const c_char>>,
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cwd: Option<CString>,
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uid: Option<uid_t>,
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gid: Option<gid_t>,
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@ -44,10 +63,13 @@ pub struct Command {
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impl Command {
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pub fn new(program: &OsStr) -> Command {
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let mut saw_nul = false;
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let program = os2c(program, &mut saw_nul);
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Command {
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program: os2c(program, &mut saw_nul),
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argv: vec![program.as_ptr(), 0 as *const _],
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program: program,
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args: Vec::new(),
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env: None,
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envp: None,
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cwd: None,
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uid: None,
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gid: None,
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@ -57,40 +79,79 @@ impl Command {
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}
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pub fn arg(&mut self, arg: &OsStr) {
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self.args.push(os2c(arg, &mut self.saw_nul));
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// Overwrite the trailing NULL pointer in `argv` and then add a new null
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// pointer.
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let arg = os2c(arg, &mut self.saw_nul);
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self.argv[self.args.len() + 1] = arg.as_ptr();
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self.argv.push(0 as *const _);
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// Also make sure we keep track of the owned value to schedule a
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// destructor for this memory.
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self.args.push(arg);
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}
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pub fn args<'a, I: Iterator<Item = &'a OsStr>>(&mut self, args: I) {
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let mut saw_nul = self.saw_nul;
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self.args.extend(args.map(|arg| os2c(arg, &mut saw_nul)));
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self.saw_nul = saw_nul;
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}
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fn init_env_map(&mut self) {
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fn init_env_map(&mut self) -> (&mut HashMap<OsString, (usize, CString)>,
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&mut Vec<*const c_char>) {
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if self.env.is_none() {
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// Will not add NULs to env: preexisting environment will not contain any.
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self.env = Some(env::vars_os().collect());
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let mut map = HashMap::new();
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let mut envp = Vec::new();
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for (k, v) in env::vars_os() {
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let s = pair_to_key(&k, &v, &mut self.saw_nul);
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envp.push(s.as_ptr());
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map.insert(k, (envp.len() - 1, s));
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}
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envp.push(0 as *const _);
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self.env = Some(map);
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self.envp = Some(envp);
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}
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(self.env.as_mut().unwrap(), self.envp.as_mut().unwrap())
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}
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pub fn env(&mut self, key: &OsStr, val: &OsStr) {
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let k = OsString::from_vec(os2c(key, &mut self.saw_nul).into_bytes());
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let v = OsString::from_vec(os2c(val, &mut self.saw_nul).into_bytes());
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let new_key = pair_to_key(key, val, &mut self.saw_nul);
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let (map, envp) = self.init_env_map();
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// Will not add NULs to env: return without inserting if any were seen.
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if self.saw_nul {
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return;
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// If `key` is already present then we we just update `envp` in place
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// (and store the owned value), but if it's not there we override the
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// trailing NULL pointer, add a new NULL pointer, and store where we
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// were located.
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match map.entry(key.to_owned()) {
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Entry::Occupied(mut e) => {
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let (i, ref mut s) = *e.get_mut();
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envp[i] = new_key.as_ptr();
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*s = new_key;
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}
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Entry::Vacant(e) => {
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let len = envp.len();
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envp[len - 1] = new_key.as_ptr();
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envp.push(0 as *const _);
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e.insert((len - 1, new_key));
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}
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}
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}
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self.init_env_map();
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self.env.as_mut()
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.unwrap()
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.insert(k, v);
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}
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pub fn env_remove(&mut self, key: &OsStr) {
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self.init_env_map();
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self.env.as_mut().unwrap().remove(key);
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let (map, envp) = self.init_env_map();
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// If we actually ended up removing a key, then we need to update the
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// position of all keys that come after us in `envp` because they're all
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// one element sooner now.
