--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/libuv/test/test-fs-open-flags.c	Wed Jan 14 19:39:52 2026 -0800
@@ -0,0 +1,435 @@
+/* Copyright libuv project 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.
+ */
+
+#ifdef _WIN32
+
+#include "uv.h"
+#include "task.h"
+
+#if defined(__unix__) || defined(__POSIX__) || \
+    defined(__APPLE__) || defined(__sun) || \
+    defined(_AIX) || defined(__MVS__) || \
+    defined(__HAIKU__)
+# include <unistd.h> /* unlink, rmdir */
+#else
+# include <direct.h>
+# define rmdir _rmdir
+# define unlink _unlink
+#endif
+
+static int flags;
+
+static uv_fs_t close_req;
+static uv_fs_t mkdir_req;
+static uv_fs_t open_req;
+static uv_fs_t read_req;
+static uv_fs_t rmdir_req;
+static uv_fs_t unlink_req;
+static uv_fs_t write_req;
+
+static char buf[32];
+static uv_buf_t iov;
+
+/* Opening the same file multiple times quickly can cause uv_fs_open to fail
+ * with EBUSY, so append an identifier to the file name for each operation */
+static int sid = 0;
+
+#define FILE_NAME_SIZE 128
+static char absent_file[FILE_NAME_SIZE];
+static char empty_file[FILE_NAME_SIZE];
+static char dummy_file[FILE_NAME_SIZE];
+static char empty_dir[] = "empty_dir";
+
+static void setup(void) {
+  int r;
+
+  /* empty_dir */
+  r = uv_fs_rmdir(NULL, &rmdir_req, empty_dir, NULL);
+  ASSERT(r == 0 || r == UV_ENOENT);
+  ASSERT(rmdir_req.result == 0 || rmdir_req.result == UV_ENOENT);
+  uv_fs_req_cleanup(&rmdir_req);
+
+  r = uv_fs_mkdir(NULL, &mkdir_req, empty_dir, 0755, NULL);
+  ASSERT_OK(r);
+  ASSERT_OK(mkdir_req.result);
+  uv_fs_req_cleanup(&mkdir_req);
+}
+
+static void refresh(void) {
+  int r;
+
+  /* absent_file */
+  sprintf(absent_file, "test_file_%d", sid++);
+
+  r = uv_fs_unlink(NULL, &unlink_req, absent_file, NULL);
+  ASSERT(r == 0 || r == UV_ENOENT);
+  ASSERT(unlink_req.result == 0 || unlink_req.result == UV_ENOENT);
+  uv_fs_req_cleanup(&unlink_req);
+
+  /* empty_file */
+  sprintf(empty_file, "test_file_%d", sid++);
+
+  r = uv_fs_open(NULL, &open_req, empty_file,
+    UV_FS_O_TRUNC | UV_FS_O_CREAT | UV_FS_O_WRONLY, S_IWUSR | S_IRUSR, NULL);
+  ASSERT_GE(r, 0);
+  ASSERT_GE(open_req.result, 0);
+  uv_fs_req_cleanup(&open_req);
+
+  r = uv_fs_close(NULL, &close_req, open_req.result, NULL);
+  ASSERT_OK(r);
+  ASSERT_OK(close_req.result);
+  uv_fs_req_cleanup(&close_req);
+
+  /* dummy_file */
+  sprintf(dummy_file, "test_file_%d", sid++);
+
+  r = uv_fs_open(NULL, &open_req, dummy_file,
+    UV_FS_O_TRUNC | UV_FS_O_CREAT | UV_FS_O_WRONLY, S_IWUSR | S_IRUSR, NULL);
+  ASSERT_GE(r, 0);
+  ASSERT_GE(open_req.result, 0);
+  uv_fs_req_cleanup(&open_req);
+
+  iov = uv_buf_init("a", 1);
+  r = uv_fs_write(NULL, &write_req, open_req.result, &iov, 1, -1, NULL);
+  ASSERT_EQ(1, r);
+  ASSERT_EQ(1, write_req.result);
+  uv_fs_req_cleanup(&write_req);
+
+  r = uv_fs_close(NULL, &close_req, open_req.result, NULL);
+  ASSERT_OK(r);
+  ASSERT_OK(close_req.result);
+  uv_fs_req_cleanup(&close_req);
+}
+
