Use the OS thread name by default for the current thread

Author: ChrisDenton

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/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_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()