std: Ensure fs::{DirEntry, ReadDir} are Send/Sync

The windows/unix modules were currently inconsistent about the traits being
implemented for `DirEntry` and there isn't much particular reason why the traits
*couldn't* be implemented for `ReadDir` and `DirEntry`, so this commit ensures
that they are implemented.

Closes #22577

Author: alexcrichton

src/libstd/sys/unix/fs2.rs

@@ -18,7 +18,7 @@ use libc::{self, c_int, c_void, size_t, off_t, c_char, mode_t};
 use mem;
 use path::{Path, PathBuf};
 use ptr;
-use rc::Rc;
+use sync::Arc;
 use sys::fd::FileDesc;
 use sys::{c, cvt, cvt_r};
 use sys_common::FromInner;
@@ -31,14 +31,18 @@ pub struct FileAttr {
 }
 
 pub struct ReadDir {
-    dirp: *mut libc::DIR,
-    root: Rc<PathBuf>,
+    dirp: Dir,
+    root: Arc<PathBuf>,
 }
 
+struct Dir(*mut libc::DIR);
+
+unsafe impl Send for Dir {}
+unsafe impl Sync for Dir {}
+
 pub struct DirEntry {
-    buf: Vec<u8>,
-    dirent: *mut libc::dirent_t,
-    root: Rc<PathBuf>,
+    buf: Vec<u8>, // actually *mut libc::dirent_t
+    root: Arc<PathBuf>,
 }
 
 #[derive(Clone)]
@@ -109,7 +113,7 @@ impl Iterator for ReadDir {
 
         let mut entry_ptr = ptr::null_mut();
         loop {
-            if unsafe { libc::readdir_r(self.dirp, ptr, &mut entry_ptr) != 0 } {
+            if unsafe { libc::readdir_r(self.dirp.0, ptr, &mut entry_ptr) != 0 } {
                 return Some(Err(Error::last_os_error()))
             }
             if entry_ptr.is_null() {
@@ -118,7 +122,6 @@ impl Iterator for ReadDir {
 
             let entry = DirEntry {
                 buf: buf,
-                dirent: entry_ptr,
                 root: self.root.clone()
             };
             if entry.name_bytes() == b"." || entry.name_bytes() == b".." {
@@ -130,9 +133,9 @@ impl Iterator for ReadDir {
     }
 }
 
-impl Drop for ReadDir {
+impl Drop for Dir {
     fn drop(&mut self) {
-        let r = unsafe { libc::closedir(self.dirp) };
+        let r = unsafe { libc::closedir(self.0) };
         debug_assert_eq!(r, 0);
     }
 }
@@ -147,9 +150,13 @@ impl DirEntry {
             fn rust_list_dir_val(ptr: *mut libc::dirent_t) -> *const c_char;
         }
         unsafe {
-            CStr::from_ptr(rust_list_dir_val(self.dirent)).to_bytes()
+            CStr::from_ptr(rust_list_dir_val(self.dirent())).to_bytes()
         }
     }
+
+    fn dirent(&self) -> *mut libc::dirent_t {
+        self.buf.as_ptr() as *mut _
+    }
 }
 
 impl OpenOptions {
@@ -279,14 +286,14 @@ pub fn mkdir(p: &Path) -> io::Result<()> {
 }
 
 pub fn readdir(p: &Path) -> io::Result<ReadDir> {
-    let root = Rc::new(p.to_path_buf());
+    let root = Arc::new(p.to_path_buf());
     let p = try!(cstr(p));
     unsafe {
         let ptr = libc::opendir(p.as_ptr());
         if ptr.is_null() {
             Err(Error::last_os_error())
         } else {
-            Ok(ReadDir { dirp: ptr, root: root })
+            Ok(ReadDir { dirp: Dir(ptr), root: root })
         }
     }
 }

src/libstd/sys/windows/fs2.rs

@@ -19,6 +19,7 @@ use libc::{self, HANDLE};
 use mem;
 use path::{Path, PathBuf};
 use ptr;
+use sync::Arc;
 use sys::handle::Handle as RawHandle;
 use sys::{c, cvt};
 use vec::Vec;
@@ -27,12 +28,20 @@ pub struct File { handle: RawHandle }
 pub struct FileAttr { data: c::WIN32_FILE_ATTRIBUTE_DATA }
 
 pub struct ReadDir {
-    handle: libc::HANDLE,
-    root: PathBuf,
+    handle: FindNextFileHandle,
+    root: Arc<PathBuf>,
     first: Option<libc::WIN32_FIND_DATAW>,
 }
 