+static void cleanup(void) {
+  unlink(absent_file);
+  unlink(empty_file);
+  unlink(dummy_file);
+}
+
+static void openFail(char *file, int error) {
+  int r;
+
+  refresh();
+
+  r = uv_fs_open(NULL, &open_req, file, flags, S_IWUSR | S_IRUSR, NULL);
+  ASSERT_EQ(r, error);
+  ASSERT_EQ(open_req.result, error);
+  uv_fs_req_cleanup(&open_req);
+
+  /* Ensure the first call does not create the file */
+  r = uv_fs_open(NULL, &open_req, file, flags, S_IWUSR | S_IRUSR, NULL);
+  ASSERT_EQ(r, error);
+  ASSERT_EQ(open_req.result, error);
+  uv_fs_req_cleanup(&open_req);
+
+  cleanup();
+}
+
+static void refreshOpen(char *file) {
+  int r;
+
+  refresh();
+
+  r = uv_fs_open(NULL, &open_req, file, flags, S_IWUSR | S_IRUSR, NULL);
+  ASSERT_GE(r, 0);
+  ASSERT_GE(open_req.result, 0);
+  uv_fs_req_cleanup(&open_req);
+}
+
+static void writeExpect(char *file, char *expected, int size) {
+  int r;
+
+  refreshOpen(file);
+
+  iov = uv_buf_init("b", 1);
+  r = uv_fs_write(NULL, &write_req, open_req.result, &iov, 1, -1, NULL);
+  ASSERT_EQ(1, r);
+  ASSERT_EQ(1, write_req.result);
+  uv_fs_req_cleanup(&write_req);
+
+  iov = uv_buf_init("c", 1);
+  r = uv_fs_write(NULL, &write_req, open_req.result, &iov, 1, -1, NULL);
+  ASSERT_EQ(1, r);
+  ASSERT_EQ(1, write_req.result);
+  uv_fs_req_cleanup(&write_req);
+
+  r = uv_fs_close(NULL, &close_req, open_req.result, NULL);
+  ASSERT_OK(r);
+  ASSERT_OK(close_req.result);
+  uv_fs_req_cleanup(&close_req);
+
+  /* Check contents */
+  r = uv_fs_open(NULL, &open_req, file, UV_FS_O_RDONLY, S_IWUSR | S_IRUSR, NULL);
+  ASSERT_GE(r, 0);
+  ASSERT_GE(open_req.result, 0);
+  uv_fs_req_cleanup(&open_req);
+
+  iov = uv_buf_init(buf, sizeof(buf));
+  r = uv_fs_read(NULL, &read_req, open_req.result, &iov, 1, -1, NULL);
+  ASSERT_EQ(r, size);
+  ASSERT_EQ(read_req.result, size);
+  ASSERT_OK(strncmp(buf, expected, size));
+  uv_fs_req_cleanup(&read_req);
+
+  r = uv_fs_close(NULL, &close_req, open_req.result, NULL);
+  ASSERT_OK(r);
+  ASSERT_OK(close_req.result);
+  uv_fs_req_cleanup(&close_req);
+
+  cleanup();
+}
+
+static void writeFail(char *file, int error) {
+  int r;
+
+  refreshOpen(file);
+
+  iov = uv_buf_init("z", 1);
+  r = uv_fs_write(NULL, &write_req, open_req.result, &iov, 1, -1, NULL);
+  ASSERT_EQ(r, error);
+  ASSERT_EQ(write_req.result, error);
+  uv_fs_req_cleanup(&write_req);
+
+  iov = uv_buf_init("z", 1);
+  r = uv_fs_write(NULL, &write_req, open_req.result, &iov, 1, -1, NULL);
+  ASSERT_EQ(r, error);
+  ASSERT_EQ(write_req.result, error);
+  uv_fs_req_cleanup(&write_req);
+
+  r = uv_fs_close(NULL, &close_req, open_req.result, NULL);
+  ASSERT_OK(r);
+  ASSERT_OK(close_req.result);
+  uv_fs_req_cleanup(&close_req);
+
+  cleanup();
+}
+
+static void readExpect(char *file, char *expected, int size) {
+  int r;
+
+  refreshOpen(file);
+
+  iov = uv_buf_init(buf, sizeof(buf));
+  r = uv_fs_read(NULL, &read_req, open_req.result, &iov, 1, -1, NULL);
+  ASSERT_EQ(r, size);
+  ASSERT_EQ(read_req.result, size);
