Rollup merge of rust-lang#92778 - tavianator:linux-readdir-no-r, r=joshtriplett

fs: Use readdir() instead of readdir_r() on Linux and Android See rust-lang#40021 for more details. Fixes rust-lang#86649. Fixes rust-lang#34668.

Author: matthiaskrgr

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

@@ -34,7 +34,20 @@ use libc::c_char;
 use libc::dirfd;
 #[cfg(any(target_os = "linux", target_os = "emscripten"))]
 use libc::fstatat64;
+#[cfg(any(
+ target_os = "android",
+ target_os = "solaris",
+ target_os = "fuchsia",
+ target_os = "redox",
+ target_os = "illumos"
+))]
+use libc::readdir as readdir64;
+#[cfg(target_os = "linux")]
+use libc::readdir64;
+#[cfg(any(target_os = "emscripten", target_os = "l4re"))]
+use libc::readdir64_r;
 #[cfg(not(any(
+ target_os = "android",
  target_os = "linux",
  target_os = "emscripten",
  target_os = "solaris",
@@ -60,9 +73,7 @@ use libc::{
  lstat as lstat64, off_t as off64_t, open as open64, stat as stat64,
 };
 #[cfg(any(target_os = "linux", target_os = "emscripten", target_os = "l4re"))]
-use libc::{
- dirent64, fstat64, ftruncate64, lseek64, lstat64, off64_t, open64, readdir64_r, stat64,
-};
+use libc::{dirent64, fstat64, ftruncate64, lseek64, lstat64, off64_t, open64, stat64};
 
 pub use crate::sys_common::fs::try_exists;
 
@@ -202,6 +213,8 @@ struct InnerReadDir {
 pub struct ReadDir {
  inner: Arc<InnerReadDir>,
  #[cfg(not(any(
+ target_os = "android",
+ target_os = "linux",
  target_os = "solaris",
  target_os = "illumos",
  target_os = "fuchsia",
@@ -218,11 +231,12 @@ unsafe impl Sync for Dir {}
 pub struct DirEntry {
  entry: dirent64,
  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
- // calls is not guaranteed.
+ // We need to store an owned copy of the entry name on platforms that use
+ // readdir() (not readdir_r()), because a) struct dirent may use a flexible
+ // array to store the name, b) it lives only until the next readdir() call.
  #[cfg(any(
+ target_os = "android",
+ target_os = "linux",
  target_os = "solaris",
  target_os = "illumos",
  target_os = "fuchsia",
@@ -449,6 +463,8 @@ impl Iterator for ReadDir {
  type Item = io::Result<DirEntry>;
 
  #[cfg(any(
+ target_os = "android",
+ target_os = "linux",
  target_os = "solaris",
  target_os = "fuchsia",
  target_os = "redox",
@@ -457,12 +473,13 @@ impl Iterator for ReadDir {
  fn next(&mut self) -> Option<io::Result<DirEntry>> {
  unsafe {
  loop {
- // Although readdir_r(3) would be a correct function to use here because
- // of the thread safety, on Illumos and Fuchsia the readdir(3C) function
- // is safe to use in threaded applications and it is generally preferred
- // over the readdir_r(3C) function.
+ // As of POSIX.1-2017, readdir() is not required to be thread safe; only
+ // readdir_r() is. However, readdir_r() cannot correctly handle platforms
+ // with unlimited or variable NAME_MAX. Many modern platforms guarantee
+ // thread safety for readdir() as long an individual DIR* is not accessed
+ // concurrently, which is sufficient for Rust.
  super::os::set_errno(0);
- let entry_ptr = libc::readdir(self.inner.dirp.0);
+ let entry_ptr = readdir64(self.inner.dirp.0);
  if entry_ptr.is_null() {
  // null can mean either the end is reached or an error occurred.
  // So we had to clear errno beforehand to check for an error now.
@@ -486,6 +503,8 @@ impl Iterator for ReadDir {
  }
 
