std: add platform support for hexagon-unknown-qurt by androm3da · Pull Request #152084 · rust-lang/rust

androm3da · 2026-02-04T04:50:05Z

QuRT is not a unix target but provides POSIX-compatible threading, file I/O, and synchronization APIs. This implementation does not declare unix as a target family. Instead, it explicitly opts into the unix PAL and selects unix-based implementations for individual subsystems where QuRT's POSIX layer is sufficient.

Supported: alloc, threading, mutex, condvar, rwlock, once, thread parking, TLS, file system, file descriptors, stdio, I/O slices, I/O errors, is_terminal, env, paths, time, exit, personality/unwinding, backtrace

Stubbed; returns Err: process spawning, networking, pipes, hostname
Stubbed; returns empty: command-line args
Stubbed; panics: random

Platform modules:

New os::qurt module with platform-specific extensions (ffi, fs, io, raw)

rustbot · 2026-02-04T04:50:10Z

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androm3da · 2026-02-04T15:14:47Z

This PR depends on a newer version of the libc crate - maybe I'll let this PR hang here for a bit and check back in when it gets released and promoted?

joboet · 2026-02-07T15:21:04Z

This PR depends on a newer version of the libc crate - maybe I'll let this PR hang here for a bit and check back in when it gets released and promoted?

You need libc at 0.2.179, right? You can update libc here – but please keep it in a separate commit.

joboet · 2026-02-07T15:35:05Z

@rustbot author

rustbot · 2026-02-07T15:35:10Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

androm3da · 2026-02-08T18:25:04Z

This PR depends on a newer version of the libc crate - maybe I'll let this PR hang here for a bit and check back in when it gets released and promoted?

You need libc at 0.2.179, right? You can update libc here – but please keep it in a separate commit.

The commit I need - rust-lang/libc@9934c04 is not yet tagged/released. Or rather there is a ctest-* tag but I suspect that doesn't apply/not intended use for that tag. Should I try to execute a tag/release of libc, or just wait for that to happen naturally?

androm3da · 2026-02-17T06:16:27Z

This PR depends on a newer version of the libc crate - maybe I'll let this PR hang here for a bit and check back in when it gets released and promoted?

You need libc at 0.2.179, right? You can update libc here – but please keep it in a separate commit.

The commit I need - rust-lang/libc@9934c04 is not yet tagged/released. Or rather there is a ctest-* tag but I suspect that doesn't apply/not intended use for that tag. Should I try to execute a tag/release of libc, or just wait for that to happen naturally?

Ah - I see now that it appears in 0.2.181 and there's already a PR open for that (#150752). I'll rebase when that lands.

androm3da · 2026-05-06T17:41:32Z

Can you provide some more details? By expanding the "etc.". For example time and randomness aren't covered by your list. And want to know which APIs are stubbed in a way that results in panics vs. those that return Err results.

I've updated the PR description like so:

Supported: alloc, threading, mutex, condvar, rwlock, once, thread parking, TLS, file system, file descriptors, stdio, I/O slices, I/O errors, is_terminal, env, paths, time, exit, personality/unwinding, backtrace

Stubbed; returns Err: process spawning, networking, pipes, hostname
Stubbed; returns empty: command-line args
Stubbed; panics: random

nia-e · 2026-05-13T16:30:37Z

@@ -114,7 +114,7 @@ pub(crate) fn get_result_from_exit_code(
        Some(TR_OK) => TestResult::TrOk,
        #[cfg(windows)]
        Some(STATUS_FAIL_FAST_EXCEPTION) => TestResult::TrFailed,
-        #[cfg(unix)]
+        #[cfg(all(unix, not(target_os = "qurt")))]


So, is qurt unix or not for cfg purposes? This seems to not be consistent throughout the PR

View changes since the review

Sorry, I'll make it consistent.

joshtriplett · 2026-05-13T16:33:19Z

@@ -1,6 +1,11 @@
 #![forbid(unsafe_op_in_unsafe_fn)]

 cfg_select! {
+    // QuRT uses unsupported pipes since it doesn't support process spawning
+    target_os = "qurt" => {


This is no longer needed since qurt is no longer unix.

View changes since the review

Fixed, thanks

nia-e · 2026-05-13T16:35:23Z

The conclusion from today's libs meeting was that this target is (given what we're seeing) Not Unix, but properly defining what is unix is best left for a refactor of the cfgs we expose

joboet

@rust-lang/libs-api how do you feel about the API additions here? Adding an instant-deprecated stat definitions seems a bit weird to me.

View changes since this review

joboet · 2026-05-21T13:56:38Z

+- **`thread::yield_now()`**: Calls `sched_yield` which is stubbed to `abort`;
+  use `thread::sleep(Duration::from_millis(0))` as an alternative


Couldn't std do that? yield_now aborting seems bad, even having it be a noop is better.

joboet · 2026-05-21T13:57:59Z

@@ -227,6 +231,7 @@ impl<'a> AsRawFd for io::StdinLock<'a> {
 }

 #[stable(feature = "asraw_stdio_locks", since = "1.35.0")]
+#[cfg(not(target_os = "qurt"))]


But stdio is supported, right? Why wouldn't this be available?

joboet · 2026-05-21T13:59:32Z

This isn't used anymore, right? If so, then could you remove this change please?

joboet · 2026-05-21T14:03:49Z

@@ -3,6 +3,10 @@ use crate::fmt;

 pub struct Args {}

+pub unsafe fn init(_argc: isize, _argv: *const *const u8) {


This should be gated for QuRT, otherwise other unsupported targets will complain about the unused function.

