2 files changed, 15 insertions, 1 deletions
diff --git a/library/std/src/sys/unix/mod.rs b/library/std/src/sys/unix/mod.rs
index 8e909aab7f0..1505878e18c 100644
--- a/library/std/src/sys/unix/mod.rs
+++ b/library/std/src/sys/unix/mod.rs
@@ -1,5 +1,6 @@
 #![allow(missing_docs, nonstandard_style)]
 
+use crate::ffi::CStr;
 use crate::io::ErrorKind;
 
 pub use self::rand::hashmap_random_keys;
@@ -66,6 +67,15 @@ pub unsafe fn init(argc: isize, argv: *const *const u8) {
     stack_overflow::init();
     args::init(argc, argv);
 
+    // Normally, `thread::spawn` will call `Thread::set_name` but since this thread
+    // already exists, we have to call it ourselves. We only do this on macos
+    // because some unix-like operating systems such as Linux share process-id and
+    // thread-id for the main thread and so renaming the main thread will rename the
+    // process and we only want to enable this on platforms we've tested.
+    if cfg!(target_os = "macos") {
+        thread::Thread::set_name(&CStr::from_bytes_with_nul_unchecked(b"main\0"));
+    }
+
     unsafe fn sanitize_standard_fds() {
         #[cfg(not(miri))]
         // The standard fds are always available in Miri.
diff --git a/library/std/src/sys/windows/mod.rs b/library/std/src/sys/windows/mod.rs
index 4e9d408291d..b3f6d2d0aae 100644
--- a/library/std/src/sys/windows/mod.rs
+++ b/library/std/src/sys/windows/mod.rs
@@ -1,6 +1,6 @@
 #![allow(missing_docs, nonstandard_style)]
 
-use crate::ffi::{OsStr, OsString};
+use crate::ffi::{CStr, OsStr, OsString};
 use crate::io::ErrorKind;
 use crate::os::windows::ffi::{OsStrExt, OsStringExt};
 use crate::path::PathBuf;
@@ -49,6 +49,10 @@ cfg_if::cfg_if! {
 // NOTE: this is not guaranteed to run, for example when Rust code is called externally.
 pub unsafe fn init(_argc: isize, _argv: *const *const u8) {
     stack_overflow::init();
+
+    // Normally, `thread::spawn` will call `Thread::set_name` but since this thread already
+    // exists, we have to call it ourselves.
+    thread::Thread::set_name(&CStr::from_bytes_with_nul_unchecked(b"main\0"));
 }
 
 // SAFETY: must be called only once during runtime cleanup.