The following was obtained by running:
$ cargo +1.39.0 valgrind --bin leakruntime

   Analyzing `target/debug/leakruntime`
       Error Leaked 40 B
        Info at malloc (vg_replace_malloc.c:309)
             at alloc::alloc::alloc (alloc.rs:84)
             at alloc::alloc::exchange_malloc (alloc.rs:206)
             at std::sync::mutex::Mutex<T>::new (mutex.rs:170)
             at piper::event::Event::inner (event.rs:139)
             at piper::event::Event::notify_one (event.rs:104)
             at <piper::mutex::MutexGuard<T> as core::ops::drop::Drop>::drop (mutex.rs:265)
             at core::ptr::real_drop_in_place (mod.rs:175)
             at smol::reactor::Reactor::insert_io (reactor.rs:126)
             at smol::async_io::Async<T>::new (async_io.rs:143)
             at smol::io_event::IoEvent::new (io_event.rs:44)
             at smol::thread_local::ThreadLocalExecutor::new (thread_local.rs:48)
       Error Leaked 40 B
        Info at malloc (vg_replace_malloc.c:309)
             at alloc::alloc::alloc (alloc.rs:84)
             at alloc::alloc::exchange_malloc (alloc.rs:206)
             at std::sync::mutex::Mutex<T>::new (mutex.rs:170)
             at piper::event::Event::inner (event.rs:139)
             at piper::event::Event::notify_one (event.rs:104)
             at <piper::mutex::MutexGuard<T> as core::ops::drop::Drop>::drop (mutex.rs:265)
             at core::ptr::real_drop_in_place (mod.rs:175)
             at smol::reactor::Reactor::fire_timers (reactor.rs:230)
             at smol::reactor::ReactorLock::react (reactor.rs:253)
             at smol::reactor::ReactorLock::wait (reactor.rs:247)
             at smol::run::react (run.rs:216)
       Error Leaked 72 B
        Info at malloc (vg_replace_malloc.c:309)
             at alloc::alloc::alloc (alloc.rs:84)
             at alloc::alloc::exchange_malloc (alloc.rs:206)
             at alloc::sync::Arc<T>::new (sync.rs:302)
             at piper::event::Event::inner (event.rs:137)
             at piper::event::Event::notify_one (event.rs:104)
             at <piper::mutex::MutexGuard<T> as core::ops::drop::Drop>::drop (mutex.rs:265)
             at core::ptr::real_drop_in_place (mod.rs:175)
             at smol::reactor::Reactor::insert_io (reactor.rs:126)
             at smol::async_io::Async<T>::new (async_io.rs:143)
             at smol::io_event::IoEvent::new (io_event.rs:44)
             at smol::thread_local::ThreadLocalExecutor::new (thread_local.rs:48)
       Error Leaked 72 B
        Info at malloc (vg_replace_malloc.c:309)
             at alloc::alloc::alloc (alloc.rs:84)
             at alloc::alloc::exchange_malloc (alloc.rs:206)
             at alloc::sync::Arc<T>::new (sync.rs:302)
             at piper::event::Event::inner (event.rs:137)
             at piper::event::Event::notify_one (event.rs:104)
             at <piper::mutex::MutexGuard<T> as core::ops::drop::Drop>::drop (mutex.rs:265)
             at core::ptr::real_drop_in_place (mod.rs:175)
             at smol::reactor::Reactor::fire_timers (reactor.rs:230)
             at smol::reactor::ReactorLock::react (reactor.rs:253)
             at smol::reactor::ReactorLock::wait (reactor.rs:247)
             at smol::run::react (run.rs:216)
       Error Leaked 120 B
        Info at malloc (vg_replace_malloc.c:309)
             at alloc::alloc::alloc (alloc.rs:84)
             at alloc::alloc::exchange_malloc (alloc.rs:206)
             at std::sync::mutex::Mutex<T>::new (mutex.rs:170)
             at piper::event::Event::inner (event.rs:139)
             at piper::event::Event::notify_one (event.rs:104)
             at <piper::mutex::MutexGuard<T> as core::ops::drop::Drop>::drop (mutex.rs:265)
             at core::ptr::real_drop_in_place (mod.rs:175)
             at smol::reactor::ReactorLock::react (reactor.rs:287)
             at smol::reactor::ReactorLock::wait (reactor.rs:247)
             at smol::run::react (run.rs:216)
             at smol::run::run::{{closure}} (run.rs:155)
       Error Leaked 120 B
        Info at malloc (vg_replace_malloc.c:309)
             at alloc::alloc::alloc (alloc.rs:84)
             at alloc::alloc::exchange_malloc (alloc.rs:206)
             at alloc::sync::Arc<T>::new (sync.rs:302)
             at async_task::waker_fn::waker_fn (waker_fn.rs:9)
             at smol::block_on::block_on::CACHE::__init (block_on.rs:52)
             at core::ops::function::FnOnce::call_once (function.rs:227)
