Print thread ID in panic message if thread name is unknown

`panic!` does not print any identifying information for threads that are
unnamed. However, in many cases, the thread ID can be determined.

This changes the panic message from something like this:

    thread '<unnamed>' panicked at src/main.rs:3:5:
    explicit panic

To something like this:

    thread '<unnamed>' (0xff9bf) panicked at src/main.rs:3:5:
    explicit panic

Stack overflow messages are updated as well.

This change applies to both named and unnamed threads. The ID printed is
the OS integer thread ID rather than the Rust thread ID, which should
also be what debuggers print.

Author: tgross35

library/std/src/panicking.rs

@@ -269,6 +269,7 @@ fn default_hook(info: &PanicHookInfo<'_>) {
 
         thread::with_current_name(|name| {
             let name = name.unwrap_or("<unnamed>");
+            let tid = thread::current_os_id().unwrap_or_default();
 
             // Try to write the panic message to a buffer first to prevent other concurrent outputs
             // interleaving with it.
@@ -277,7 +278,7 @@ fn default_hook(info: &PanicHookInfo<'_>) {
 
             let write_msg = |dst: &mut dyn crate::io::Write| {
                 // We add a newline to ensure the panic message appears at the start of a line.
-                writeln!(dst, "\nthread '{name}' panicked at {location}:\n{msg}")
+                writeln!(dst, "\nthread '{name}' ({tid:#x}) panicked at {location}:\n{msg}")
             };
 
             if write_msg(&mut cursor).is_ok() {

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

@@ -103,6 +103,10 @@ impl Thread {
     }
 }
 
+pub(crate) fn current_os_id() -> Option<u64> {
+    None
+}
+
 pub fn available_parallelism() -> io::Result<NonZero<usize>> {
     unsafe { Ok(NonZero::new_unchecked(hermit_abi::available_parallelism())) }
 }

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

@@ -349,6 +349,10 @@ unsafe fn terminate_and_delete_current_task() -> ! {
     unsafe { crate::hint::unreachable_unchecked() };
 }
 
+pub(crate) fn current_os_id() -> Option<u64> {
+    None
+}
+
 pub fn available_parallelism() -> io::Result<NonZero<usize>> {
     super::unsupported()
 }

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

@@ -132,6 +132,10 @@ impl Drop for Thread {
     }
 }
 
+pub(crate) fn current_os_id() -> Option<u64> {
+    None
+}
+
 // Note: Both `sched_getaffinity` and `sysconf` are available but not functional on
 // teeos, so this function always returns an Error!
 pub fn available_parallelism() -> io::Result<NonZero<usize>> {

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

@@ -44,6 +44,10 @@ impl Thread {
     }
 }
 
+pub(crate) fn current_os_id() -> Option<u64> {
+    None
+}
+
 pub fn available_parallelism() -> io::Result<NonZero<usize>> {
     // UEFI is single threaded
     Ok(NonZero::new(1).unwrap())

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

@@ -120,7 +120,8 @@ mod imp {
                     && thread_info.guard_page_range.contains(&fault_addr)
                 {
                     let name = thread_info.thread_name.as_deref().unwrap_or("<unknown>");
-                    rtprintpanic!("\nthread '{name}' has overflowed its stack\n");
+                    let tid = crate::thread::current_os_id().unwrap_or_default();
+                    rtprintpanic!("\nthread '{name}' ({tid:#x}) has overflowed its stack\n");
                     rtabort!("stack overflow");
                 }
             })
@@ -696,7 +697,8 @@ mod imp {
             if code == c::EXCEPTION_STACK_OVERFLOW {
                 crate::thread::with_current_name(|name| {
                     let name = name.unwrap_or("<unknown>");
-                    rtprintpanic!("\nthread '{name}' has overflowed its stack\n");
+                    let tid = crate::thread::current_os_id().unwrap_or_default();
+                    rtprintpanic!("\nthread '{name}' ({tid:#x}) has overflowed its stack\n");
                 });
             }
             c::EXCEPTION_CONTINUE_SEARCH

