fix stack overflow in isAncestor recursion

beacon_chain/beacon_node_types.nim

@@ -2,6 +2,7 @@ import
   deques, tables, options,
   stew/[endians2], chronicles,
   spec/[datatypes, crypto, digest],
+  nimcrypto/utils,
   beacon_chain_db
 
 type
@@ -214,8 +215,9 @@ type
 proc shortLog*(v: AttachedValidator): string = shortLog(v.pubKey)
 
 chronicles.formatIt BlockSlot:
-  ($it.blck.root)[0..7] & ":" & $it.slot
+  mixin toHex
+  it.blck.root.data[0..3].toHex(true) & ":" & $it.slot
 
 chronicles.formatIt BlockRef:
-  ($it.root)[0..7] & ":" & $it.slot
-
+  mixin toHex
+  it.root.data[0..3].toHex(true) & ":" & $it.slot

beacon_chain/block_pool.nim

@@ -615,12 +615,22 @@ proc loadTailState*(pool: BlockPool): StateData =
   )
 
 func isAncestorOf*(a, b: BlockRef): bool =
-  if a == b:
-    true
-  elif a.slot >= b.slot or b.parent.isNil:
-    false
-  else:
-    a.isAncestorOf(b.parent)
+  var b = b
+  var depth = 0
+  const maxDepth = (100'i64 * 365 * 24 * 60 * 60 div SECONDS_PER_SLOT.int)
+  while true:
+    if a == b: return true
+
+    # for now, use an assert for block chain length since a chain this long
+    # indicates a circular reference here..
+    doAssert depth < maxDepth
+    depth += 1
+
+    if a.slot >= b.slot or b.parent.isNil:
+      return false
+
+    doAssert b.slot > b.parent.slot
+    b = b.parent
 
 proc delBlockAndState(pool: BlockPool, blockRoot: Eth2Digest) =
   if (let blk = pool.db.getBlock(blockRoot); blk.isSome):

beacon_chain/spec/digest.nim

@@ -33,10 +33,10 @@ type
 
 chronicles.formatIt Eth2Digest:
   mixin toHex
-  it.data.toHex(true)[0..7]
+  it.data[0..3].toHex(true)
 
 func shortLog*(x: Eth2Digest): string =
-  x.data.toHex(true)[0..7]
+  x.data[0..3].toHex(true)
 
 # TODO: expose an in-place digest function
 #       when hashing in loop or into a buffer

tests/test_block_pool.nim

@@ -94,3 +94,19 @@ suite "Block pool processing" & preset():
       hash_tree_root(state.data.data) == state.data.root
       pool2.get(b1Root).isSome()
       pool2.get(b2Root).isSome()
+
+  test "isAncestorOf sanity" & preset():
+    let
+      a = BlockRef(slot: Slot(1))
+      b = BlockRef(slot: Slot(2), parent: a)
+      c = BlockRef(slot: Slot(3), parent: b)
+
+    check:
+      a.isAncestorOf(a)
+      a.isAncestorOf(b)
+      a.isAncestorOf(c)
+      b.isAncestorOf(c)
+
+      not c.isAncestorOf(a)
+      not c.isAncestorOf(b)
+      not b.isAncestorOf(a)