Reland of [wasm] Enforce that function bodies end with the \"end\" opcode.

test/cctest/wasm/wasm-run-utils.h

Index: test/cctest/wasm/wasm-run-utils.h
diff --git a/test/cctest/wasm/wasm-run-utils.h b/test/cctest/wasm/wasm-run-utils.h
index 0ee7deb4fcf2615e2265c2f9aba138d74fae5c87..6b9a63f545ca1f28446e94da028e5db822977a8c 100644
--- a/test/cctest/wasm/wasm-run-utils.h
+++ b/test/cctest/wasm/wasm-run-utils.h
@@ -509,7 +509,18 @@
   uint32_t function_index() { return function_->func_index; }
 
   void Build(const byte* start, const byte* end) {
-    local_decls.Prepend(zone(), &start, &end);
+    size_t locals_size = local_decls.Size();
+    size_t total_size = end - start + locals_size + 1;
+    byte* buffer = static_cast<byte*>(zone()->New(total_size));
+    // Prepend the local decls to the code.
+    local_decls.Emit(buffer);
+    // Emit the code.
+    memcpy(buffer + locals_size, start, end - start);
+    // Append an extra end opcode.
+    buffer[total_size - 1] = kExprEnd;
+
+    start = buffer;
+    end = buffer + total_size;
 
     CHECK_GE(kMaxInt, end - start);
     int len = static_cast<int>(end - start);