--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/libuv/test/test-async-null-cb.c	Wed Jan 14 19:39:52 2026 -0800
@@ -0,0 +1,64 @@
+/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "uv.h"
+#include "task.h"
+#include <string.h>
+
+static uv_async_t async_handle;
+static uv_check_t check_handle;
+static int check_cb_called;
+static uv_thread_t thread;
+
+
+static void thread_cb(void* dummy) {
+  (void) &dummy;
+  uv_async_send(&async_handle);
+}
+
+
+static void check_cb(uv_check_t* handle) {
+  ASSERT_OK(check_cb_called);
+  uv_close((uv_handle_t*) &async_handle, NULL);
+  uv_close((uv_handle_t*) &check_handle, NULL);
+  check_cb_called++;
+}
+
+
+TEST_IMPL(async_null_cb) {
+  /*
+   * Fill async_handle with garbage values.
+   * uv_async_init() should properly initialize struct fields regardless of
+   * initial values.
+   * This is added to verify paddings between fields do not affect behavior.
+   */
+  memset(&async_handle, 0xff, sizeof(async_handle));
+
+  ASSERT_OK(uv_async_init(uv_default_loop(), &async_handle, NULL));
+  ASSERT_OK(uv_check_init(uv_default_loop(), &check_handle));
+  ASSERT_OK(uv_check_start(&check_handle, check_cb));
+  ASSERT_OK(uv_thread_create(&thread, thread_cb, NULL));
+  ASSERT_OK(uv_run(uv_default_loop(), UV_RUN_DEFAULT));
+  ASSERT_OK(uv_thread_join(&thread));
+  ASSERT_EQ(1, check_cb_called);
+  MAKE_VALGRIND_HAPPY(uv_default_loop());
+  return 0;
+}