+  ASSERT_OK(strncmp(buf, expected, size));
+  uv_fs_req_cleanup(&read_req);
+
+  r = uv_fs_close(NULL, &close_req, open_req.result, NULL);
+  ASSERT_OK(r);
+  ASSERT_OK(close_req.result);
+  uv_fs_req_cleanup(&close_req);
+
+  cleanup();
+}
+
+static void readFail(char *file, int error) {
+  int r;
+
+  refreshOpen(file);
+
+  iov = uv_buf_init(buf, sizeof(buf));
+  r = uv_fs_read(NULL, &read_req, open_req.result, &iov, 1, -1, NULL);
+  ASSERT_EQ(r, error);
+  ASSERT_EQ(read_req.result, error);
+  uv_fs_req_cleanup(&read_req);
+
+  iov = uv_buf_init(buf, sizeof(buf));
+  r = uv_fs_read(NULL, &read_req, open_req.result, &iov, 1, -1, NULL);
+  ASSERT_EQ(r, error);
+  ASSERT_EQ(read_req.result, error);
+  uv_fs_req_cleanup(&read_req);
+
+  r = uv_fs_close(NULL, &close_req, open_req.result, NULL);
+  ASSERT_OK(r);
+  ASSERT_OK(close_req.result);
+  uv_fs_req_cleanup(&close_req);
+
+  cleanup();
+}
+
+static void fs_open_flags(int add_flags) {
+  /* Follow the order from
+   * https://github.com/nodejs/node/blob/1a96abe849/lib/internal/fs/utils.js#L329-L354
+   */
+
+  /* r */
+  flags = add_flags | UV_FS_O_RDONLY;
+  openFail(absent_file, UV_ENOENT);
+  writeFail(empty_file, UV_EBADF);
+  readExpect(empty_file, "", 0);
+  writeFail(dummy_file, UV_EBADF);
+  readExpect(dummy_file, "a", 1);
+  writeFail(empty_dir, UV_EBADF);
+  readFail(empty_dir, UV_EISDIR);
+
+  /* rs */
+  flags = add_flags | UV_FS_O_RDONLY | UV_FS_O_SYNC;
+  openFail(absent_file, UV_ENOENT);
+  writeFail(empty_file, UV_EBADF);
+  readExpect(empty_file, "", 0);
+  writeFail(dummy_file, UV_EBADF);
+  readExpect(dummy_file, "a", 1);
+  writeFail(empty_dir, UV_EBADF);
+  readFail(empty_dir, UV_EISDIR);
+
+  /* r+ */
+  flags = add_flags | UV_FS_O_RDWR;
+  openFail(absent_file, UV_ENOENT);
+  writeExpect(empty_file, "bc", 2);
+  readExpect(empty_file, "", 0);
+  writeExpect(dummy_file, "bc", 2);
+  readExpect(dummy_file, "a", 1);
+  writeFail(empty_dir, UV_EISDIR);
+  readFail(empty_dir, UV_EISDIR);
+
+  /* rs+ */
+  flags = add_flags | UV_FS_O_RDWR | UV_FS_O_SYNC;
+  openFail(absent_file, UV_ENOENT);
+  writeExpect(empty_file, "bc", 2);
+  readExpect(empty_file, "", 0);
+  writeExpect(dummy_file, "bc", 2);
+  readExpect(dummy_file, "a", 1);
+  writeFail(empty_dir, UV_EISDIR);
+  readFail(empty_dir, UV_EISDIR);
+
+  /* w */
+  flags = add_flags | UV_FS_O_TRUNC | UV_FS_O_CREAT | UV_FS_O_WRONLY;
+  writeExpect(absent_file, "bc", 2);
+  readFail(absent_file, UV_EBADF);
+  writeExpect(empty_file, "bc", 2);
+  readFail(empty_file, UV_EBADF);
+  writeExpect(dummy_file, "bc", 2);
+  readFail(dummy_file, UV_EBADF);
+  openFail(empty_dir, UV_EISDIR);
+
+  /* wx */
+  flags = add_flags | UV_FS_O_TRUNC | UV_FS_O_CREAT | UV_FS_O_WRONLY |
+    UV_FS_O_EXCL;
+  writeExpect(absent_file, "bc", 2);
+  readFail(absent_file, UV_EBADF);
+  openFail(empty_file, UV_EEXIST);
+  openFail(dummy_file, UV_EEXIST);
+  openFail(empty_dir, UV_EEXIST);
+
+  /* w+ */
+  flags = add_flags | UV_FS_O_TRUNC | UV_FS_O_CREAT | UV_FS_O_RDWR;
