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From: "iains at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/95615] [coroutines] Coroutine frame and promise is leaked
 if exception thrown from promise.initial_suspend()
Date: Mon, 15 Feb 2021 14:00:07 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95615

--- Comment #3 from Iain Sandoe <iains at gcc dot gnu.org> ---
Actually, I don't think the example goes far enough.

ISTM, [on exception in the places noted] that non-trivial DTORs for frame
copies of parms should be run after the GRO and promise DTOR but before the
frame is freed.

Do you agree? (if so I have a patch for this now)

So, I think the modified example below should print:

Y ()
Y (const Y&)
operator new()
Y (const Y&)
promise_type()
get_return_object()
task()
~task()
~promise_type()
~Y ()
operator delete
~Y ()
caught X
~Y ()

=3D=3D=3D=3D=3D=3D=3D
but *both* [master] GCC and clang print:

Y ()
Y (const Y&)
operator new()
Y (const Y&)
promise_type()
task()
~Y ()
~task()
~Y ()

=3D=3D=3D=3D=3D=3D=3D

#if __has_include(<coroutine>)
#include <coroutine>
#else
#include <experimental/coroutine>
namespace std {
    using namespace std::experimental;
}
#endif
#include <cstdio>

struct X {};

int Y_live =3D 0;

struct Y
{
  Y () { std::puts("Y ()"); Y_live++; }=20
  Y (const Y&) { std::puts("Y (const Y&)"); Y_live++; }=20
  ~Y () { std::puts("~Y ()"); Y_live--; }
};

struct task {
    struct promise_type {
        void* operator new(size_t sz) {
            std::puts("operator new()");
            return ::operator new(sz);
        }

        void operator delete(void* p, size_t sz) {
            std::puts("operator delete");
            return ::operator delete(p, sz);
        }

        promise_type() {
            std::puts("promise_type()");
            // throw X{};
        }

        ~promise_type() {
            std::puts("~promise_type()");
        }

        struct awaiter {
            bool await_ready() {
                //throw X{};
                return false;
            }
            void await_suspend(std::coroutine_handle<>) {
                //throw X{};
            }
            void await_resume() {
                //throw X{};
            }
        };

        awaiter initial_suspend() {
            // throw X{};
            return {};
        }

        task get_return_object() {
            // throw X{};
            return task{};
        }

        std::suspend_never final_suspend() noexcept { return {}; }
        void return_void() noexcept {}
        void unhandled_exception() noexcept {
            std::puts("unhandled_exception()");
        }
    };

    task() { std::puts("task()"); }
    ~task() { std::puts("~task()"); }
    task(task&&) { std::puts("task(task&&)"); }
};

task f(Y Val) {
    co_return;
}

int main() {
    Y Val;
    try {
        auto a =3D f(Val);
    } catch (X) {
        std::puts("caught X");
    }
}

=3D=3D=3D=3D=