Auto merge of #77674 - cuviper:direntry-diet, r=dtolnay

unix/vxworks: make DirEntry slightly smaller

`DirEntry` contains a `ReadDir` handle, which used to just be a wrapper
on `Arc<InnerReadDir>`. Commit af75314 added `end_of_stream: bool`
which is not needed by `DirEntry`, but adds 8 bytes after padding. We
can let `DirEntry` have an `Arc<InnerReadDir>` directly to avoid that.

library/std/src/sys/unix/fs.rs

@@ -183,9 +183,14 @@ struct InnerReadDir {
     root: PathBuf,
 }
 
-#[derive(Clone)]
 pub struct ReadDir {
     inner: Arc<InnerReadDir>,
+    #[cfg(not(any(
+        target_os = "solaris",
+        target_os = "illumos",
+        target_os = "fuchsia",
+        target_os = "redox",
+    )))]
     end_of_stream: bool,
 }
 
@@ -196,7 +201,7 @@ unsafe impl Sync for Dir {}
 
 pub struct DirEntry {
     entry: dirent64,
-    dir: ReadDir,
+    dir: Arc<InnerReadDir>,
     // We need to store an owned copy of the entry name
     // on Solaris and Fuchsia because a) it uses a zero-length
     // array to store the name, b) its lifetime between readdir
@@ -443,7 +448,7 @@ impl Iterator for ReadDir {
                     name: slice::from_raw_parts(name as *const u8, namelen as usize)
                         .to_owned()
                         .into_boxed_slice(),
-                    dir: self.clone(),
+                    dir: Arc::clone(&self.inner),
                 };
                 if ret.name_bytes() != b"." && ret.name_bytes() != b".." {
                     return Some(Ok(ret));
@@ -464,7 +469,7 @@ impl Iterator for ReadDir {
         }
 
         unsafe {
-            let mut ret = DirEntry { entry: mem::zeroed(), dir: self.clone() };
+            let mut ret = DirEntry { entry: mem::zeroed(), dir: Arc::clone(&self.inner) };
             let mut entry_ptr = ptr::null_mut();
             loop {
                 if readdir64_r(self.inner.dirp.0, &mut ret.entry, &mut entry_ptr) != 0 {
@@ -497,7 +502,7 @@ impl Drop for Dir {
 
 impl DirEntry {
     pub fn path(&self) -> PathBuf {
-        self.dir.inner.root.join(OsStr::from_bytes(self.name_bytes()))
+        self.dir.root.join(OsStr::from_bytes(self.name_bytes()))
     }
 
     pub fn file_name(&self) -> OsString {
@@ -506,7 +511,7 @@ impl DirEntry {
 
     #[cfg(any(target_os = "linux", target_os = "emscripten", target_os = "android"))]
     pub fn metadata(&self) -> io::Result<FileAttr> {
-        let fd = cvt(unsafe { dirfd(self.dir.inner.dirp.0) })?;
+        let fd = cvt(unsafe { dirfd(self.dir.dirp.0) })?;
         let name = self.entry.d_name.as_ptr();
 
         cfg_has_statx! {
@@ -944,7 +949,16 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
             Err(Error::last_os_error())
         } else {
             let inner = InnerReadDir { dirp: Dir(ptr), root };
-            Ok(ReadDir { inner: Arc::new(inner), end_of_stream: false })
+            Ok(ReadDir {
+                inner: Arc::new(inner),
+                #[cfg(not(any(
+                    target_os = "solaris",
+                    target_os = "illumos",
+                    target_os = "fuchsia",
+                    target_os = "redox",
+                )))]
+                end_of_stream: false,
+            })
         }
     }
 }

library/std/src/sys/vxworks/fs.rs

@@ -27,7 +27,6 @@ struct InnerReadDir {
     root: PathBuf,
 }
 
-#[derive(Clone)]
 pub struct ReadDir {
     inner: Arc<InnerReadDir>,
     end_of_stream: bool,
@@ -40,7 +39,7 @@ unsafe impl Sync for Dir {}
 
 pub struct DirEntry {
     entry: dirent,
-    dir: ReadDir,
+    dir: Arc<InnerReadDir>,
 }
 
 #[derive(Clone, Debug)]
@@ -170,7 +169,7 @@ impl Iterator for ReadDir {
         }
 
         unsafe {
-            let mut ret = DirEntry { entry: mem::zeroed(), dir: self.clone() };
+            let mut ret = DirEntry { entry: mem::zeroed(), dir: Arc::clone(&self.inner) };
             let mut entry_ptr = ptr::null_mut();
             loop {
                 if readdir64_r(self.inner.dirp.0, &mut ret.entry, &mut entry_ptr) != 0 {
@@ -204,7 +203,7 @@ impl Drop for Dir {
 impl DirEntry {
     pub fn path(&self) -> PathBuf {
         use crate::sys::vxworks::ext::ffi::OsStrExt;
-        self.dir.inner.root.join(OsStr::from_bytes(self.name_bytes()))
+        self.dir.root.join(OsStr::from_bytes(self.name_bytes()))
     }
 
     pub fn file_name(&self) -> OsString {