--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/libuv/test/test-queue-foreach-delete.c	Wed Jan 14 19:39:52 2026 -0800
@@ -0,0 +1,205 @@
+/* Copyright The libuv project and 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>
+
+
+/*
+ * The idea behind the test is as follows.
+ * Certain handle types are stored in a queue internally.
+ * Extra care should be taken for removal of a handle from the queue while iterating over the queue.
+ * (i.e., uv__queue_remove() called within uv__queue_foreach())
+ * This usually happens when someone closes or stops a handle from within its callback.
+ * So we need to check that we haven't screwed the queue on close/stop.
+ * To do so we do the following (for each handle type):
+ *  1. Create and start 3 handles (#0, #1, and #2).
+ *
+ *     The queue after the start() calls:
+ *     ..=> [queue head] <=> [handle] <=> [handle #1] <=> [handle] <=..
+ *
+ *  2. Trigger handles to fire (for uv_idle_t, uv_prepare_t, and uv_check_t there is nothing to do).
+ *
+ *  3. In the callback for the first-executed handle (#0 or #2 depending on handle type)
+ *     stop the handle and the next one (#1).
+ *     (for uv_idle_t, uv_prepare_t, and uv_check_t callbacks are executed in the reverse order as they are start()'ed,
+ *     so callback for handle #2 will be called first)
+ *
+ *     The queue after the stop() calls:
+ *                                correct foreach "next"  |
+ *                                                       \/
+ *     ..=> [queue head] <==============================> [handle] <=..
+ *          [          ] <-  [handle] <=> [handle #1]  -> [      ]
+ *                                       /\
+ *                  wrong foreach "next"  |
+ *
+ *  4. The callback for handle #1 shouldn't be called because the handle #1 is stopped in the previous step.
+ *     However, if uv__queue_remove() is not handled properly within uv__queue_foreach(), the callback _will_
+ *     be called.
+ */
+
+static const unsigned first_handle_number_idle     = 2;
+static const unsigned first_handle_number_prepare  = 2;
+static const unsigned first_handle_number_check    = 2;
+#ifdef __linux__
+static const unsigned first_handle_number_fs_event = 0;
+#endif
+
+
+#define DEFINE_GLOBALS_AND_CBS(name, ...)                                     \
+  static uv_##name##_t (name)[3];                                             \
+  static unsigned name##_cb_calls[3];                                         \
+                                                                              \
+  static void name##2_cb(__VA_ARGS__) {                                       \
+    ASSERT_PTR_EQ(handle, &(name)[2]);                                        \
+    if (first_handle_number_##name == 2) {                                    \
+      uv_close((uv_handle_t*)&(name)[2], NULL);                               \
+      uv_close((uv_handle_t*)&(name)[1], NULL);                               \
+    }                                                                         \
+    name##_cb_calls[2]++;                                                     \
+  }                                                                           \
+                                                                              \
+  static void name##1_cb(__VA_ARGS__) {                                       \
+    ASSERT_PTR_EQ(handle, &(name)[1]);                                        \
+    ASSERT(0 && "Shouldn't be called" && (&name[0]));                         \
+  }                                                                           \
+                                                                              \
+  static void name##0_cb(__VA_ARGS__) {                                       \
+    ASSERT_PTR_EQ(handle, &(name)[0]);                                        \
+    if (first_handle_number_##name == 0) {                                    \
+      uv_close((uv_handle_t*)&(name)[0], NULL);                               \
+      uv_close((uv_handle_t*)&(name)[1], NULL);                               \
+    }                                                                         \
+    name##_cb_calls[0]++;                                                     \
+  }                                                                           \
+                                                                              \
+  static const uv_##name##_cb name##_cbs[] = {                                \
+    name##0_cb,                                                               \
+    name##1_cb,                                                               \
+    name##2_cb,                                                               \
+  };
+
+#define INIT_AND_START(name, loop)                                            \
+  do {                                                                        \
+    size_t i;                                                                 \
+    for (i = 0; i < ARRAY_SIZE(name); i++) {                                  \
+      int r;                                                                  \
+      r = uv_##name##_init((loop), &(name)[i]);                               \
+      ASSERT_OK(r);                                                           \
+                                                                              \
+      r = uv_##name##_start(&(name)[i], name##_cbs[i]);                       \
+      ASSERT_OK(r);                                                           \
+    }                                                                         \
+  } while (0)
+
+#define END_ASSERTS(name)                                                     \
+  do {                                                                        \
+    ASSERT_EQ(1, name##_cb_calls[0]);                                         \
+    ASSERT_OK(name##_cb_calls[1]);                                            \
+    ASSERT_EQ(1, name##_cb_calls[2]);                                         \
+  } while (0)
+
+DEFINE_GLOBALS_AND_CBS(idle, uv_idle_t* handle)
+DEFINE_GLOBALS_AND_CBS(prepare, uv_prepare_t* handle)
+DEFINE_GLOBALS_AND_CBS(check, uv_check_t* handle)
+
+#ifdef __linux__
+DEFINE_GLOBALS_AND_CBS(fs_event,
+                       uv_fs_event_t* handle,
+                       const char* filename,
+                       int events,
+                       int status)
+
+static const char watched_dir[] = ".";
+static uv_timer_t timer;
+static unsigned helper_timer_cb_calls;
+
+
+static void init_and_start_fs_events(uv_loop_t* loop) {
+  size_t i;
+  for (i = 0; i < ARRAY_SIZE(fs_event); i++) {
+    int r;
+    r = uv_fs_event_init(loop, &fs_event[i]);
+    ASSERT_OK(r);
+
+    r = uv_fs_event_start(&fs_event[i],
+                          (uv_fs_event_cb)fs_event_cbs[i],
+                          watched_dir,
+                          0);
+    ASSERT_OK(r);
+  }
+}
+
+static void helper_timer_cb(uv_timer_t* thandle) {
+  int r;
+  uv_fs_t fs_req;
+
+  /* fire all fs_events */
+  r = uv_fs_utime(thandle->loop, &fs_req, watched_dir, 0, 0, NULL);
+  ASSERT_OK(r);
+  ASSERT_OK(fs_req.result);
+  ASSERT_EQ(fs_req.fs_type, UV_FS_UTIME);
+  ASSERT_OK(strcmp(fs_req.path, watched_dir));
+  uv_fs_req_cleanup(&fs_req);
+
+  helper_timer_cb_calls++;
+}
+#endif
+
+
+TEST_IMPL(queue_foreach_delete) {
+  uv_loop_t* loop;
+  int r;
+
+  loop = uv_default_loop();
+
+  INIT_AND_START(idle,    loop);
+  INIT_AND_START(prepare, loop);
+  INIT_AND_START(check,   loop);
+
+#ifdef __linux__
+  init_and_start_fs_events(loop);
+
+  /* helper timer to trigger async and fs_event callbacks */
+  r = uv_timer_init(loop, &timer);
+  ASSERT_OK(r);
+
+  r = uv_timer_start(&timer, helper_timer_cb, 0, 0);
+  ASSERT_OK(r);
+#endif
+
+  r = uv_run(loop, UV_RUN_NOWAIT);
+  ASSERT_EQ(1, r);
+
+  END_ASSERTS(idle);
+  END_ASSERTS(prepare);
+  END_ASSERTS(check);
+
+#ifdef __linux__
+  ASSERT_EQ(1, helper_timer_cb_calls);
+#endif
+
+  MAKE_VALGRIND_HAPPY(loop);
+
+  return 0;
+}