libstdc++: Encapsulate __gthread_cond_t as std::__condvar

This introduces a new internal utility, std::__condvar, which is a
simplified form of std::condition_variable. It has no dependency on
<chrono> or std::unique_lock, which allows it to be used in
<bits/atomic_wait.h>.

This avoids repeating the #ifdef __GTHREAD_COND_INIT preprocessor
conditions and associated logic for initializing a __gthread_cond_t
correctly. It also encapsulates most of the __gthread_cond_xxx functions
as member functions of __condvar.

libstdc++-v3/ChangeLog:

	* include/bits/atomic_timed_wait.h (__cond_wait_until_impl):
	Do not define when _GLIBCXX_HAVE_LINUX_FUTEX is defined. Use
	__condvar and mutex instead of __gthread_cond_t and
	unique_lock<mutex>.
	(__cond_wait_until): Likewise. Fix test for return value of
	__cond_wait_until_impl.
	(__timed_waiters::_M_do_wait_until): Use __condvar instead
	of __gthread_cond_t.
	* include/bits/atomic_wait.h: Remove <bits/unique_lock.h>
	include. Only include <bits/std_mutex.h> if not using futexes.
	(__platform_wait_max_value): Remove unused variable.
	(__waiters::lock_t): Use lock_guard instead of unique_lock.
	(__waiters::_M_cv): Use __condvar instead of __gthread_cond_t.
	(__waiters::_M_do_wait(__platform_wait_t)): Likewise.
	(__waiters::_M_notify()): Likewise. Use notify_one() if not
	asked to notify all.
	* include/bits/std_mutex.h (__condvar): New type.
	* include/std/condition_variable (condition_variable::_M_cond)
	(condition_variable::wait_until): Use __condvar instead of
	__gthread_cond_t.
	* src/c++11/condition_variable.cc (condition_variable): Define
	default constructor and destructor as defaulted.
	(condition_variable::wait, condition_variable::notify_one)
	(condition_variable::notify_all): Forward to corresponding
	member function of __condvar.

1 files changed, 4 insertions, 29 deletions

diff --git a/libstdc++-v3/src/c++11/condition_variable.cc b/libstdc++-v3/src/c++11/condition_variable.cc
index 19b03da..92721bb 100644
--- a/libstdc++-v3/src/c++11/condition_variable.cc
+++ b/libstdc++-v3/src/c++11/condition_variable.cc
@@ -31,51 +31,26 @@ namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
-#ifdef __GTHREAD_COND_INIT
   condition_variable::condition_variable() noexcept = default;
-#else
-  condition_variable::condition_variable() noexcept
-  {
-    __GTHREAD_COND_INIT_FUNCTION(&_M_cond);
-  }
-#endif
 
-  condition_variable::~condition_variable() noexcept
-  {
-    // XXX no thread blocked
-    /* int __e = */ __gthread_cond_destroy(&_M_cond);
-    // if __e == EBUSY then blocked
-  }
+  condition_variable::~condition_variable() noexcept = default;
 
   void
   condition_variable::wait(unique_lock<mutex>& __lock) noexcept
   {
-    int __e = __gthread_cond_wait(&_M_cond, __lock.mutex()->native_handle());
-
-    if (__e)
-      std::terminate();
+    _M_cond.wait(*__lock.mutex());
   }
 
   void
   condition_variable::notify_one() noexcept
   {
-    int __e = __gthread_cond_signal(&_M_cond);
-
-    // XXX not in spec
-    // EINVAL
-    if (__e)
-      __throw_system_error(__e);
+    _M_cond.notify_one();
   }
 
   void
   condition_variable::notify_all() noexcept
   {
-    int __e = __gthread_cond_broadcast(&_M_cond);
-
-    // XXX not in spec
-    // EINVAL
-    if (__e)
-      __throw_system_error(__e);
+    _M_cond.notify_all();
   }
 
   extern void