Improve cancellations, randomness, and time

- Exhaustively document cancellation points
- Rename SIGCANCEL to SIGTHR just like BSDs
- Further improve POSIX thread cancellations
- Ensure asynchronous cancellations work correctly
- Elevate the quality of getrandom() and getentropy()
- Make futexes cancel correctly on OpenBSD 6.x and 7.x
- Add reboot.com and shutdown.com to examples directory
- Remove underscore prefix from awesome timespec_*() APIs
- Create assertions that help verify our cancellation points
- Remove bad timespec APIs (cmp generalizes eq/ne/gt/gte/lt/lte)

libc/intrin/getenv.c

@@ -34,10 +34,10 @@ char *getenv(const char *s) {
   if (!(p = environ)) return 0;
   e = _getenv(p, s);
 #if SYSDEBUG
-  if (!(s[0] == 'T' && s[1] == 'Z' && !s[2])) {
-    // TODO(jart): memoize TZ or something
-    STRACE("getenv(%#s) → %#s", s, e.s);
-  }
+  // if (!(s[0] == 'T' && s[1] == 'Z' && !s[2])) {
+  // TODO(jart): memoize TZ or something
+  STRACE("getenv(%#s) → %#s", s, e.s);
+  //}
 #endif
   return e.s;
 }

libc/intrin/ksignalnames.S

@@ -61,12 +61,12 @@ kSignalNames:
 	.e	SIGWINCH,"SIGWINCH"
 	.e	SIGIO,"SIGIO"
 	.e	SIGSYS,"SIGSYS"
-	.e	SIGINFO,"SIGINFO"
-	.e	SIGCANCEL,"SIGCANCEL"
+	.e	SIGPWR,"SIGPWR"
+	.e	SIGINFO,"SIGINFO"		# order matters
+	.e	SIGTHR,"SIGTHR"			# order matters
 	.e	SIGRTMAX,"SIGRTMAX"
 	.e	SIGRTMIN,"SIGRTMIN"
-	.e	SIGEMT,"SIGEMT"
-	.e	SIGPWR,"SIGPWR"
+	.e	SIGEMT,"SIGEMT"			# order matters
 	.long	MAGNUM_TERMINATOR
 	.endobj	kSignalNames,globl,hidden
 	.overrun

libc/intrin/pthread_key_create.c

@@ -29,6 +29,8 @@
  * key's value is nonzero. The key's value is set to zero before it gets
  * called. The ordering for multiple destructor calls is unspecified.
  *
+ * The result should be passed to pthread_key_delete() later.
+ *
  * @param key is set to the allocated key on success
  * @param dtor specifies an optional destructor callback
  * @return 0 on success, or errno on error

libc/intrin/pthread_setcancelstate.c

@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/blockcancel.internal.h"
 #include "libc/errno.h"
 #include "libc/thread/posixthread.internal.h"
 #include "libc/thread/thread.h"
@@ -76,3 +77,13 @@ errno_t pthread_setcancelstate(int state, int *oldstate) {
     return 0;
   }
 }
+
+int _pthread_block_cancellations(void) {
+  int oldstate;
+  pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
+  return oldstate;
+}
+
+void _pthread_allow_cancellations(int oldstate) {
+  pthread_setcancelstate(oldstate, 0);
+}

libc/intrin/sigisprecious.inc

@@ -1,4 +1,4 @@
 M(SIGKILL)
 M(SIGABRT)
 M(SIGSTOP)
-M(SIGCANCEL)
+M(SIGTHR)

libc/intrin/winerr.greg.c

@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #define ShouldUseMsabiAttribute() 1
+#include "libc/assert.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/nt/errors.h"
@@ -34,6 +35,7 @@ privileged int64_t __winerr(void) {
   errno_t e;
   if (IsWindows()) {
     e = __dos2errno(__imp_GetLastError());
+    _npassert(e > 0);
   } else {
     e = ENOSYS;
   }