From 76d58616d04d882ac0ef3ab784ca3d362e1a96df Mon Sep 17 00:00:00 2001
From: "Ben L. Titzer" <ben.titzer@gmail.com>
Date: Wed, 22 Jul 2026 17:10:29 -0400
Subject: [PATCH] Fix check for dropped elements and data in array.new_data

---
 src/engine/Instance.v3 | 6 ++++++
 src/engine/Runtime.v3  | 8 +++-----
 test/regress.failures  | 1 -
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/engine/Instance.v3 b/src/engine/Instance.v3
index 3040c3a90..dea08298f 100644
--- a/src/engine/Instance.v3
+++ b/src/engine/Instance.v3
@@ -147,7 +147,12 @@ class Instance(module: Module, imports: Array<Exportable>) {
 		var d: T;
 		return d;
 	}
+	def getData(data_index: int) -> Array<byte> {
+		if (dropped_data[data_index]) return EMPTY_BYTE_ARRAY;
+		return this.module.data[data_index].data;
+	}
 	def getElems(elem_index: int) -> Array<Value> {
+		if (dropped_elems[elem_index]) return Values.NONE;
 		var evals = this.elems[elem_index];
 		if (evals != null) return evals;
 		var edecl = module.elems[elem_index];
@@ -164,3 +169,4 @@ class Instance(module: Module, imports: Array<Exportable>) {
 		return evals;
 	}
 }
+def EMPTY_BYTE_ARRAY: Array<byte> = [];
diff --git a/src/engine/Runtime.v3 b/src/engine/Runtime.v3
index c37e92193..1050bcda3 100644
--- a/src/engine/Runtime.v3
+++ b/src/engine/Runtime.v3
@@ -111,11 +111,10 @@ component Runtime {
 	def ARRAY_NEW_DATA(stack: ExecStack, instance: Instance, array_index: u31, data_index: u31) -> Throwable {
 		var length = stack.popu();
 		var offset = stack.popu();
-		if (instance.dropped_data[data_index]) return stack.trap(TrapReason.MEMORY_OOB);
 		if (length > Execute.limits.max_array_length) return stack.trap(TrapReason.OOM);
 		var rtt = ArrayDecl.!(instance.heaptypes[array_index]);
-		var ddecl = instance.module.data[data_index];
-		var t = bytesToVals(rtt.elem_types[0], ddecl.data, offset, length);
+		var ddata = instance.getData(data_index);
+		var t = bytesToVals(rtt.elem_types[0], ddata, offset, length);
 		if (!t.0) return stack.trap(TrapReason.MEMORY_OOB);
 		stack.push(Value.Ref(HeapArray.new(rtt, t.1)));
 		return null;
@@ -123,7 +122,6 @@ component Runtime {
 	def ARRAY_NEW_ELEM(stack: ExecStack, instance: Instance, array_index: u31, elem_index: u31) -> Throwable {
 		var length = stack.popu();
 		var offset = stack.popu();
-		if (instance.dropped_elems[elem_index]) return stack.trap(TrapReason.MEMORY_OOB);
 		if (length > Execute.limits.max_array_length) return stack.trap(TrapReason.OOM);
 		var rtt = ArrayDecl.!(instance.heaptypes[array_index]);
 		var evals = instance.getElems(elem_index);
@@ -422,11 +420,11 @@ component Runtime {
 	}
 }
 def bytesToVals(storage: StorageType, data: Array<byte>, offset: u32, length: u32) -> (bool, Array<Value>) { // TODO: MaybeTrap
-	var vals = Array<Value>.new(int.!(length));
 	var start = ArrayUtil.boundsCheck(data, offset, length);
 	if (start < 0) return (false, null);
 	var limit = sizeOfStorage(storage) * length + offset;
 	if (limit > data.length) return (false, null);
+	var vals = Array<Value>.new(int.!(length));
 	var d = DataReader.new(data).reset(data, start, int.!(limit));
 	match (storage.pack) {
 		UNPACKED => {
diff --git a/test/regress.failures b/test/regress.failures
index 468c88a0d..0356b1366 100644
--- a/test/regress.failures
+++ b/test/regress.failures
@@ -1,4 +1,3 @@
 test/regress/ext:threads/atomic_wait32_0.bin.wast
 test/regress/ext:threads/atomic_wait64_0.bin.wast
-test/regress/ext:gc/zdrop_657.bin.wast
 test/regress/ext:gc/zcopy_656.bin.wast