Use the OS thread name by default if THREAD_INFO has not been initialized

library/std/src/sys/pal/hermit/thread.rs

@@ -2,7 +2,7 @@
 
 use super::abi;
 use super::thread_local_dtor::run_dtors;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -71,6 +71,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     #[inline]
     pub fn sleep(dur: Duration) {
         unsafe {

library/std/src/sys/pal/itron/thread.rs

@@ -8,7 +8,7 @@ use super::{
 };
 use crate::{
     cell::UnsafeCell,
-    ffi::CStr,
+    ffi::{CStr, CString},
     hint, io,
     mem::ManuallyDrop,
     num::NonZero,
@@ -204,6 +204,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         for timeout in dur2reltims(dur) {
             expect_success(unsafe { abi::dly_tsk(timeout) }, &"dly_tsk");

library/std/src/sys/pal/sgx/thread.rs

@@ -1,6 +1,6 @@
 #![cfg_attr(test, allow(dead_code))] // why is this necessary?
 use super::unsupported;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::num::NonZero;
 use crate::time::Duration;
@@ -133,6 +133,10 @@ impl Thread {
         // which succeeds as-is with the SGX target.
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         usercalls::wait_timeout(0, dur, || true);
     }

library/std/src/sys/pal/teeos/thread.rs

@@ -1,7 +1,7 @@
 use core::convert::TryInto;
 
 use crate::cmp;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -101,6 +101,10 @@ impl Thread {
         // contact the teeos rustzone team.
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     /// only main thread could wait for sometime in teeos
     pub fn sleep(dur: Duration) {
         let sleep_millis = dur.as_millis();

library/std/src/sys/pal/uefi/thread.rs

@@ -1,5 +1,5 @@
 use super::unsupported;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::num::NonZero;
 use crate::ptr::NonNull;
@@ -23,6 +23,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         let boot_services: NonNull<r_efi::efi::BootServices> =
             crate::os::uefi::env::boot_services().expect("can't sleep").cast();

library/std/src/sys/pal/unix/thread.rs

@@ -1,5 +1,5 @@
 use crate::cmp;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -225,6 +225,44 @@ impl Thread {
         // Newlib, Emscripten, and VxWorks have no way to set a thread name.
     }
 
+    #[cfg(target_os = "linux")]
+    pub fn get_name() -> Option<CString> {
+        const TASK_COMM_LEN: usize = 16;
+        let mut name = vec![0u8; TASK_COMM_LEN];
+        let res = unsafe {
+            libc::pthread_getname_np(libc::pthread_self(), name.as_mut_ptr().cast(), name.len())
+        };
+        if res != 0 {
+            return None;
+        }
+        name.truncate(name.iter().position(|&c| c == 0)?);
+        CString::new(name).ok()
+    }
+
+    #[cfg(any(target_os = "macos", target_os = "ios", target_os = "tvos", target_os = "watchos"))]
+    pub fn get_name() -> Option<CString> {
+        let mut name = vec![0u8; libc::MAXTHREADNAMESIZE];
+        let res = unsafe {
+            libc::pthread_getname_np(libc::pthread_self(), name.as_mut_ptr().cast(), name.len())
+        };
+        if res != 0 {
+            return None;
+        }
+        name.truncate(name.iter().position(|&c| c == 0)?);
+        CString::new(name).ok()
+    }
+
+    #[cfg(not(any(
+        target_os = "linux",
+        target_os = "macos",
+        target_os = "ios",
+        target_os = "tvos",
+        target_os = "watchos"
+    )))]
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     #[cfg(not(target_os = "espidf"))]
     pub fn sleep(dur: Duration) {
         let mut secs = dur.as_secs();

library/std/src/sys/pal/unsupported/thread.rs

@@ -1,5 +1,5 @@
 use super::unsupported;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::num::NonZero;
 use crate::time::Duration;
@@ -22,6 +22,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(_dur: Duration) {
         panic!("can't sleep");
     }

library/std/src/sys/pal/wasi/thread.rs

@@ -1,4 +1,4 @@
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -134,6 +134,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         let nanos = dur.as_nanos();
         assert!(nanos <= u64::MAX as u128);

library/std/src/sys/pal/windows/c.rs

@@ -344,6 +344,12 @@ compat_fn_with_fallback! {
         SetLastError(ERROR_CALL_NOT_IMPLEMENTED as DWORD); E_NOTIMPL
     }
 
