fix(runtime): Box the main future to avoid blowing up the stack (#19155)

This fixes `Unhandled exception at [...] Stack overflow` on Windows,
caused by the large size of the main future.

1 files changed, 12 insertions, 0 deletions

diff --git a/runtime/tokio_util.rs b/runtime/tokio_util.rs
index ce6ef305f..d723006bd 100644
--- a/runtime/tokio_util.rs
+++ b/runtime/tokio_util.rs
@@ -16,14 +16,26 @@ pub fn create_basic_runtime() -> tokio::runtime::Runtime {
     .unwrap()
 }
 
+#[inline(always)]
 pub fn create_and_run_current_thread<F, R>(future: F) -> R
 where
   F: std::future::Future<Output = R> + 'static,
   R: Send + 'static,
 {
   let rt = create_basic_runtime();
+
+  // Since this is the main future, we want to box it in debug mode because it tends to be fairly
+  // large and the compiler won't optimize repeated copies. We also make this runtime factory
+  // function #[inline(always)] to avoid holding the unboxed, unused future on the stack.
+
+  #[cfg(debug_assertions)]
+  // SAFETY: this this is guaranteed to be running on a current-thread executor
+  let future = Box::pin(unsafe { MaskFutureAsSend::new(future) });
+
+  #[cfg(not(debug_assertions))]
   // SAFETY: this this is guaranteed to be running on a current-thread executor
   let future = unsafe { MaskFutureAsSend::new(future) };
+
   let join_handle = rt.spawn(future);
   rt.block_on(join_handle).unwrap().into_inner()
 }