https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101243
Bug ID: 101243 Summary: Coroutine lambda capture is destroyed twice Product: gcc Version: 11.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: victor.burckel at gmail dot com Target Milestone: --- In a corourtine expecting a std::function<void()> parameter, passing a temporary lambda with a capture results in the capture being destroyed twice: See it on gldbolt, gcc vs clang outputs https://godbolt.org/z/jx9Yh5cqM #include <fmt/core.h> #include <coroutine> #include <functional> #ifdef __clang__ namespace std::experimental { using std::coroutine_handle; using std::coroutine_traits; } // namespace std::experimental #endif struct task { struct promise_type; using handle_type = std::coroutine_handle<promise_type>; struct promise_type { auto initial_suspend() noexcept { return std::suspend_always{}; } auto final_suspend() noexcept { return std::suspend_always{}; } void return_void() noexcept {} task get_return_object() noexcept { return task{handle_type::from_promise(*this)}; } void unhandled_exception() noexcept {} }; task(handle_type h) : h{h} {} ~task() { if (h) { fmt::print("destroying coroutine\n"); h.destroy(); fmt::print("coroutine destroyed\n"); } } bool await_ready() const noexcept { return false; } bool await_suspend(std::coroutine_handle<>) noexcept { h.resume(); return true; } void await_resume() noexcept {} void resume() { h.resume(); } handle_type h; }; struct S { S() { fmt::print("S::S()\n"); } S(const S&) { fmt::print("S::S(const S&)\n"); } S(S&&) { fmt::print("S::S(S&&)\n"); } ~S() { fmt::print("S::~S()\n"); } }; task g(std::function<void()>) { fmt::print("in g()\n"); co_return; } task f() { fmt::print("calling g()\n"); co_await g([s=S{}] {}); fmt::print("g called\n"); } int main() { auto task = f(); fmt::print("resuming f\n"); task.resume(); fmt::print("resuming f\n"); task.resume(); } Gcc outputs: resuming f calling g() S::S() S::S(S&&) in g() resuming f destroying coroutine S::~S() coroutine destroyed S::~S() S::~S() g called destroying coroutine coroutine destroyed While clang outputs: resuming f calling g() S::S() S::S(S&&) in g() resuming f destroying coroutine S::~S() coroutine destroyed S::~S() g called destroying coroutine coroutine destroyed