Fixes: prevent compiler reporting UB, hazptr_array move operator, empty array test

[folly.git] / folly / experimental / EventCount.h

diff --git a/folly/experimental/EventCount.h b/folly/experimental/EventCount.h
index 43c27b7c50a078e3065e82a38308aae0946cd20e..f2f806cb0bac7de5228c757cfb33b2fa186d3dc2 100644 (file)
--- a/folly/experimental/EventCount.h
+++ b/folly/experimental/EventCount.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2015 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,33 +14,23 @@
  * limitations under the License.
  */
 
-#ifndef FOLLY_EXPERIMENTAL_EVENTCOUNT_H_
-#define FOLLY_EXPERIMENTAL_EVENTCOUNT_H_
+#pragma once
 
-#include <unistd.h>
-#include <syscall.h>
-#include <linux/futex.h>
-#include <sys/time.h>
-#include <climits>
 #include <atomic>
+#include <climits>
 #include <thread>
+
 #include <glog/logging.h>
 
 #include <folly/Bits.h>
 #include <folly/Likely.h>
+#include <folly/detail/Futex.h>
+#include <folly/portability/SysTime.h>
+#include <folly/portability/Unistd.h>
 
 
 namespace folly {
 
-namespace detail {
-
-inline int futex(int* uaddr, int op, int val, const timespec* timeout,
-                 int* uaddr2, int val3) noexcept {
-  return syscall(SYS_futex, uaddr, op, val, timeout, uaddr2, val3);
-}
-
-}  // namespace detail
-
 /**
  * Event count: a condition variable for lock free algorithms.
  *
@@ -126,14 +116,10 @@ class EventCount {
   static_assert(sizeof(int) == 4, "bad platform");
   static_assert(sizeof(uint32_t) == 4, "bad platform");
   static_assert(sizeof(uint64_t) == 8, "bad platform");
+  static_assert(sizeof(std::atomic<uint64_t>) == 8, "bad platform");
+  static_assert(sizeof(detail::Futex<std::atomic>) == 4, "bad platform");
 
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-  static constexpr size_t kEpochOffset = 1;
-#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
-  static constexpr size_t kEpochOffset = 0;  // in units of sizeof(int)
-#else
-# error Your machine uses a weird endianness!
-#endif
+  static constexpr size_t kEpochOffset = kIsLittleEndian ? 1 : 0;
 
   // val_ stores the epoch in the most significant 32 bits and the
   // waiter count in the least significant 32 bits.
@@ -157,8 +143,8 @@ inline void EventCount::notifyAll() noexcept {
 inline void EventCount::doNotify(int n) noexcept {
   uint64_t prev = val_.fetch_add(kAddEpoch, std::memory_order_acq_rel);
   if (UNLIKELY(prev & kWaiterMask)) {
-    detail::futex(reinterpret_cast<int*>(&val_) + kEpochOffset,
-                  FUTEX_WAKE, n, nullptr, nullptr, 0);
+    (reinterpret_cast<detail::Futex<std::atomic>*>(&val_) + kEpochOffset)
+        ->futexWake(n);
   }
 }
 
@@ -177,8 +163,8 @@ inline void EventCount::cancelWait() noexcept {
 
 inline void EventCount::wait(Key key) noexcept {
   while ((val_.load(std::memory_order_acquire) >> kEpochShift) == key.epoch_) {
-    detail::futex(reinterpret_cast<int*>(&val_) + kEpochOffset,
-                  FUTEX_WAIT, key.epoch_, nullptr, nullptr, 0);
+    (reinterpret_cast<detail::Futex<std::atomic>*>(&val_) + kEpochOffset)
+        ->futexWait(key.epoch_);
   }
   // memory_order_relaxed would suffice for correctness, but the faster
   // #waiters gets to 0, the less likely it is that we'll do spurious wakeups
@@ -209,6 +195,4 @@ void EventCount::await(Condition condition) {
   }
 }
 
-}  // namespace folly
-
-#endif /* FOLLY_EXPERIMENTAL_EVENTCOUNT_H_ */
+} // namespace folly