Retain suid/sgid/sticky bits in Metadata.permissions

src/libstd/fs.rs

@@ -2160,6 +2160,27 @@ mod tests {
         check!(fs::remove_file(&filename));
     }
 
+    #[test]
+    #[cfg(unix)]
+    fn set_get_unix_permissions() {
+        use os::unix::fs::PermissionsExt;
+
+        let tmpdir = tmpdir();
+        let filename = &tmpdir.join("set_get_unix_permissions");
+        check!(fs::create_dir(filename));
+        let mask = 0o7777;
+
+        check!(fs::set_permissions(filename,
+                                   fs::Permissions::from_mode(0)));
+        let metadata0 = check!(fs::metadata(filename));
+        assert_eq!(mask & metadata0.permissions().mode(), 0);
+
+        check!(fs::set_permissions(filename,
+                                   fs::Permissions::from_mode(0o1777)));
+        let metadata1 = check!(fs::metadata(filename));
+        assert_eq!(mask & metadata1.permissions().mode(), 0o1777);
+    }
+
     #[test]
     #[cfg(windows)]
     fn file_test_io_seek_read_write() {

src/libstd/sys/unix/ext/fs.rs

@@ -68,8 +68,8 @@ impl FileExt for fs::File {
 /// Unix-specific extensions to `Permissions`
 #[stable(feature = "fs_ext", since = "1.1.0")]
 pub trait PermissionsExt {
-    /// Returns the underlying raw `mode_t` bits that are the standard Unix
-    /// permissions for this file.
+    /// Returns the underlying raw `st_mode` bits that contain the standard
+    /// Unix permissions for this file.
     ///
     /// # Examples
     ///

src/libstd/sys/unix/fs.rs

@@ -95,7 +95,7 @@ pub struct DirBuilder { mode: mode_t }
 impl FileAttr {
     pub fn size(&self) -> u64 { self.stat.st_size as u64 }
     pub fn perm(&self) -> FilePermissions {
-        FilePermissions { mode: (self.stat.st_mode as mode_t) & 0o777 }
+        FilePermissions { mode: (self.stat.st_mode as mode_t) }
     }
 
     pub fn file_type(&self) -> FileType {