From: Mike Crowe <mac@mcrowe.com>
Date: Wed, 1 Aug 2018 15:39:57 +0000 (+0000)
Subject: Use steady_clock to implement condition_variable::wait_for
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=9e68aa3cc52956ea99bb726c3c29ce0581b9f7e7;p=gcc.git

Use steady_clock to implement condition_variable::wait_for

The C++ standard says that std::condition_variable::wait_for should be
implemented to be equivalent to:

  return wait_until(lock, chrono::steady_clock::now() + rel_time);

But the existing implementation uses chrono::system_clock. Now that
wait_until has potentially-different behaviour for chrono::steady_clock,
let's at least try to wait using the correct clock.

2018-08-01  Mike Crowe  <mac@mcrowe.com>

	* include/std/condition_variable (wait_for): Use steady_clock.

From-SVN: r263225
---

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index dc4cc141530..71c01f94997 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,7 @@
+2018-08-01  Mike Crowe  <mac@mcrowe.com>
+
+	* include/std/condition_variable (wait_for): Use steady_clock.
+
 2018-08-01  Mike Crowe  <mac@mcrowe.com>
 
 	* include/std/condition_variable (wait_until): Only report timeout
diff --git a/libstdc++-v3/include/std/condition_variable b/libstdc++-v3/include/std/condition_variable
index c00afa2b7ae..1f84ea324eb 100644
--- a/libstdc++-v3/include/std/condition_variable
+++ b/libstdc++-v3/include/std/condition_variable
@@ -66,6 +66,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   class condition_variable
   {
     typedef chrono::system_clock	__clock_t;
+    typedef chrono::steady_clock	__steady_clock_t;
     typedef __gthread_cond_t		__native_type;
 
 #ifdef __GTHREAD_COND_INIT
@@ -144,11 +145,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       wait_for(unique_lock<mutex>& __lock,
 	       const chrono::duration<_Rep, _Period>& __rtime)
       {
-	using __dur = typename __clock_t::duration;
+	using __dur = typename __steady_clock_t::duration;
 	auto __reltime = chrono::duration_cast<__dur>(__rtime);
 	if (__reltime < __rtime)
 	  ++__reltime;
-	return wait_until(__lock, __clock_t::now() + __reltime);
+	return wait_until(__lock, __steady_clock_t::now() + __reltime);
       }
 
     template<typename _Rep, typename _Period, typename _Predicate>