chore: propagate changes from v0.19.x

Author: bobbinth

miden-crypto/src/merkle/smt/forest/mod.rs

@@ -207,7 +207,13 @@ impl SmtForest {
                 self.leaves.insert(leaf_hash, leaf);
             }
         }
-        self.roots.insert(new_root);
+        // Never register the empty tree root in self.roots, as it is always implicitly valid
+        // and the empty hash nodes are pre-populated infrastructure in the SmtStore.
+        // Adding it here would let `pop_smts` walk and destroy those nodes,
+        // corrupting the store for all future operations.
+        if new_root != *EmptySubtreeRoots::entry(SMT_DEPTH, 0) {
+            self.roots.insert(new_root);
+        }
 
         Ok(new_root)
     }

miden-crypto/src/merkle/smt/forest/tests.rs

@@ -313,3 +313,27 @@ fn test_removing_empty_smt_from_forest() {
     // Popping the empty root should be a no-op (no panic or error)
     forest.pop_smts(vec![empty_tree_root]);
 }
+
+#[test]
+fn test_empty_root_never_removed() -> Result<(), MerkleError> {
+    // Verify that the empty tree root is never registered in self.roots and that
+    // popping it does not corrupt the store.
+    let mut forest = SmtForest::new();
+    let empty_root = *EmptySubtreeRoots::entry(SMT_DEPTH, 0);
+    let key = Word::new([ZERO; WORD_SIZE]);
+    let value = Word::new([ONE; WORD_SIZE]);
+
+    // batch_insert with no entries returns the empty root — it must not be registered
+    let root = forest.batch_insert(empty_root, vec![])?;
+    assert_eq!(root, empty_root);
+
+    // Popping the empty root would corrupt the store if it were in self.roots.
+    forest.pop_smts(vec![empty_root]);
+
+    // The forest should still be fully functional
+    let new_root = forest.insert(empty_root, key, value)?;
+    let proof = forest.open(new_root, key)?;
+    assert!(proof.verify_presence(&key, &value, &new_root).is_ok());
+
+    Ok(())
+}

miden-crypto/src/merkle/smt/mod.rs

@@ -22,8 +22,8 @@ mod large;
 pub use full::concurrent::{SubtreeLeaf, build_subtree_for_bench};
 #[cfg(feature = "concurrent")]
 pub use large::{
-    LargeSmt, LargeSmtError, MemoryStorage, SmtStorage, StorageUpdateParts, StorageUpdates,
-    Subtree, SubtreeError,
+    LargeSmt, LargeSmtError, MemoryStorage, SmtStorage, StorageError, StorageUpdateParts,
+    StorageUpdates, Subtree, SubtreeError, SubtreeUpdate,
 };
 #[cfg(feature = "rocksdb")]
 pub use large::{RocksDbConfig, RocksDbStorage};