Make improvements

- Improve compatibility with Blink virtual machine
- Add non-POSIX APIs for joining threads and signal masks
- Never ever use anything except 32-bit integers for atomics
- Add some `#undef` statements to workaround `ctags` problems

libc/thread/pthread_tryjoin_np.c

@@ -0,0 +1,42 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/thread/thread2.h"
+
+/**
+ * Joins thread if it's already terminated.
+ *
+ * Multiple threads joining the same thread is undefined behavior. If a
+ * deferred or masked cancellation happens to the calling thread either
+ * before or during the waiting process then the target thread will not
+ * be joined. Calling pthread_join() on a non-joinable thread, e.g. one
+ * that's been detached, is undefined behavior. If a thread attempts to
+ * join itself, then the behavior is undefined.
+ *
+ * @param value_ptr if non-null will receive pthread_exit() argument
+ *     if the thread called pthread_exit(), or `PTHREAD_CANCELED` if
+ *     pthread_cancel() destroyed the thread instead
+ * @return 0 on success, or errno on error
+ * @raise ECANCELED if calling thread was cancelled in masked mode
+ * @cancellationpoint
+ * @returnserrno
+ * @threadsafe
+ */
+errno_t pthread_tryjoin_np(pthread_t thread, void **value_ptr) {
+  return pthread_timedjoin_np(thread, value_ptr, &timespec_zero);
+}