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Enable statx on all Linux targets and short-circuit it for musl #159540

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1bf22c1
Make statx available on all Linux targets
strophy Apr 13, 2026
bd844a5
bootstrap: Set RUST_LIBC_UNSTABLE_MUSL_V1_2_3=1
Gelbpunkt Jul 19, 2026
5c51ad5
std: Unconditionally use statx on musl targets
Gelbpunkt Jul 19, 2026
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124 changes: 69 additions & 55 deletions library/std/src/sys/fs/unix.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@
#[cfg(test)]
mod tests;

#[cfg(all(target_os = "linux", target_env = "gnu"))]
#[cfg(target_os = "linux")]
use libc::c_char;
#[cfg(any(
all(target_os = "linux", not(target_env = "musl")),
Expand Down Expand Up @@ -95,7 +95,7 @@ use crate::sys::fd::FileDesc;
pub use crate::sys::fs::common::exists;
use crate::sys::helpers::run_path_with_cstr;
use crate::sys::time::SystemTime;
#[cfg(all(target_os = "linux", target_env = "gnu"))]
#[cfg(all(target_os = "linux", not(target_env = "musl")))]
use crate::sys::weak::syscall;
#[cfg(target_os = "android")]
use crate::sys::weak::weak;
Expand Down Expand Up @@ -126,14 +126,14 @@ mod runtime_symbols {

pub struct File(FileDesc);

// FIXME: This should be available on Linux with all `target_env`.
// But currently only glibc exposes `statx` fn and structs.
// We don't want to import unverified raw C structs here directly.
// statx is available on Linux when:
// - target_env = "gnu": added in glibc >= 2.28
// - target_env = "musl": added in musl >= 1.2.5
// https://github.com/rust-lang/rust/pull/67774
macro_rules! cfg_has_statx {
({ $($then_tt:tt)* } else { $($else_tt:tt)* }) => {
cfg_select! {
all(target_os = "linux", target_env = "gnu") => {
target_os = "linux" => {
$($then_tt)*
}
_ => {
Expand All @@ -142,7 +142,7 @@ macro_rules! cfg_has_statx {
}
};
($($block_inner:tt)*) => {
#[cfg(all(target_os = "linux", target_env = "gnu"))]
#[cfg(target_os = "linux")]
{
$($block_inner)*
}
Expand Down Expand Up @@ -174,67 +174,81 @@ cfg_has_statx! {{
// We prefer `statx` on Linux if available, which contains file creation time,
// as well as 64-bit timestamps of all kinds.
// Default `stat64` contains no creation time and may have 32-bit `time_t`.
//
// We can unconditionally assume that musl targets have `statx` because musl
// takes care of falling back to fstatat and our musl version baseline is
// 1.2.5, which is the first release with statx support.
unsafe fn try_statx(
fd: c_int,
path: *const c_char,
flags: i32,
mask: u32,
) -> Option<io::Result<FileAttr>> {
use crate::sync::atomic::{Atomic, AtomicU8, Ordering};

// Linux kernel prior to 4.11 or glibc prior to glibc 2.28 don't support `statx`.
// We check for it on first failure and remember availability to avoid having to
// do it again.
#[repr(u8)]
enum STATX_STATE{ Unknown = 0, Present, Unavailable }
static STATX_SAVED_STATE: Atomic<u8> = AtomicU8::new(STATX_STATE::Unknown as u8);

syscall!(
fn statx(
fd: c_int,
pathname: *const c_char,
flags: c_int,
mask: libc::c_uint,
statxbuf: *mut libc::statx,
) -> c_int;
);

let statx_availability = STATX_SAVED_STATE.load(Ordering::Relaxed);
if statx_availability == STATX_STATE::Unavailable as u8 {
return None;
}

let mut buf: libc::statx = mem::zeroed();
if let Err(err) = cvt(statx(fd, path, flags, mask, &mut buf)) {
if STATX_SAVED_STATE.load(Ordering::Relaxed) == STATX_STATE::Present as u8 {

#[cfg(target_env = "musl")]
{
if let Err(err) = cvt(libc::statx(fd, path, flags, mask, &mut buf)) {
return Some(Err(err));
}
}
#[cfg(not(target_env = "musl"))]
{
use crate::sync::atomic::{Atomic, AtomicU8, Ordering};

