fix stackoverflow in PTCDuties registration by using closure iterators

Author: Tomi-3-0

beacon_chain/consensus_object_pools/spec_cache.nim

@@ -325,18 +325,3 @@ func is_aggregator*(shufflingRef: ShufflingRef, slot: Slot,
   let
     committee_len = get_beacon_committee_len(shufflingRef, slot, index)
   return is_aggregator(committee_len, slot_signature)
-
-# https://github.com/ethereum/consensus-specs/blob/v1.6.1/specs/gloas/validator.md#payload-timeliness-committee
-iterator get_ptc_assignment*(
-    state: gloas.BeaconState, epoch: Epoch,
-    validator_indices: HashSet[ValidatorIndex]):
-    tuple[slot: Slot, validator_index: ValidatorIndex] =
-  let next_epoch = state.get_current_epoch + 1
-  doAssert epoch <= next_epoch
-
-  var cache = StateCache()
-
-  for slot in epoch.slots():
-    for validator_index in get_ptc(state, slot, cache):
-      if validator_index in validator_indices:
-        yield(slot, validator_index)

beacon_chain/spec/beaconstate.nim

@@ -2764,7 +2764,7 @@ func can_advance_slots*(
 
 # https://github.com/ethereum/consensus-specs/blob/v1.6.0-alpha.6/specs/gloas/beacon-chain.md#new-get_ptc
 iterator get_ptc*(state: gloas.BeaconState, slot: Slot, cache: var StateCache):
-    ValidatorIndex =
+    ValidatorIndex {.closure.} =
   ## Get the payload timeliness committee for the given ``slot``
   let epoch = slot.epoch()
   var buffer {.noinit.}: array[40, byte]

beacon_chain/validators/beacon_validators.nim

@@ -1290,15 +1290,17 @@ proc registerPTCDuties(node: BeaconNode, epoch: Epoch) =
 
   withState(node.dag.headState):
     when consensusFork >= ConsensusFork.Gloas:
-      for (slot, validator_index) in get_ptc_assignment(
-          forkyState.data, epoch, validatorIndices):
-
-        node.consensusManager[].actionTracker.registerPTCDuty(
-          slot, validator_index)
-
-        debug "PTC duty registered",
-          slot = slot,
-          epoch = epoch
+      var cache = new StateCache
+      
+      for slot in epoch.slots():
+        for validator_index in get_ptc(forkyState.data, slot, cache[]):
+          if validator_index in validatorIndices:
+            node.consensusManager[].actionTracker.registerPTCDuty(
+              slot, validator_index)
+            
+            debug "PTC duty registered",
+              slot = slot,
+              epoch = epoch
 
 proc registerDuties*(node: BeaconNode, wallSlot: Slot) {.async: (raises: [CancelledError]).} =
   ## Register upcoming duties of attached validators with the duty tracker