+    // >= Win10 1607
+    // https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-getthreaddescription
+    pub fn GetThreadDescription(hthread: HANDLE, lpthreaddescription: *mut PWSTR) -> HRESULT {
+        SetLastError(ERROR_CALL_NOT_IMPLEMENTED as DWORD); E_NOTIMPL
+    }
+
     // >= Win8 / Server 2012
     // https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getsystemtimepreciseasfiletime
     pub fn GetSystemTimePreciseAsFileTime(lpsystemtimeasfiletime: *mut FILETIME) -> () {

library/std/src/sys/pal/windows/c/bindings.txt

@@ -1923,6 +1923,7 @@ Windows.Win32.Foundation.HANDLE_FLAG_INHERIT
 Windows.Win32.Foundation.HANDLE_FLAG_PROTECT_FROM_CLOSE
 Windows.Win32.Foundation.HANDLE_FLAGS
 Windows.Win32.Foundation.HMODULE
+Windows.Win32.Foundation.LocalFree
 Windows.Win32.Foundation.MAX_PATH
 Windows.Win32.Foundation.NO_ERROR
 Windows.Win32.Foundation.NTSTATUS

library/std/src/sys/pal/windows/c/windows_sys.rs

@@ -379,6 +379,10 @@ extern "system" {
     ) -> BOOL;
 }
 #[link(name = "kernel32")]
+extern "system" {
+    pub fn LocalFree(hmem: HLOCAL) -> HLOCAL;
+}
+#[link(name = "kernel32")]
 extern "system" {
     pub fn MoveFileExW(
         lpexistingfilename: PCWSTR,
@@ -3441,6 +3445,7 @@ pub type HANDLE_FLAGS = u32;
 pub const HANDLE_FLAG_INHERIT: HANDLE_FLAGS = 1u32;
 pub const HANDLE_FLAG_PROTECT_FROM_CLOSE: HANDLE_FLAGS = 2u32;
 pub const HIGH_PRIORITY_CLASS: PROCESS_CREATION_FLAGS = 128u32;
+pub type HLOCAL = *mut ::core::ffi::c_void;
 pub type HMODULE = *mut ::core::ffi::c_void;
 pub type HRESULT = i32;
 pub const IDLE_PRIORITY_CLASS: PROCESS_CREATION_FLAGS = 64u32;

library/std/src/sys/pal/windows/thread.rs

@@ -9,7 +9,7 @@ use crate::sys::handle::Handle;
 use crate::sys::stack_overflow;
 use crate::sys_common::FromInner;
 use crate::time::Duration;
-
+use alloc::ffi::CString;
 use core::ffi::c_void;
 
 use super::time::WaitableTimer;
@@ -71,6 +71,29 @@ impl Thread {
         };
     }
 
+    pub fn get_name() -> Option<CString> {
+        unsafe {
+            let mut ptr = core::ptr::null_mut();
+            let result = c::GetThreadDescription(c::GetCurrentThread(), &mut ptr);
+            if result < 0 {
+                return None;
+            }
+            let name = String::from_utf16_lossy({
+                let mut len = 0;
+                while *ptr.add(len) != 0 {
+                    len += 1;
+                }
+                core::slice::from_raw_parts(ptr, len)
+            })
+            .into_bytes();
+            // Attempt to free the memory.
+            // This should never fail but if it does then there's not much we can do about it.
+            let result = c::LocalFree(ptr.cast::<c_void>());
+            debug_assert!(result.is_null());
+            if name.is_empty() { None } else { Some(CString::from_vec_unchecked(name)) }
+        }
+    }
+
     pub fn join(self) {
         let rc = unsafe { c::WaitForSingleObject(self.handle.as_raw_handle(), c::INFINITE) };
         if rc == c::WAIT_FAILED {

library/std/src/sys/pal/xous/thread.rs

@@ -1,4 +1,4 @@
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::num::NonZero;
 use crate::os::xous::ffi::{
@@ -113,6 +113,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         // Because the sleep server works on units of `usized milliseconds`, split
         // the messages up into these chunks. This means we may run into issues

library/std/src/sys_common/thread_info.rs

@@ -1,6 +1,7 @@
 #![allow(dead_code)] // stack_guard isn't used right now on all platforms
 
 use crate::cell::OnceCell;
+use crate::sys;
 use crate::sys::thread::guard::Guard;
 use crate::thread::Thread;
 
@@ -23,7 +24,8 @@ impl ThreadInfo {
     {
         THREAD_INFO
             .try_with(move |thread_info| {
-                let thread = thread_info.thread.get_or_init(|| Thread::new(None));
+                let thread =
+                    thread_info.thread.get_or_init(|| Thread::new(sys::thread::Thread::get_name()));
                 f(thread, &thread_info.stack_guard)
             })
             .ok()

library/std/src/thread/tests.rs

@@ -69,6 +69,25 @@ fn test_named_thread_truncation() {
     result.unwrap().join().unwrap();
 }
 
+#[cfg(any(
+    target_os = "windows",
+    target_os = "linux",
+    target_os = "macos",
+    target_os = "ios",
+    target_os = "tvos",
+    target_os = "watchos"
+))]
+#[test]
+fn test_get_os_named_thread() {
+    use crate::sys::thread::Thread;
+    let handler = thread::spawn(|| {
+        let name = c"test me please";
+        Thread::set_name(name);
+        assert_eq!(name, Thread::get_name().unwrap().as_c_str());
+    });
+    handler.join().unwrap();
+}
+
 #[test]
 #[should_panic]
 fn test_invalid_named_thread() {