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

@@ -318,6 +318,44 @@ impl Drop for Thread {
     }
 }
 
+pub(crate) fn current_os_id() -> Option<u64> {
+    // Most Unix platforms have a way to query an integer ID of the current thread, all with
+    // slightly different spellings.
+    cfg_if::cfg_if! {
+        // Most platforms have a function returning a `pid_t` or int, which is an `i32`.
+        if #[cfg(any(target_os = "android", target_os = "linux", target_os = "nto"))] {
+            // SAFETY: FFI call with no preconditions.
+            let id: libc::pid_t = unsafe { libc::gettid() };
+            Some(id as u64)
+        } else if #[cfg(target_os = "openbsd")] {
+            // SAFETY: FFI call with no preconditions.
+            let id: libc::pid_t = unsafe { libc::getthrid() };
+            Some(id as u64)
+        } else if #[cfg(target_os = "freebsd")] {
+            // SAFETY: FFI call with no preconditions.
+            let id: libc::c_int = unsafe { libc::pthread_getthreadid_np() };
+            Some(id as u64)
+        } else if #[cfg(target_os = "netbsd")] {
+            // SAFETY: FFI call with no preconditions.
+            let id: libc::lwpid_t = unsafe { libc::_lwp_self() };
+            Some(id as u64)
+        } else if #[cfg(target_vendor = "apple")] {
+            // Apple allows querying arbitrary thread IDs, `thread=NULL` queries the current thread.
+            let mut id = 0u64;
+            // SAFETY: `thread_id` is a valid pointer, no other preconditions.
+            let status: libc::c_int = unsafe { libc::pthread_threadid_np(0, &mut id) };
+            if status == 0 {
+                Some(id)
+            } else {
+                None
+            }
+        } else {
+            // As a fallback, return the pid which can be used to help identify a crashing process.
+            Some(super::os::getpid().into())
+        }
+    }
+}
+
 #[cfg(any(
     target_os = "linux",
     target_os = "nto",

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

@@ -31,6 +31,10 @@ impl Thread {
     }
 }
 
+pub(crate) fn current_os_id() -> Option<u64> {
+    None
+}
+
 pub fn available_parallelism() -> io::Result<NonZero<usize>> {
     unsupported()
 }

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

@@ -186,6 +186,10 @@ impl Thread {
     }
 }
 
+pub(crate) fn current_os_id() -> Option<u64> {
+    None
+}
+
 pub fn available_parallelism() -> io::Result<NonZero<usize>> {
     cfg_if::cfg_if! {
         if #[cfg(target_feature = "atomics")] {

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

@@ -2177,6 +2177,7 @@ GetSystemInfo
 GetSystemTimeAsFileTime
 GetSystemTimePreciseAsFileTime
 GetTempPathW
+GetThreadId
 GetUserProfileDirectoryW
 GetWindowsDirectoryW
 HANDLE

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

@@ -61,6 +61,7 @@ windows_targets::link!("kernel32.dll" "system" fn GetSystemInfo(lpsysteminfo : *
 windows_targets::link!("kernel32.dll" "system" fn GetSystemTimeAsFileTime(lpsystemtimeasfiletime : *mut FILETIME));
 windows_targets::link!("kernel32.dll" "system" fn GetSystemTimePreciseAsFileTime(lpsystemtimeasfiletime : *mut FILETIME));
 windows_targets::link!("kernel32.dll" "system" fn GetTempPathW(nbufferlength : u32, lpbuffer : PWSTR) -> u32);
+windows_targets::link!("kernel32.dll" "system" fn GetThreadId(thread : HANDLE) -> u32);
 windows_targets::link!("userenv.dll" "system" fn GetUserProfileDirectoryW(htoken : HANDLE, lpprofiledir : PWSTR, lpcchsize : *mut u32) -> BOOL);
 windows_targets::link!("kernel32.dll" "system" fn GetWindowsDirectoryW(lpbuffer : PWSTR, usize : u32) -> u32);
 windows_targets::link!("kernel32.dll" "system" fn InitOnceBeginInitialize(lpinitonce : *mut INIT_ONCE, dwflags : u32, fpending : *mut BOOL, lpcontext : *mut *mut core::ffi::c_void) -> BOOL);

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

@@ -20,7 +20,8 @@ unsafe extern "system" fn vectored_handler(ExceptionInfo: *mut c::EXCEPTION_POIN
         if code == c::EXCEPTION_STACK_OVERFLOW {
             thread::with_current_name(|name| {
                 let name = name.unwrap_or("<unknown>");
-                rtprintpanic!("\nthread '{name}' has overflowed its stack\n");
+                let tid = thread::current_os_id().unwrap_or_default();
+                rtprintpanic!("\nthread '{name}' ({tid:#x}) has overflowed its stack\n");
             });
         }
         c::EXCEPTION_CONTINUE_SEARCH