  #[cfg(not(any(
+ target_os = "android",
+ target_os = "linux",
  target_os = "solaris",
  target_os = "fuchsia",
  target_os = "redox",
@@ -531,17 +550,17 @@ impl Drop for Dir {
 
 impl DirEntry {
  pub fn path(&self) -> PathBuf {
- self.dir.root.join(OsStr::from_bytes(self.name_bytes()))
+ self.dir.root.join(self.file_name_os_str())
  }
 
  pub fn file_name(&self) -> OsString {
- OsStr::from_bytes(self.name_bytes()).to_os_string()
+ self.file_name_os_str().to_os_string()
  }
 
  #[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.dirp.0) })?;
- let name = self.entry.d_name.as_ptr();
+ let name = self.name_cstr().as_ptr();
 
  cfg_has_statx! {
  if let Some(ret) = unsafe { try_statx(
@@ -639,29 +658,21 @@ impl DirEntry {
  )
  }
  }
- #[cfg(any(
- target_os = "android",
- target_os = "linux",
- target_os = "emscripten",
- target_os = "l4re",
- target_os = "haiku",
- target_os = "vxworks",
- target_os = "espidf"
- ))]
- fn name_bytes(&self) -> &[u8] {
- unsafe { CStr::from_ptr(self.entry.d_name.as_ptr()).to_bytes() }
- }
- #[cfg(any(
- target_os = "solaris",
- target_os = "illumos",
- target_os = "fuchsia",
- target_os = "redox"
- ))]
+ #[cfg(not(any(
+ target_os = "macos",
+ target_os = "ios",
+ target_os = "netbsd",
+ target_os = "openbsd",
+ target_os = "freebsd",
+ target_os = "dragonfly"
+ )))]
  fn name_bytes(&self) -> &[u8] {
- self.name.as_bytes()
+ self.name_cstr().to_bytes()
  }
 
  #[cfg(not(any(
+ target_os = "android",
+ target_os = "linux",
  target_os = "solaris",
  target_os = "illumos",
  target_os = "fuchsia",
@@ -670,7 +681,14 @@ impl DirEntry {
  fn name_cstr(&self) -> &CStr {
  unsafe { CStr::from_ptr(self.entry.d_name.as_ptr()) }
  }
- #[cfg(any(target_os = "solaris", target_os = "illumos", target_os = "fuchsia"))]
+ #[cfg(any(
+ target_os = "android",
+ target_os = "linux",
+ target_os = "solaris",
+ target_os = "illumos",
+ target_os = "fuchsia",
+ target_os = "redox"
+ ))]
  fn name_cstr(&self) -> &CStr {
  &self.name
  }
@@ -1076,6 +1094,8 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
  Ok(ReadDir {
  inner: Arc::new(inner),
  #[cfg(not(any(
+ target_os = "android",
+ target_os = "linux",
  target_os = "solaris",
  target_os = "illumos",
  target_os = "fuchsia",
@@ -1615,6 +1635,8 @@ mod remove_dir_impl {
  ReadDir {
  inner: Arc::new(InnerReadDir { dirp, root: dummy_root }),
  #[cfg(not(any(
+ target_os = "android",
+ target_os = "linux",
  target_os = "solaris",
  target_os = "illumos",
  target_os = "fuchsia",

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

@@ -75,7 +75,7 @@ pub fn errno() -> i32 {
 }
 
 /// Sets the platform-specific value of errno
-#[cfg(all(not(target_os = "linux"), not(target_os = "dragonfly"), not(target_os = "vxworks")))] // needed for readdir and syscall!
+#[cfg(all(not(target_os = "dragonfly"), not(target_os = "vxworks")))] // needed for readdir and syscall!
 #[allow(dead_code)] // but not all target cfgs actually end up using it
 pub fn set_errno(e: i32) {
  unsafe { *errno_location() = e as c_int }