From 7123c5808cce2339515f7efece4e0640112bcd31 Mon Sep 17 00:00:00 2001
From: Eric Niebler <eniebler@nvidia.com>
Date: Thu, 14 Dec 2023 13:25:29 -0800
Subject: [PATCH] fix an exception safety bug in schedule_from

---
 include/stdexec/execution.hpp | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/include/stdexec/execution.hpp b/include/stdexec/execution.hpp
index 9acb81368..f195f5dab 100644
--- a/include/stdexec/execution.hpp
+++ b/include/stdexec/execution.hpp
@@ -4272,9 +4272,6 @@ namespace stdexec {
         : __data_()
         , __state2_(connect(schedule(__sched), __receiver2_t{this})) {
       }
-
-      void __complete() noexcept {
-      }
     };
 
     struct schedule_from_t {
@@ -4324,7 +4321,16 @@ namespace stdexec {
           // we can forward the completion from within the scheduler's
           // execution context.
           using __async_result = __decayed_tuple<_Tag, _Args...>;
-          __state.__data_.template emplace<__async_result>(_Tag(), (_Args&&) __args...);
+          if constexpr (__nothrow_constructible_from<__async_result, _Tag, _Args...>) {
+            __state.__data_.template emplace<__async_result>(_Tag(), (_Args&&) __args...);
+          } else {
+            try {
+              __state.__data_.template emplace<__async_result>(_Tag(), (_Args&&) __args...);
+            } catch(...) {
+              set_error(std::move(__rcvr), std::current_exception());
+              return;
+            }
+          }
           // Enqueue the schedule operation so the completion happens
           // on the scheduler's execution context.
           stdexec::start(__state.__state2_);