added an example with coroutine stackoverflow

Author: dietmarkuehl

examples/CMakeLists.txt

@@ -6,6 +6,7 @@
 list(
     APPEND
     EXAMPLES
+    stackoverflow
     inspect
     playground
     sender-demo

examples/stackoverflow.cpp

@@ -0,0 +1,73 @@
+#include <beman/execution/execution.hpp>
+#include <coroutine>
+#include <iostream>
+#include <type_traits>
+#include <utility>
+
+namespace ex = beman::execution;
+
+struct task {
+    using sender_concept        = ex::sender_t;
+    using completion_signatures = ex::completion_signatures<ex::set_value_t()>;
+
+    struct base {
+        virtual void complete_value() noexcept = 0;
+    };
+
+    struct promise_type {
+        struct final_awaiter {
+            base* data;
+            bool  await_ready() noexcept { return false; }
+            auto  await_suspend(auto h) noexcept {
+                std::cout << "final_awaiter\n";
+                this->data->complete_value();
+                std::cout << "completed\n";
+            };
+            void await_resume() noexcept {}
+        };
+        std::suspend_always     initial_suspend() const noexcept { return {}; }
+        final_awaiter           final_suspend() const noexcept { return {this->data}; }
+        void                    unhandled_exception() const noexcept {}
+        std::coroutine_handle<> unhandled_stopped() { return std::coroutine_handle<>(); }
+        auto                    return_void() {}
+        auto get_return_object() { return task{std::coroutine_handle<promise_type>::from_promise(*this)}; }
+        template <::beman::execution::sender Sender>
+        auto await_transform(Sender&& sender) noexcept {
+            return ::beman::execution::as_awaitable(::std::forward<Sender>(sender), *this);
+        }
+
+        base* data{};
+    };
+
+    template <ex::receiver R>
+    struct state : base {
+
+        using operation_state_concept = ex::operation_state_t;
+        std::remove_cvref_t<R>              r;
+        std::coroutine_handle<promise_type> handle;
+
+        state(auto&& r, auto&& h) : r(std::forward<R>(r)), handle(std::move(h)) {}
+        void start() & noexcept {
+            this->handle.promise().data = this;
+            this->handle.resume();
+        }
+        void complete_value() noexcept override { ex::set_value(std::move(this->r)); }
+    };
+
+    std::coroutine_handle<promise_type> handle;
+
+    template <ex::receiver R>
+    auto connect(R&& r) && {
+        return state<R>(std::forward<R>(r), std::move(this->handle));
+    }
+};
+
+int main(int ac, char*[]) {
+    static_assert(ex::sender<task>);
+    ex::sync_wait([](int n) -> task {
+        for (int i{}; i < n; ++i) {
+            std::cout << "await=" << (co_await ex::just(i)) << "\n";
+        }
+        co_return;
+    }(ac < 2 ? 3 : 30000));
+}