Make improvements

- Clean up sigaction() code
- Add a port scanner example
- Introduce a ParseCidr() API
- Clean up our futex abstraction code
- Fix a harmless integer overflow in ParseIp()
- Use kernel semaphores on NetBSD to make threads much faster

libc/intrin/describetimespec.c

@@ -21,6 +21,7 @@
 #include "libc/intrin/asan.internal.h"
 #include "libc/intrin/describeflags.internal.h"
 #include "libc/intrin/kprintf.h"
+#include "libc/str/str.h"
 
 const char *(DescribeTimespec)(char buf[45], int rc,
                                const struct timespec *ts) {
@@ -30,7 +31,11 @@ const char *(DescribeTimespec)(char buf[45], int rc,
       (IsAsan() && !__asan_is_valid(ts, sizeof(*ts)))) {
     ksnprintf(buf, 45, "%p", ts);
   } else {
-    ksnprintf(buf, 45, "{%ld, %ld}", ts->tv_sec, ts->tv_nsec);
+    if (!memcmp(ts, &timespec_max, sizeof(*ts))) {
+      strcpy(buf, "timespec_max");
+    } else {
+      ksnprintf(buf, 45, "{%ld, %ld}", ts->tv_sec, ts->tv_nsec);
+    }
   }
   return buf;
 }

libc/intrin/gettid.c

@@ -20,6 +20,7 @@
 #include "libc/calls/state.internal.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/intrin/atomic.h"
+#include "libc/intrin/likely.h"
 #include "libc/thread/tls.h"
 
 /**
@@ -36,9 +37,9 @@
  */
 int gettid(void) {
   int tid;
-  if (__tls_enabled && !__vforked) {
-    tid = atomic_load_explicit(&__get_tls()->tib_tid, memory_order_relaxed);
-    if (tid > 0) {
+  if (VERY_LIKELY(__tls_enabled && !__vforked)) {
+    tid = atomic_load_explicit(&__get_tls()->tib_tid, memory_order_acquire);
+    if (VERY_LIKELY(tid > 0)) {
       return tid;
     }
   }