Change sleep_for, sleep_until, and the condition_variable timed wait

functions to protect against duration and time_point overflow.  Since
we're about to wait anyway, we can afford to spend a few more cycles on
this checking.  I purposefully did not treat the timed try_locks with
overflow checking.  This fixes
http://llvm.org/bugs/show_bug.cgi?id=13721 .  I'm unsure if the standard
needs clarification in this area, or if this is simply QOI.  The
<chrono> facilities were never intended to overflow check, but just to
not overflow if durations stayed within +/- 292 years.

llvm-svn: 162925

1 files changed, 14 insertions, 4 deletions

diff --git a/libcxx/include/thread b/libcxx/include/thread
index d81e8537888..94e7ab6c54c 100644
--- a/libcxx/include/thread
+++ b/libcxx/include/thread
@@ -410,10 +410,20 @@ void
 sleep_for(const chrono::duration<_Rep, _Period>& __d)
 {
     using namespace chrono;
-    nanoseconds __ns = duration_cast<nanoseconds>(__d);
-    if (__ns < __d)
-        ++__ns;
-    sleep_for(__ns);
+    if (__d > duration<_Rep, _Period>::zero())
+    {
+        _LIBCPP_CONSTEXPR duration<long double> _Max = nanoseconds::max();
+        nanoseconds __ns;
+        if (__d < _Max)
+        {
+            __ns = duration_cast<nanoseconds>(__d);
+            if (__ns < __d)
+                ++__ns;
+        }
+        else
+            __ns = nanoseconds::max();
+        sleep_for(__ns);
+    }
 }
 
 template <class _Clock, class _Duration>