Make improvements

- Introduce ualarm() function
- Make rename() report EISEMPTY on Windows
- Always raise EINVAL upon open(O_RDONLY|O_TRUNC)
- Add macro so ./configure will detect SOCK_CLOEXEC
- Fix O_TRUNC without O_CREAT not working on Windows
- Let fcntl(F_SETFL) change O_APPEND status on Windows
- Make sure pwrite() / pread() report ESPIPE on sockets
- Raise ESPIPE on Windows when pwrite() is used on pipe
- Properly compute O_APPEND CreateFile() flags on Windows
- Don't require O_DIRECTORY to open directories on Windows
- Fix more instances of Windows reporting EISDIR and ENOTDIR
- Normalize EFTYPE and EMLINK to ELOOP on NetBSD and FreeBSD
- Make unlink() / rmdir() work on read-only files on Windows
- Validate UTF-8 on Windows paths to fix bug with overlong NUL
- Always print signal name to stderr when crashing due to SIG_DFL
- Fix Windows bug where denormalized paths >260 chars didn't work
- Block signals on BSDs when thread exits before trashing its own stack

libc/calls/pipe2.c

@@ -30,7 +30,8 @@
  * This function offers atomic operation on all supported platforms
  * except for XNU and RHEL5 where it's polyfilled.
  *
- * @params flags may contain `O_CLOEXEC`, `O_NONBLOCK`, and `O_DIRECT`
+ * @params flags may contain `O_CLOEXEC`, `O_NONBLOCK`, or the non-POSIX
+ *     packet mode flag `O_DIRECT`, which is `EINVAL` on MacOS / OpenBSD
  * @raise EINVAL if flags has invalid or unsupported bits
  * @raise EFAULT if `pipefd` doesn't point to valid memory
  * @raise EMFILE if process `RLIMIT_NOFILE` has been reached
@@ -41,7 +42,7 @@
  */
 int pipe2(int pipefd[hasatleast 2], int flags) {
   int rc;
-  if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT)) {
+  if (flags & ~(O_CLOEXEC | O_NONBLOCK | (O_DIRECT != -1u ? O_DIRECT : 0))) {
     return einval();
   } else if (!pipefd ||
              (IsAsan() && !__asan_is_valid(pipefd, sizeof(int) * 2))) {