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if let Some((i, _)) = map.remove(key) {
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envp.remove(i);
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for (_, &mut (ref mut j, _)) in map.iter_mut() {
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if *j >= i {
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*j -= 1;
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}
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}
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}
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}
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pub fn env_clear(&mut self) {
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self.env = Some(HashMap::new())
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self.env = Some(HashMap::new());
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self.envp = Some(vec![0 as *const _]);
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}
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pub fn cwd(&mut self, dir: &OsStr) {
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self.cwd = Some(os2c(dir, &mut self.saw_nul));
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}
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@ -112,6 +173,18 @@ fn os2c(s: &OsStr, saw_nul: &mut bool) -> CString {
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})
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}
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fn pair_to_key(key: &OsStr, value: &OsStr, saw_nul: &mut bool) -> CString {
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let (key, value) = (key.as_bytes(), value.as_bytes());
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let mut v = Vec::with_capacity(key.len() + value.len() + 1);
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v.extend(key);
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v.push(b'=');
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v.extend(value);
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CString::new(v).unwrap_or_else(|_e| {
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*saw_nul = true;
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CString::new("foo=bar").unwrap()
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})
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}
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impl fmt::Debug for Command {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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try!(write!(f, "{:?}", self.program));
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return Err(io::Error::new(ErrorKind::InvalidInput, "nul byte found in provided data"));
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}
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let dirp = cfg.cwd.as_ref().map(|c| c.as_ptr()).unwrap_or(ptr::null());
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let (envp, _a, _b) = make_envp(cfg.env.as_ref());
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let (argv, _a) = make_argv(&cfg.program, &cfg.args);
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let (input, output) = try!(sys::pipe::anon_pipe());
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let pid = unsafe {
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match libc::fork() {
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match try!(cvt(libc::fork())) {
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0 => {
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drop(input);
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Process::child_after_fork(cfg, output, argv, envp, dirp,
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in_fd, out_fd, err_fd)
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let err = Process::exec(cfg, in_fd, out_fd, err_fd);
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let errno = err.raw_os_error().unwrap_or(libc::EINVAL) as u32;
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let bytes = [
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(errno >> 24) as u8,
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(errno >> 16) as u8,
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(errno >> 8) as u8,
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(errno >> 0) as u8,
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CLOEXEC_MSG_FOOTER[0], CLOEXEC_MSG_FOOTER[1],
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CLOEXEC_MSG_FOOTER[2], CLOEXEC_MSG_FOOTER[3]
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];
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// pipe I/O up to PIPE_BUF bytes should be atomic, and then
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// we want to be sure we *don't* run at_exit destructors as
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// we're being torn down regardless
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assert!(output.write(&bytes).is_ok());
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libc::_exit(1)
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}
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n if n < 0 => return Err(Error::last_os_error()),
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n => n,
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}
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};
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// allocation). Instead we just close it manually. This will never
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// have the drop glue anyway because this code never returns (the
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// child will either exec() or invoke libc::exit)
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unsafe fn child_after_fork(cfg: &Command,
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mut output: AnonPipe,
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argv: *const *const libc::c_char,
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envp: *const libc::c_void,
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dirp: *const libc::c_char,
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in_fd: Stdio,
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out_fd: Stdio,
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err_fd: Stdio) -> ! {
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fn fail(output: &mut AnonPipe) -> ! {
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let errno = sys::os::errno() as u32;
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let bytes = [
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(errno >> 24) as u8,
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(errno >> 16) as u8,
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(errno >> 8) as u8,
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(errno >> 0) as u8,
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CLOEXEC_MSG_FOOTER[0], CLOEXEC_MSG_FOOTER[1],
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CLOEXEC_MSG_FOOTER[2], CLOEXEC_MSG_FOOTER[3]
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];
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// pipe I/O up to PIPE_BUF bytes should be atomic, and then we want
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// to be sure we *don't* run at_exit destructors as we're being torn
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// down regardless
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assert!(output.write(&bytes).is_ok());
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unsafe { libc::_exit(1) }
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unsafe fn exec(cfg: &Command,
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in_fd: Stdio,
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out_fd: Stdio,
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err_fd: Stdio) -> io::Error {
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macro_rules! try {
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($e:expr) => (match $e {
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Ok(e) => e,
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Err(e) => return e,
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})
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}
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// Make sure that the source descriptors are not an stdio descriptor,
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// suppose we want the child's stderr to be the parent's stdout, and
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// the child's stdout to be the parent's stderr. No matter which we
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// dup first, the second will get overwritten prematurely.