-pub struct DirEntry { path: PathBuf }
+struct FindNextFileHandle(libc::HANDLE);
+
+unsafe impl Send for FindNextFileHandle {}
+unsafe impl Sync for FindNextFileHandle {}
+
+pub struct DirEntry {
+    root: Arc<PathBuf>,
+    data: libc::WIN32_FIND_DATAW,
+}
 
 #[derive(Clone, Default)]
 pub struct OpenOptions {
@@ -61,7 +70,7 @@ impl Iterator for ReadDir {
         unsafe {
             let mut wfd = mem::zeroed();
             loop {
-                if libc::FindNextFileW(self.handle, &mut wfd) == 0 {
+                if libc::FindNextFileW(self.handle.0, &mut wfd) == 0 {
                     if libc::GetLastError() ==
                         c::ERROR_NO_MORE_FILES as libc::DWORD {
                         return None
@@ -77,29 +86,31 @@ impl Iterator for ReadDir {
     }
 }
 
-impl Drop for ReadDir {
+impl Drop for FindNextFileHandle {
     fn drop(&mut self) {
-        let r = unsafe { libc::FindClose(self.handle) };
+        let r = unsafe { libc::FindClose(self.0) };
         debug_assert!(r != 0);
     }
 }
 
 impl DirEntry {
-    fn new(root: &Path, wfd: &libc::WIN32_FIND_DATAW) -> Option<DirEntry> {
+    fn new(root: &Arc<PathBuf>, wfd: &libc::WIN32_FIND_DATAW) -> Option<DirEntry> {
         match &wfd.cFileName[0..3] {
             // check for '.' and '..'
             [46, 0, ..] |
             [46, 46, 0, ..] => return None,
             _ => {}
         }
 
-        let filename = super::truncate_utf16_at_nul(&wfd.cFileName);
-        let filename: OsString = OsStringExt::from_wide(filename);
-        Some(DirEntry { path: root.join(&filename) })
+        Some(DirEntry {
+            root: root.clone(),
+            data: *wfd,
+        })
     }
 
     pub fn path(&self) -> PathBuf {
-        self.path.clone()
+        let filename = super::truncate_utf16_at_nul(&self.data.cFileName);
+        self.root.join(&<OsString as OsStringExt>::from_wide(filename))
     }
 }
 
@@ -312,7 +323,11 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
         let mut wfd = mem::zeroed();
         let find_handle = libc::FindFirstFileW(path.as_ptr(), &mut wfd);
         if find_handle != libc::INVALID_HANDLE_VALUE {
-            Ok(ReadDir { handle: find_handle, root: root, first: Some(wfd) })
+            Ok(ReadDir {
+                handle: FindNextFileHandle(find_handle),
+                root: Arc::new(root),
+                first: Some(wfd),
+            })
         } else {
             Err(Error::last_os_error())
         }

src/test/run-pass/issue-22577.rs

@@ -0,0 +1,29 @@
+// Copyright 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 std::{fs, net};
+
+fn assert_both<T: Send + Sync>() {}
+
+fn main() {
+    assert_both::<fs::File>();
+    assert_both::<fs::Metadata>();
+    assert_both::<fs::ReadDir>();
+    assert_both::<fs::DirEntry>();
+    assert_both::<fs::WalkDir>();
+    assert_both::<fs::OpenOptions>();
+    assert_both::<fs::Permissions>();
+
+    assert_both::<net::TcpStream>();
+    assert_both::<net::TcpListener>();
+    assert_both::<net::UdpSocket>();
+    assert_both::<net::SocketAddr>();
+    assert_both::<net::IpAddr>();
+}