// Linux kernel prior to 4.11 or glibc prior to glibc 2.28 don't support `statx`.
// We check for it on first failure and remember availability to avoid having to
// do it again.
#[repr(u8)]
enum STATX_STATE{ Unknown = 0, Present, Unavailable }
static STATX_SAVED_STATE: Atomic<u8> = AtomicU8::new(STATX_STATE::Unknown as u8);

syscall!(
fn statx(
fd: c_int,
pathname: *const c_char,
flags: c_int,
mask: libc::c_uint,
statxbuf: *mut libc::statx,
) -> c_int;
);

let statx_availability = STATX_SAVED_STATE.load(Ordering::Relaxed);
if statx_availability == STATX_STATE::Unavailable as u8 {
return None;
}

if let Err(err) = cvt(statx(fd, path, flags, mask, &mut buf)) {
if STATX_SAVED_STATE.load(Ordering::Relaxed) == STATX_STATE::Present as u8 {
return Some(Err(err));
}

// We're not yet entirely sure whether `statx` is usable on this kernel
// or not. Syscalls can return errors from things other than the kernel
// per se, e.g. `EPERM` can be returned if seccomp is used to block the
// syscall, or `ENOSYS` might be returned from a faulty FUSE driver.
//
// Availability is checked by performing a call which expects `EFAULT`
// if the syscall is usable.
//
// See: https://github.com/rust-lang/rust/issues/65662
//
// FIXME what about transient conditions like `ENOMEM`?
let err2 = cvt(statx(0, ptr::null(), 0, libc::STATX_BASIC_STATS | libc::STATX_BTIME, ptr::null_mut()))
.err()
.and_then(|e| e.raw_os_error());
if err2 == Some(libc::EFAULT) {
// We're not yet entirely sure whether `statx` is usable on this kernel
// or not. Syscalls can return errors from things other than the kernel
// per se, e.g. `EPERM` can be returned if seccomp is used to block the
// syscall, or `ENOSYS` might be returned from a faulty FUSE driver.
//
// Availability is checked by performing a call which expects `EFAULT`
// if the syscall is usable.
//
// See: https://github.com/rust-lang/rust/issues/65662
//
// FIXME what about transient conditions like `ENOMEM`?
let err2 = cvt(statx(0, ptr::null(), 0, libc::STATX_BASIC_STATS | libc::STATX_BTIME, ptr::null_mut()))
.err()
.and_then(|e| e.raw_os_error());
if err2 == Some(libc::EFAULT) {
STATX_SAVED_STATE.store(STATX_STATE::Present as u8, Ordering::Relaxed);
return Some(Err(err));
} else {
STATX_SAVED_STATE.store(STATX_STATE::Unavailable as u8, Ordering::Relaxed);
return None;
}
}
if statx_availability == STATX_STATE::Unknown as u8 {
STATX_SAVED_STATE.store(STATX_STATE::Present as u8, Ordering::Relaxed);
return Some(Err(err));
} else {
STATX_SAVED_STATE.store(STATX_STATE::Unavailable as u8, Ordering::Relaxed);
return None;
}
}
if statx_availability == STATX_STATE::Unknown as u8 {
STATX_SAVED_STATE.store(STATX_STATE::Present as u8, Ordering::Relaxed);
}

// We cannot fill `stat64` exhaustively because of private padding fields.
let mut stat: stat64 = mem::zeroed();
Expand Down
7 changes: 7 additions & 0 deletions src/bootstrap/src/core/builder/cargo.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1305,6 +1305,13 @@ impl Builder<'_> {
// The libc build script emits check-cfg flags only when this environment variable is set,
// so this line allows the use of custom libcs.
cargo.env("LIBC_CHECK_CFG", "1");
// The libc crate has a musl version baseline that is much lower than that of the musl
// targets in the Rust compiler at the moment. This unfortunately means that features only
// supported in newer musl releases like time64 and, for example statx, are not available by
// default unless opted into via an environment variable. The version baseline of the Rust
// compiler targets is currently 1.2.5, so we can set the variable to get access to statx in
// std, amongst other things.
cargo.env("RUST_LIBC_UNSTABLE_MUSL_V1_2_3", "1");

@bjorn3 bjorn3 Jul 19, 2026 •
edited by rustbot
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This would break with build-std, right? Cargo wouldn't set this env var.

View changes since the review

@Gelbpunkt Gelbpunkt Jul 19, 2026

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That's a good point, right. Not sure how to go about that. I presume we'd want to modify cargo to set the variable for rustc processes while compiling std? That sounds fairly complicated

@Mark-Simulacrum Mark-Simulacrum Jul 20, 2026

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Can we make this a regular cargo feature prefixed with unstable or internal-do-not-use or something like that and then enable it here?


let mut lint_flags = Vec::new();

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