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

@@ -115,6 +115,14 @@ impl Thread {
     }
 }
 
+pub(crate) fn current_os_id() -> Option<u64> {
+    // SAFETY: FFI call with no preconditions.
+    let id: u32 = unsafe { c::GetThreadId(c::GetCurrentThread()) };
+
+    // A return value of 0 indicates failed lookup.
+    if id == 0 { None } else { Some(id.into()) }
+}
+
 pub fn available_parallelism() -> io::Result<NonZero<usize>> {
     let res = unsafe {
         let mut sysinfo: c::SYSTEM_INFO = crate::mem::zeroed();

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

@@ -133,6 +133,10 @@ impl Thread {
     }
 }
 
+pub(crate) fn current_os_id() -> Option<u64> {
+    None
+}
+
 pub fn available_parallelism() -> io::Result<NonZero<usize>> {
     // We're unicore right now.
     Ok(unsafe { NonZero::new_unchecked(1) })

library/std/src/thread/current.rs

@@ -1,4 +1,4 @@
-use super::{Thread, ThreadId};
+use super::{Thread, ThreadId, imp};
 use crate::mem::ManuallyDrop;
 use crate::ptr;
 use crate::sys::thread_local::local_pointer;
@@ -148,6 +148,15 @@ pub(crate) fn current_id() -> ThreadId {
     id::get_or_init()
 }
 
+/// Gets the OS thread ID of the thread that invokes it, if available.
+///
+/// We use a `u64` to fit either integer or pointer IDs on all platforms without excess `cfg`. This
+/// is a "best effort" approach for diagnostics and is allowed to fall back to a non-unique ID (such
+/// as PID) if the thread ID cannot be retrieved.
+pub(crate) fn current_os_id() -> Option<u64> {
+    imp::current_os_id()
+}
+
 /// Gets a reference to the handle of the thread that invokes it, if the handle
 /// has been initialized.
 pub(super) fn try_with_current<F, R>(f: F) -> R

library/std/src/thread/mod.rs

@@ -183,7 +183,7 @@ mod current;
 
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use current::current;
-pub(crate) use current::{current_id, current_or_unnamed, drop_current};
+pub(crate) use current::{current_id, current_or_unnamed, current_os_id, drop_current};
 use current::{set_current, try_with_current};
 
 mod spawnhook;

library/std/src/thread/tests.rs

@@ -346,6 +346,19 @@ fn test_thread_id_not_equal() {
     assert!(thread::current().id() != spawned_id);
 }
 
+#[test]
+fn test_thread_os_id_not_equal() {
+    let spawned_id = thread::spawn(|| thread::current_os_id()).join().unwrap();
+    let current_id = thread::current_os_id();
+
+    // Spot check on platforms that we know should be able to query a TID.
+    if cfg!(target_os = "linux") || cfg!(target_vendor = "apple") || cfg!(target_os = "windows") {
+        assert!(spawned_id.is_some());
+        assert!(current_id.is_some());
+        assert!(current_id != spawned_id);
+    }
+}
+
 #[test]
 fn test_scoped_threads_drop_result_before_join() {
     let actually_finished = &AtomicBool::new(false);

src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind1.stderr

@@ -1,5 +1,5 @@
 
-thread 'main' panicked at tests/fail/function_calls/exported_symbol_bad_unwind1.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/function_calls/exported_symbol_bad_unwind1.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect

src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.both.stderr

@@ -1,10 +1,10 @@
 
-thread 'main' panicked at tests/fail/function_calls/exported_symbol_bad_unwind2.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/function_calls/exported_symbol_bad_unwind2.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 
-thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
+thread 'main' ($HEX) panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 panic in a function that cannot unwind
 stack backtrace:
 thread caused non-unwinding panic. aborting.

src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.definition.stderr

@@ -1,10 +1,10 @@
 
-thread 'main' panicked at tests/fail/function_calls/exported_symbol_bad_unwind2.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/function_calls/exported_symbol_bad_unwind2.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 
-thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
+thread 'main' ($HEX) panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 panic in a function that cannot unwind
 stack backtrace:
 thread caused non-unwinding panic. aborting.

src/tools/miri/tests/fail/function_calls/exported_symbol_bad_unwind2.extern_block.stderr

