From 8b2b6359f97ee9ac8fb1b5c35e86211222d02574 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Fri, 20 Dec 2024 15:03:51 +0100
Subject: [PATCH] mri: add track_caller to thread spawning methods for better
 backtraces

---
 library/std/src/sys/pal/unix/thread.rs    | 1 +
 library/std/src/sys/pal/windows/thread.rs | 1 +
 library/std/src/thread/mod.rs             | 4 ++++
 3 files changed, 6 insertions(+)

diff --git a/library/std/src/sys/pal/unix/thread.rs b/library/std/src/sys/pal/unix/thread.rs
index 131a6e81b1e92..e360ba0f6d7d8 100644
--- a/library/std/src/sys/pal/unix/thread.rs
+++ b/library/std/src/sys/pal/unix/thread.rs
@@ -45,6 +45,7 @@ unsafe impl Sync for Thread {}
 
 impl Thread {
     // unsafe: see thread::Builder::spawn_unchecked for safety requirements
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub unsafe fn new(stack: usize, p: Box<dyn FnOnce()>) -> io::Result<Thread> {
         let p = Box::into_raw(Box::new(p));
         let mut native: libc::pthread_t = mem::zeroed();
diff --git a/library/std/src/sys/pal/windows/thread.rs b/library/std/src/sys/pal/windows/thread.rs
index 2c8ce42f4148b..45e52cf4d047f 100644
--- a/library/std/src/sys/pal/windows/thread.rs
+++ b/library/std/src/sys/pal/windows/thread.rs
@@ -19,6 +19,7 @@ pub struct Thread {
 
 impl Thread {
     // unsafe: see thread::Builder::spawn_unchecked for safety requirements
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub unsafe fn new(stack: usize, p: Box<dyn FnOnce()>) -> io::Result<Thread> {
         let p = Box::into_raw(Box::new(p));
 
diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs
index cfbf6548a380c..85ee369ca2b66 100644
--- a/library/std/src/thread/mod.rs
+++ b/library/std/src/thread/mod.rs
@@ -391,6 +391,7 @@ impl Builder {
     /// handler.join().unwrap();
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub fn spawn<F, T>(self, f: F) -> io::Result<JoinHandle<T>>
     where
         F: FnOnce() -> T,
@@ -458,6 +459,7 @@ impl Builder {
     ///
     /// [`io::Result`]: crate::io::Result
     #[stable(feature = "thread_spawn_unchecked", since = "1.82.0")]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub unsafe fn spawn_unchecked<F, T>(self, f: F) -> io::Result<JoinHandle<T>>
     where
         F: FnOnce() -> T,
@@ -467,6 +469,7 @@ impl Builder {
         Ok(JoinHandle(unsafe { self.spawn_unchecked_(f, None) }?))
     }
 
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     unsafe fn spawn_unchecked_<'scope, F, T>(
         self,
         f: F,
@@ -721,6 +724,7 @@ impl Builder {
 /// [`join`]: JoinHandle::join
 /// [`Err`]: crate::result::Result::Err
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub fn spawn<F, T>(f: F) -> JoinHandle<T>
 where
     F: FnOnce() -> T,