             at std::thread::local::lazy::LazyKeyInner<T>::initialize (local.rs:290)
             at std::thread::local::fast::Key<T>::try_initialize (local.rs:431)
             at std::thread::local::fast::Key<T>::get (local.rs:416)
             at smol::block_on::block_on::CACHE::__getit (<::std::thread::local::__thread_local_inner macros>:29)
             at std::thread::local::LocalKey<T>::try_with (local.rs:259)
       Error Leaked 168 B
        Info at malloc (vg_replace_malloc.c:309)
             at alloc::alloc::alloc (alloc.rs:84)
             at alloc::alloc::exchange_malloc (alloc.rs:206)
             at alloc::sync::Arc<T>::new (sync.rs:302)
             at async_task::waker_fn::waker_fn (waker_fn.rs:9)
             at smol::run::run (run.rs:105)
             at async_std::rt::RUNTIME::{{closure}}::{{closure}} (mod.rs:19)
             at std::sys_common::backtrace::__rust_begin_short_backtrace (backtrace.rs:126)
             at std::thread::Builder::spawn_unchecked::{{closure}}::{{closure}} (mod.rs:470)
             at <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once (panic.rs:315)
             at std::panicking::try::do_call (panicking.rs:292)
             at __rust_maybe_catch_panic (lib.rs:80)
       Error Leaked 200 B
        Info at malloc (vg_replace_malloc.c:309)
             at alloc::alloc::alloc (alloc.rs:84)
             at alloc::alloc::exchange_malloc (alloc.rs:206)
             at std::sync::mutex::Mutex<T>::new (mutex.rs:170)
             at piper::event::Event::inner (event.rs:139)
             at piper::event::Event::notify_one (event.rs:104)
             at <piper::mutex::MutexGuard<T> as core::ops::drop::Drop>::drop (mutex.rs:265)
             at core::ptr::real_drop_in_place (mod.rs:175)
             at smol::reactor::Source::poll_io (reactor.rs:362)
             at smol::async_io::Async<T>::with::{{closure}}::{{closure}} (async_io.rs:301)
             at <futures_util::future::poll_fn::PollFn<F> as core::future::future::Future>::poll (poll_fn.rs:54)
             at std::future::poll_with_tls_context::{{closure}} (future.rs:121)
       Error Leaked 216 B
        Info at malloc (vg_replace_malloc.c:309)
             at alloc::alloc::alloc (alloc.rs:84)
             at alloc::alloc::exchange_malloc (alloc.rs:206)
             at alloc::sync::Arc<T>::new (sync.rs:302)
             at piper::event::Event::inner (event.rs:137)
             at piper::event::Event::notify_one (event.rs:104)
             at <piper::mutex::MutexGuard<T> as core::ops::drop::Drop>::drop (mutex.rs:265)
             at core::ptr::real_drop_in_place (mod.rs:175)
             at smol::reactor::ReactorLock::react (reactor.rs:287)
             at smol::reactor::ReactorLock::wait (reactor.rs:247)
             at smol::run::react (run.rs:216)
             at smol::run::run::{{closure}} (run.rs:155)
       Error Leaked 360 B
        Info at malloc (vg_replace_malloc.c:309)
             at alloc::alloc::alloc (alloc.rs:84)
             at alloc::alloc::exchange_malloc (alloc.rs:206)
             at alloc::sync::Arc<T>::new (sync.rs:302)
             at piper::event::Event::inner (event.rs:137)
             at piper::event::Event::notify_one (event.rs:104)
             at <piper::mutex::MutexGuard<T> as core::ops::drop::Drop>::drop (mutex.rs:265)
             at core::ptr::real_drop_in_place (mod.rs:175)
             at smol::reactor::Source::poll_io (reactor.rs:362)
             at smol::async_io::Async<T>::with::{{closure}}::{{closure}} (async_io.rs:301)
             at <futures_util::future::poll_fn::PollFn<F> as core::future::future::Future>::poll (poll_fn.rs:54)
             at std::future::poll_with_tls_context::{{closure}} (future.rs:121)
       Error Leaked 2.2 kiB
        Info at calloc (vg_replace_malloc.c:762)
             at allocate_dtv
             at _dl_allocate_tls
             at pthread_create@@GLIBC_2.2.5
             at std::sys::unix::thread::Thread::new (thread.rs:67)
             at std::thread::Builder::spawn_unchecked (mod.rs:489)
             at std::thread::Builder::spawn (mod.rs:382)
             at async_std::rt::RUNTIME::{{closure}} (mod.rs:17)
             at core::ops::function::FnOnce::call_once (function.rs:227)
             at core::ops::function::FnOnce::call_once (function.rs:227)
             at once_cell::sync::Lazy<T,F>::force::{{closure}} (lib.rs:910)
             at once_cell::sync::OnceCell<T>::get_or_init::{{closure}} (lib.rs:763)
     Summary Leaked 3.6 kiB total