Fix WASM block producer panic

frame/system/src/lib.rs

@@ -591,11 +591,14 @@ pub mod pallet {
 
  /// Events deposited for the current block.
  ///
- /// NOTE: This storage item is explicitly unbounded since it is never intended to be read
- /// from within the runtime.
+ /// NOTE: The item is unbound and should therefore never be read from storage.
+ /// It could otherwise inflate the PoV size of a block.
+ ///
+ /// Events have a large in-memory size. Box the events to not go out-of-memory
+ /// just in case someone still reads them from within the runtime.
  #[pallet::storage]
  pub(super) type Events<T: Config> =
- StorageValue<_, Vec<EventRecord<T::Event, T::Hash>>, ValueQuery>;
+ StorageValue<_, Vec<Box<EventRecord<T::Event, T::Hash>>>, ValueQuery>;
 
  /// The number of events in the `Events<T>` list.
  #[pallet::storage]
@@ -1213,7 +1216,7 @@ impl<T: Config> Pallet<T> {
  old_event_count
  };
 
- Events::<T>::append(&event);
+ Events::<T>::append(event);
 
  for topic in topics {
  <EventTopics<T>>::append(topic, &(block_number, event_idx));
@@ -1380,14 +1383,16 @@ impl<T: Config> Pallet<T> {
  /// items for any behavior like this.
  #[cfg(any(feature = "std", feature = "runtime-benchmarks", test))]
  pub fn events() -> Vec<EventRecord<T::Event, T::Hash>> {
- Self::read_events_no_consensus()
+ // Dereferencing the events here is fine since we are not in the
+ // memory-restricted runtime.
+ Self::read_events_no_consensus().into_iter().map(|e| *e).collect()
  }
 
  /// Get the current events deposited by the runtime.
  ///
  /// Should only be called if you know what you are doing and outside of the runtime block
  /// execution else it can have a large impact on the PoV size of a block.
- pub fn read_events_no_consensus() -> Vec<EventRecord<T::Event, T::Hash>> {
+ pub fn read_events_no_consensus() -> Vec<Box<EventRecord<T::Event, T::Hash>>> {
  Events::<T>::get()
  }