+  writeExpect(absent_file, "bc", 2);
+  readExpect(absent_file, "", 0);
+  writeExpect(empty_file, "bc", 2);
+  readExpect(empty_file, "", 0);
+  writeExpect(dummy_file, "bc", 2);
+  readExpect(dummy_file, "", 0);
+  openFail(empty_dir, UV_EISDIR);
+
+  /* wx+ */
+  flags = add_flags | UV_FS_O_TRUNC | UV_FS_O_CREAT | UV_FS_O_RDWR |
+    UV_FS_O_EXCL;
+  writeExpect(absent_file, "bc", 2);
+  readExpect(absent_file, "", 0);
+  openFail(empty_file, UV_EEXIST);
+  openFail(dummy_file, UV_EEXIST);
+  openFail(empty_dir, UV_EEXIST);
+
+  /* a */
+  flags = add_flags | UV_FS_O_APPEND | UV_FS_O_CREAT | UV_FS_O_WRONLY;
+  writeExpect(absent_file, "bc", 2);
+  readFail(absent_file, UV_EBADF);
+  writeExpect(empty_file, "bc", 2);
+  readFail(empty_file, UV_EBADF);
+  writeExpect(dummy_file, "abc", 3);
+  readFail(dummy_file, UV_EBADF);
+  writeFail(empty_dir, UV_EISDIR);
+  readFail(empty_dir, UV_EBADF);
+
+  /* ax */
+  flags = add_flags | UV_FS_O_APPEND | UV_FS_O_CREAT | UV_FS_O_WRONLY |
+    UV_FS_O_EXCL;
+  writeExpect(absent_file, "bc", 2);
+  readFail(absent_file, UV_EBADF);
+  openFail(empty_file, UV_EEXIST);
+  openFail(dummy_file, UV_EEXIST);
+  openFail(empty_dir, UV_EEXIST);
+
+  /* as */
+  flags = add_flags | UV_FS_O_APPEND | UV_FS_O_CREAT | UV_FS_O_WRONLY |
+    UV_FS_O_SYNC;
+  writeExpect(absent_file, "bc", 2);
+  readFail(absent_file, UV_EBADF);
+  writeExpect(empty_file, "bc", 2);
+  readFail(empty_file, UV_EBADF);
+  writeExpect(dummy_file, "abc", 3);
+  readFail(dummy_file, UV_EBADF);
+  writeFail(empty_dir, UV_EISDIR);
+  readFail(empty_dir, UV_EBADF);
+
+  /* a+ */
+  flags = add_flags | UV_FS_O_APPEND | UV_FS_O_CREAT | UV_FS_O_RDWR;
+  writeExpect(absent_file, "bc", 2);
+  readExpect(absent_file, "", 0);
+  writeExpect(empty_file, "bc", 2);
+  readExpect(empty_file, "", 0);
+  writeExpect(dummy_file, "abc", 3);
+  readExpect(dummy_file, "a", 1);
+  writeFail(empty_dir, UV_EISDIR);
+  readFail(empty_dir, UV_EISDIR);
+
+  /* ax+ */
+  flags = add_flags | UV_FS_O_APPEND | UV_FS_O_CREAT | UV_FS_O_RDWR |
+    UV_FS_O_EXCL;
+  writeExpect(absent_file, "bc", 2);
+  readExpect(absent_file, "", 0);
+  openFail(empty_file, UV_EEXIST);
+  openFail(dummy_file, UV_EEXIST);
+  openFail(empty_dir, UV_EEXIST);
+
+  /* as+ */
+  flags = add_flags | UV_FS_O_APPEND | UV_FS_O_CREAT | UV_FS_O_RDWR |
+    UV_FS_O_SYNC;
+  writeExpect(absent_file, "bc", 2);
+  readExpect(absent_file, "", 0);
+  writeExpect(empty_file, "bc", 2);
+  readExpect(empty_file, "", 0);
+  writeExpect(dummy_file, "abc", 3);
+  readExpect(dummy_file, "a", 1);
+  writeFail(empty_dir, UV_EISDIR);
+  readFail(empty_dir, UV_EISDIR);
+}
+TEST_IMPL(fs_open_flags) {
+  setup();
+
+  fs_open_flags(0);
+  fs_open_flags(UV_FS_O_FILEMAP);
+
+  /* Cleanup. */
+  rmdir(empty_dir);
+
+  MAKE_VALGRIND_HAPPY(uv_default_loop());
+  return 0;
+}
+
+#else
+
+typedef int file_has_no_tests;  /* ISO C forbids an empty translation unit. */
+
+#endif  /* ifndef _WIN32 */