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let maybe_migrate = |src: Stdio, output: &mut AnonPipe| {
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let maybe_migrate = |src: Stdio| {
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match src {
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Stdio::Raw(fd @ libc::STDIN_FILENO) |
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Stdio::Raw(fd @ libc::STDOUT_FILENO) |
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Stdio::Raw(fd @ libc::STDERR_FILENO) => {
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let fd = match cvt_r(|| libc::dup(fd)) {
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Ok(fd) => fd,
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Err(_) => fail(output),
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};
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let fd = FileDesc::new(fd);
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fd.set_cloexec();
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Stdio::Raw(fd.into_raw())
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},
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cvt_r(|| libc::dup(fd)).map(|fd| {
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let fd = FileDesc::new(fd);
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fd.set_cloexec();
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Stdio::Raw(fd.into_raw())
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})
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}
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s @ Stdio::None |
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s @ Stdio::Inherit |
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s @ Stdio::Raw(_) => s,
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s @ Stdio::Raw(_) => Ok(s),
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}
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};
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let in_fd = try!(maybe_migrate(in_fd));
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let out_fd = try!(maybe_migrate(out_fd));
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let err_fd = try!(maybe_migrate(err_fd));
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let setup = |src: Stdio, dst: c_int| {
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match src {
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Stdio::Inherit => true,
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Stdio::Raw(fd) => cvt_r(|| libc::dup2(fd, dst)).is_ok(),
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Stdio::Inherit => Ok(()),
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Stdio::Raw(fd) => cvt_r(|| libc::dup2(fd, dst)).map(|_| ()),
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// If a stdio file descriptor is set to be ignored, we open up
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// /dev/null into that file descriptor. Otherwise, the first
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@ -373,29 +440,18 @@ impl Process {
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opts.write(dst != libc::STDIN_FILENO);
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let devnull = CStr::from_ptr(b"/dev/null\0".as_ptr()
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as *const _);
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if let Ok(f) = File::open_c(devnull, &opts) {
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cvt_r(|| libc::dup2(f.fd().raw(), dst)).is_ok()
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} else {
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false
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}
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File::open_c(devnull, &opts).and_then(|f| {
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cvt_r(|| libc::dup2(f.fd().raw(), dst)).map(|_| ())
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})
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}
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}
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};
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// Make sure we migrate all source descriptors before
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// we start overwriting them
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let in_fd = maybe_migrate(in_fd, &mut output);
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let out_fd = maybe_migrate(out_fd, &mut output);
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let err_fd = maybe_migrate(err_fd, &mut output);
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if !setup(in_fd, libc::STDIN_FILENO) { fail(&mut output) }
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if !setup(out_fd, libc::STDOUT_FILENO) { fail(&mut output) }
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if !setup(err_fd, libc::STDERR_FILENO) { fail(&mut output) }
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try!(setup(in_fd, libc::STDIN_FILENO));
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try!(setup(out_fd, libc::STDOUT_FILENO));
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try!(setup(err_fd, libc::STDERR_FILENO));
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if let Some(u) = cfg.gid {
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if libc::setgid(u as libc::gid_t) != 0 {
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fail(&mut output);
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}
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try!(cvt(libc::setgid(u as gid_t)));
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}
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if let Some(u) = cfg.uid {
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// When dropping privileges from root, the `setgroups` call
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|
@ -407,9 +463,7 @@ impl Process {
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// privilege dropping function.
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let _ = libc::setgroups(0, ptr::null());
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if libc::setuid(u as libc::uid_t) != 0 {
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fail(&mut output);
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}
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try!(cvt(libc::setuid(u as uid_t)));
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}
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if cfg.session_leader {
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// Don't check the error of setsid because it fails if we're the
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|
@ -417,16 +471,15 @@ impl Process {
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// error, but ignore it anyway.
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let _ = libc::setsid();
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}
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if !dirp.is_null() && libc::chdir(dirp) == -1 {
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fail(&mut output);
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if let Some(ref cwd) = cfg.cwd {
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try!(cvt(libc::chdir(cwd.as_ptr())));
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}
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if !envp.is_null() {
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*sys::os::environ() = envp as *const _;
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if let Some(ref envp) = cfg.envp {
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*sys::os::environ() = envp.as_ptr();
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}
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#[cfg(not(target_os = "nacl"))]
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unsafe fn reset_signal_handling(output: &mut AnonPipe) {
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use mem;
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// NaCl has no signal support.
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if cfg!(not(target_os = "nacl")) {
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// Reset signal handling so the child process starts in a
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// standardized state. libstd ignores SIGPIPE, and signal-handling
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// libraries often set a mask. Child processes inherit ignored
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|
@ -435,23 +488,17 @@ impl Process {
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// need to clean things up now to avoid confusing the program
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// we're about to run.