@@ -1,5 +1,5 @@
 
-thread 'main' panicked at tests/fail/function_calls/exported_symbol_bad_unwind2.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/function_calls/exported_symbol_bad_unwind2.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect

src/tools/miri/tests/fail/function_calls/return_pointer_on_unwind.stderr

@@ -1,5 +1,5 @@
 
-thread 'main' panicked at tests/fail/function_calls/return_pointer_on_unwind.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/function_calls/return_pointer_on_unwind.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect

src/tools/miri/tests/fail/intrinsics/uninit_uninhabited_type.stderr

@@ -1,5 +1,5 @@
 
-thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
+thread 'main' ($HEX) panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 aborted execution: attempted to instantiate uninhabited type `!`
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect

src/tools/miri/tests/fail/intrinsics/zero_fn_ptr.stderr

@@ -1,5 +1,5 @@
 
-thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
+thread 'main' ($HEX) panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 aborted execution: attempted to zero-initialize type `fn()`, which is invalid
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect

src/tools/miri/tests/fail/panic/abort_unwind.stderr

@@ -1,10 +1,10 @@
 
-thread 'main' panicked at tests/fail/panic/abort_unwind.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/panic/abort_unwind.rs:LL:CC:
 PANIC!!!
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 
-thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
+thread 'main' ($HEX) panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 panic in a function that cannot unwind
 stack backtrace:
 thread caused non-unwinding panic. aborting.

src/tools/miri/tests/fail/panic/bad_unwind.stderr

@@ -1,5 +1,5 @@
 
-thread 'main' panicked at tests/fail/panic/bad_unwind.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/panic/bad_unwind.rs:LL:CC:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect

src/tools/miri/tests/fail/panic/double_panic.stderr

@@ -1,14 +1,14 @@
 
-thread 'main' panicked at tests/fail/panic/double_panic.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/panic/double_panic.rs:LL:CC:
 first
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
 
-thread 'main' panicked at tests/fail/panic/double_panic.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/panic/double_panic.rs:LL:CC:
 second
 stack backtrace:
 
-thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
+thread 'main' ($HEX) panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
 panic in a destructor during cleanup
 thread caused non-unwinding panic. aborting.
 error: abnormal termination: the program aborted execution

src/tools/miri/tests/fail/panic/panic_abort1.stderr

@@ -1,5 +1,5 @@
 
-thread 'main' panicked at tests/fail/panic/panic_abort1.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/panic/panic_abort1.rs:LL:CC:
 panicking from libstd
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect

src/tools/miri/tests/fail/panic/panic_abort2.stderr

@@ -1,5 +1,5 @@
 
-thread 'main' panicked at tests/fail/panic/panic_abort2.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/panic/panic_abort2.rs:LL:CC:
 42-panicking from libstd
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect

src/tools/miri/tests/fail/panic/panic_abort3.stderr

@@ -1,5 +1,5 @@
 
-thread 'main' panicked at tests/fail/panic/panic_abort3.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/panic/panic_abort3.rs:LL:CC:
 panicking from libcore
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect

src/tools/miri/tests/fail/panic/panic_abort4.stderr

@@ -1,5 +1,5 @@
 
-thread 'main' panicked at tests/fail/panic/panic_abort4.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/panic/panic_abort4.rs:LL:CC:
 42-panicking from libcore
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect

src/tools/miri/tests/fail/panic/tls_macro_const_drop_panic.stderr

@@ -1,5 +1,5 @@
 
-thread $NAME panicked at tests/fail/panic/tls_macro_const_drop_panic.rs:LL:CC:
+thread $NAME ($HEX) panicked at tests/fail/panic/tls_macro_const_drop_panic.rs:LL:CC:
 ow
 fatal runtime error: thread local panicked on drop, aborting
 error: abnormal termination: the program aborted execution

src/tools/miri/tests/fail/panic/tls_macro_drop_panic.stderr

@@ -1,5 +1,5 @@
 
-thread $NAME panicked at tests/fail/panic/tls_macro_drop_panic.rs:LL:CC:
+thread $NAME ($HEX) panicked at tests/fail/panic/tls_macro_drop_panic.rs:LL:CC:
 ow
 fatal runtime error: thread local panicked on drop, aborting
 error: abnormal termination: the program aborted execution

src/tools/miri/tests/fail/ptr_swap_nonoverlapping.stderr

@@ -1,5 +1,5 @@
 
-thread 'main' panicked at tests/fail/ptr_swap_nonoverlapping.rs:LL:CC:
+thread 'main' ($HEX) panicked at tests/fail/ptr_swap_nonoverlapping.rs:LL:CC:
 unsafe precondition(s) violated: ptr::swap_nonoverlapping requires that both pointer arguments are aligned and non-null and the specified memory ranges do not overlap
 
 This indicates a bug in the program. This Undefined Behavior check is optional, and cannot be relied on for safety.