joboet · 2026-05-21T14:07:05Z

@@ -124,6 +129,7 @@ pub fn set_permissions(path: &Path, perm: FilePermissions) -> io::Result<()> {
 pub fn set_permissions_nofollow(path: &Path, perm: crate::fs::Permissions) -> io::Result<()> {
    use crate::fs::OpenOptions;

+    #[cfg_attr(any(target_os = "espidf", target_os = "horizon"), allow(unused_mut))]


Thanks! I suggest #[expect] instead of #[allow], it means we'll notice if the attribute becomes unnecessary.

joboet · 2026-05-21T14:12:04Z

Please undo this change, this is no longer needed.

joboet · 2026-05-21T14:14:52Z

Insert the config here instead of adding a manual fallback.

joboet · 2026-05-21T14:15:00Z

+#[cfg(target_os = "qurt")]
+pub fn set_name(_name: &CStr) {
+    // QuRT doesn't support pthread_setname_np
+}
+


Suggested change

#[cfg(target_os = "qurt")]

pub fn set_name(_name: &CStr) {

// QuRT doesn't support pthread_setname_np

}

joboet · 2026-05-21T14:21:41Z

+    -C "link-args=${QURTLIB}/crt1.o ${HEXLIB}/crt0.o ${HEXLIB}/init.o ${QURTLIB}/debugmon.o" \
+    -C "link-args=-Wl,--section-start=.start=0x40000" \
+    -C "link-args=-Wl,--defsym=sched_yield=abort" \
+    -C "link-args=-Wl,--defsym=unsetenv=abort" \


Making remove_env panic seems like a much nicer way of handling this.

joboet · 2026-05-21T14:22:55Z

@@ -31,9 +31,9 @@ cfg_select! {
        unix,
        windows,
        target_os = "psp",
+        target_os = "qurt",


You might be able to get rid of the weird symbol redefinitions by not linking to them here and just aborting in panic_unwind instead.

There are a number of other targets that don't support unwinding either, I suggest you have a look at the Hermit implementation in particular.

Remove unix family from hexagon-unknown-qurt target spec and instead explicitly opt into unix implementations where applicable, following the pattern used by similar unix-adjacent targets. The target uses the unix PAL and explicitly selects unix implementations for the supported features. Modules that remain unsupported for qurt: process spawning, networking and pipes.

Update documentation with details about how to leverage qurt, now that there's some level of libstd support

Remove spurious #[allow(unused_imports)] added before `use super::platform::fs::MetadataExt as _` in os/unix/fs.rs. This import is used and the annotation is not needed.

Remove #[cfg(not(target_os = "qurt"))] guard on getppid() in sys/process/unix/common.rs. QuRT's libc provides getpid/getppid, so no special-casing is needed.

Remove target_os = "qurt" from the libunwind branch in library/unwind/src/lib.rs. QuRT's _Unwind_* symbols are provided by libc_eh (linked via build.rs), not by Rust's in-tree libunwind. panic_unwind for qurt falls through to dummy.rs which aborts, so no libunwind symbols are needed from this crate.

Move qurt's set_name no-op from thread/unix.rs into thread/mod.rs by adding target_os = "qurt" to the cfg lists that select unsupported::set_name. This is the canonical pattern used by other targets (newlib, l4re, wasi, etc.) that don't support thread naming, rather than adding a per-OS stub function in unix.rs.

Make unsetenv panic for qurt rather than calling libc::unsetenv, which is not available. This causes std::env::remove_var to panic on qurt, which is the correct behaviour for an unsupported operation. The linker stub --defsym=unsetenv=abort is no longer needed.

Remove qurt exclusions from AsRawFd impls for Stdin/Stdout/Stderr and their lock types in os/fd/raw.rs. QuRT's libc defines STDIN_FILENO, STDOUT_FILENO and STDERR_FILENO, and stdio is functional on this platform, so these impls should be available.

Gate the no-op args::init in sys/args/unsupported.rs with #[cfg(target_os = "qurt")]. Without this, all other targets using the unsupported args module would see an unused function warning. Only qurt needs it there because it uses the unix PAL (which calls args::init) but is not in the unix family and so falls through to the unsupported args module.

Change #[allow(unused_mut)] to #[expect(unused_mut)] for the set_permissions_nofollow options binding, so the compiler will warn if the attribute becomes unnecessary in the future.

Remove as_raw_stat() from qurt's MetadataExt trait and its raw::stat struct definition. as_raw_stat() has been deprecated since 1.8.0 in favour of the individual accessor methods; adding it to a brand-new platform only to immediately deprecate it is unnecessary. This follows the pattern of newer platforms like AIX that only expose the metadata_ext2 accessors.

Update docs to reflect the sys-layer fixes: - remove_var now panics rather than silently failing (unsetenv is not available; the panic happens at the sys layer so no linker stub needed) - yield_now is implemented as sleep(Duration::ZERO); sched_yield linker stub no longer needed; remove the known-limitation entry entirely - Remove the yield_now and unsetenv --defsym stubs from both the build.rs and rustc direct-invocation examples

Fix compilation after rebase: - ffi.rs: migrate sealed traits to pub impl(self) syntax - fd/unix.rs: add u8 type parameter to BorrowedCursor - fs/unix.rs: remove redundant cfg guard on lock() methods - unwind/lib.rs: explicitly list qurt for libunwind (no longer in unix family)

rustbot · 2026-07-08T04:51:36Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

rustbot assigned joboet Feb 4, 2026