Add *NSYNC unit test suite

This change also fixes the clock_nanosleep() api and polyfills futexes
on Windows, Mac, and NetBSD using exponential backoff.

libc/calls/clock_nanosleep.c

@@ -17,11 +17,13 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/asan.internal.h"
+#include "libc/calls/state.internal.h"
 #include "libc/calls/struct/timespec.h"
 #include "libc/calls/struct/timespec.internal.h"
 #include "libc/calls/struct/timeval.h"
 #include "libc/calls/struct/timeval.internal.h"
 #include "libc/dce.h"
+#include "libc/errno.h"
 #include "libc/intrin/describeflags.internal.h"
 #include "libc/intrin/strace.internal.h"
 #include "libc/sysv/consts/clock.h"
@@ -69,7 +71,7 @@
  *     (1) it's non-null; (2) `flags` is 0; and (3) -1 w/ `EINTR` is
  *     returned; if this function returns 0 then `rem` is undefined;
  *     if flags is `TIMER_ABSTIME` then `rem` is ignored
- * @return 0 on success, or -1 w/ errno
+ * @return 0 on success, or errno on error
  * @raise EINTR when a signal got delivered while we were waiting
  * @raise ENOTSUP if `clock` is known but we can't use it here
  * @raise EINVAL if `clock` is unknown to current platform
@@ -77,11 +79,12 @@
  * @raise EINVAL if `req->tv_nsec ∉ [0,1000000000)`
  * @raise EFAULT if bad memory was passed
  * @raise ENOSYS on bare metal
+ * @returnserrno
  * @norestart
  */
-int clock_nanosleep(int clock, int flags, const struct timespec *req,
-                    struct timespec *rem) {
-  int rc;
+errno_t clock_nanosleep(int clock, int flags, const struct timespec *req,
+                        struct timespec *rem) {
+  int rc, e = errno;
 
   if (!req || (IsAsan() && (!__asan_is_valid_timespec(req) ||
                             (rem && !__asan_is_valid_timespec(rem))))) {
@@ -103,9 +106,18 @@ int clock_nanosleep(int clock, int flags, const struct timespec *req,
     rc = sys_clock_nanosleep_nt(clock, flags, req, rem);
   }
 
-  STRACE("clock_nanosleep(%s, %s, %s, [%s]) → %d% m", DescribeClockName(clock),
-         DescribeSleepFlags(flags), flags, DescribeTimespec(0, req),
-         DescribeTimespec(rc, rem), rc);
+  if (rc == -1) {
+    rc = errno;
+    errno = e;
+  }
+
+#if SYSDEBUG
+  if (!__time_critical) {
+    STRACE("clock_nanosleep(%s, %s, %s, [%s]) → %s", DescribeClockName(clock),
+           DescribeSleepFlags(flags), DescribeTimespec(0, req),
+           DescribeTimespec(rc, rem), DescribeErrnoResult(rc));
+  }
+#endif
 
   return rc;
 }

libc/calls/nanosleep.c

@@ -21,11 +21,14 @@
 #include "libc/calls/state.internal.h"
 #include "libc/calls/struct/timespec.internal.h"
 #include "libc/dce.h"
+#include "libc/errno.h"
 #include "libc/intrin/describeflags.internal.h"
 #include "libc/intrin/strace.internal.h"
 #include "libc/sysv/consts/clock.h"
 #include "libc/sysv/errfuns.h"
 
+// TODO(jart): Just delegate to clock_nanosleep()
+
 /**
  * Sleeps for relative amount of time.
  *
@@ -49,9 +52,10 @@ int nanosleep(const struct timespec *req, struct timespec *rem) {
   } else if (req->tv_sec < 0 ||
              !(0 <= req->tv_nsec && req->tv_nsec <= 999999999)) {
     rc = einval();
-  } else if (IsLinux()) {
+  } else if (IsLinux() || IsFreebsd() || IsNetbsd()) {
     rc = sys_clock_nanosleep(CLOCK_REALTIME, 0, req, rem);
-  } else if (IsOpenbsd() || IsFreebsd() || IsNetbsd()) {
+    if (rc > 0) errno = rc, rc = -1;
+  } else if (IsOpenbsd()) {
     rc = sys_nanosleep(req, rem);
   } else if (IsXnu()) {
     rc = sys_nanosleep_xnu(req, rem);

libc/calls/posix_fadvise.c

@@ -41,6 +41,8 @@ int sys_fadvise_netbsd(int, int, int64_t, int64_t, int) asm("sys_fadvise");
  * @raise EINVAL if `advice` is invalid or `len` is huge
  * @raise ESPIPE if `fd` refers to a pipe
  * @raise ENOSYS on XNU and OpenBSD
+ * @returnserrno
+ * @threadsafe
  */
 errno_t posix_fadvise(int fd, uint64_t offset, uint64_t len, int advice) {
   int rc, e = errno;

libc/calls/posix_madvise.c

@@ -17,7 +17,21 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
+#include "libc/errno.h"
 
-int posix_madvise(void *addr, uint64_t len, int advice) {
-  return madvise(addr, len, advice);
+/**
+ * Advises kernel about memory intentions, the POSIX way.
+ *
+ * @return 0 on success, or errno on error
+ * @returnserrno
+ * @threadsafe
+ */
+errno_t posix_madvise(void *addr, uint64_t len, int advice) {
+  int rc, e = errno;
+  rc = madvise(addr, len, advice);
+  if (rc == -1) {
+    rc = errno;
+    errno = e;
+  }
+  return rc;
 }