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let mut set: libc::sigset_t = mem::uninitialized();
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if libc::sigemptyset(&mut set) != 0 ||
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libc::pthread_sigmask(libc::SIG_SETMASK, &set, ptr::null_mut()) != 0 ||
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libc::signal(
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libc::SIGPIPE, mem::transmute(libc::SIG_DFL)
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) == mem::transmute(libc::SIG_ERR)
|
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{
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fail(output);
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try!(cvt(libc::sigemptyset(&mut set)));
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try!(cvt(libc::pthread_sigmask(libc::SIG_SETMASK, &set,
|
||||
ptr::null_mut())));
|
||||
let ret = libc::signal(libc::SIGPIPE, libc::SIG_DFL);
|
||||
if ret == libc::SIG_ERR {
|
||||
return io::Error::last_os_error()
|
||||
}
|
||||
}
|
||||
#[cfg(target_os = "nacl")]
|
||||
unsafe fn reset_signal_handling(_output: &mut AnonPipe) {
|
||||
// NaCl has no signal support.
|
||||
}
|
||||
reset_signal_handling(&mut output);
|
||||
|
||||
let _ = libc::execvp(*argv, argv);
|
||||
fail(&mut output)
|
||||
libc::execvp(cfg.argv[0], cfg.argv.as_ptr());
|
||||
io::Error::last_os_error()
|
||||
}
|
||||
|
||||
pub fn id(&self) -> u32 {
|
||||
|
@ -477,54 +524,6 @@ impl Process {
|
|||
}
|
||||
}
|
||||
|
||||
fn make_argv(prog: &CString, args: &[CString])
|
||||
-> (*const *const libc::c_char, Vec<*const libc::c_char>)
|
||||
{
|
||||
let mut ptrs: Vec<*const libc::c_char> = Vec::with_capacity(args.len()+1);
|
||||
|
||||
// Convert the CStrings into an array of pointers. Also return the
|
||||
// vector that owns the raw pointers, to ensure they live long
|
||||
// enough.
|
||||
ptrs.push(prog.as_ptr());
|
||||
ptrs.extend(args.iter().map(|tmp| tmp.as_ptr()));
|
||||
|
||||
// Add a terminating null pointer (required by libc).
|
||||
ptrs.push(ptr::null());
|
||||
|
||||
(ptrs.as_ptr(), ptrs)
|
||||
}
|
||||
|
||||
fn make_envp(env: Option<&HashMap<OsString, OsString>>)
|
||||
-> (*const c_void, Vec<Vec<u8>>, Vec<*const libc::c_char>)
|
||||
{
|
||||
// On posixy systems we can pass a char** for envp, which is a
|
||||
// null-terminated array of "k=v\0" strings. As with make_argv, we
|
||||
// return two vectors that own the data to ensure that they live
|
||||
// long enough.
|
||||
if let Some(env) = env {
|
||||
let mut tmps = Vec::with_capacity(env.len());
|
||||
|
||||
for pair in env {
|
||||
let mut kv = Vec::new();
|
||||
kv.extend_from_slice(pair.0.as_bytes());
|
||||
kv.push('=' as u8);
|
||||
kv.extend_from_slice(pair.1.as_bytes());
|
||||
kv.push(0); // terminating null
|
||||
tmps.push(kv);
|
||||
}
|
||||
|
||||
let mut ptrs: Vec<*const libc::c_char> =
|
||||
tmps.iter()
|
||||
.map(|tmp| tmp.as_ptr() as *const libc::c_char)
|
||||
.collect();
|
||||
ptrs.push(ptr::null());
|
||||
|
||||
(ptrs.as_ptr() as *const _, tmps, ptrs)
|
||||
} else {
|
||||
(ptr::null(), Vec::new(), Vec::new())
|
||||
}
|
||||
}
|
||||
|
||||
#[cfg(test)]
|
||||
mod tests {
|
||||
use super::*;
|
||||
|
|
|
@ -74,9 +74,6 @@ impl Command {
|
|||
pub fn arg(&mut self, arg: &OsStr) {
|
||||
self.args.push(arg.to_os_string())
|
||||
}
|
||||
pub fn args<'a, I: Iterator<Item = &'a OsStr>>(&mut self, args: I) {
|
||||
self.args.extend(args.map(OsStr::to_os_string))
|
||||
}
|
||||
fn init_env_map(&mut self){
|
||||
if self.env.is_none() {
|
||||
self.env = Some(env::vars_os().map(|(key, val)| {
|
||||
|
|
Loading…
Reference in New Issue