Fix another UB in raw dir

src/fs/raw_dir.rs

@@ -45,7 +45,8 @@ impl<'buf, Fd: AsFd> RawDir<'buf, Fd> {
     /// let fd = openat(cwd(), ".", OFlags::RDONLY | OFlags::DIRECTORY, Mode::empty()).unwrap();
     ///
     /// let mut buf = Vec::with_capacity(8192);
-    /// for entry in RawDir::new(fd, buf.spare_capacity_mut()) {
+    /// let mut iter = RawDir::new(fd, buf.spare_capacity_mut());
+    /// while let Some(entry) = iter.next() {
     ///     let entry = entry.unwrap();
     ///     dbg!(&entry);
     /// }
@@ -60,7 +61,8 @@ impl<'buf, Fd: AsFd> RawDir<'buf, Fd> {
     /// let fd = openat(cwd(), ".", OFlags::RDONLY | OFlags::DIRECTORY, Mode::empty()).unwrap();
     ///
     /// let mut buf = [MaybeUninit::uninit(); 2048];
-    /// for entry in RawDir::new(fd, &mut buf) {
+    /// let mut iter = RawDir::new(fd, &mut buf);
+    /// while let Some(entry) = iter.next() {
     ///     let entry = entry.unwrap();
     ///     dbg!(&entry);
     /// }
@@ -82,7 +84,8 @@ impl<'buf, Fd: AsFd> RawDir<'buf, Fd> {
     /// let mut buf = Vec::with_capacity(8192);
     /// 'read: loop {
     ///     'resize: {
-    ///         for entry in RawDir::new(&fd, buf.spare_capacity_mut()) {
+    ///         let mut iter = RawDir::new(&fd, buf.spare_capacity_mut());
+    ///         while let Some(entry) = iter.next() {
     ///             let entry = match entry {
     ///                 Err(Errno::INVAL) => break 'resize,
     ///                 r => r.unwrap(),
@@ -162,11 +165,13 @@ impl<'a> RawDirEntry<'a> {
     }
 }
 
-impl<'buf, Fd: AsFd> Iterator for RawDir<'buf, Fd> {
-    type Item = io::Result<RawDirEntry<'buf>>;
-
+impl<'buf, Fd: AsFd> RawDir<'buf, Fd> {
+    /// Identical to [Iterator::next] except that [Iterator::Item] borrows from self.
+    ///
+    /// Note: this interface will be broken to implement a stdlib iterator API with
+    /// GAT support once one becomes available.
     #[allow(unsafe_code)]
-    fn next(&mut self) -> Option<Self::Item> {
+    pub fn next(&mut self) -> Option<io::Result<RawDirEntry>> {
         loop {
             if self.offset < self.initialized {
                 let dirent_ptr = self.buf[self.offset..].as_ptr();

tests/fs/readdir.rs

@@ -56,24 +56,23 @@ fn read_entries(dir: &mut Dir) -> HashMap<String, DirEntry> {
 
 #[cfg(any(target_os = "android", target_os = "linux"))]
 fn test_raw_dir(buf: &mut [MaybeUninit<u8>]) {
+    use std::collections::HashSet;
     use std::io::{Seek, SeekFrom};
 
     use rustix::fd::AsFd;
-    use rustix::fs::{RawDir, RawDirEntry};
+    use rustix::fs::RawDir;
 
-    fn read_raw_entries<'a, Fd: AsFd>(
-        dir: &'a mut RawDir<'_, Fd>,
-    ) -> HashMap<String, RawDirEntry<'a>> {
-        let mut out = HashMap::new();
-        for entry in dir {
+    fn read_raw_entries<Fd: AsFd>(dir: &mut RawDir<Fd>) -> HashSet<String> {
+        let mut out = HashSet::new();
+        while let Some(entry) = dir.next() {
             let entry = entry.expect("non-error entry");
             let name = entry
                 .file_name()
                 .to_str()
                 .expect("utf8 filename")
                 .to_owned();
             if name != "." && name != ".." {
-                out.insert(name, entry);
+                out.insert(name);
             }
         }
         out