Le 13/01/13 19:41, Andrey Semashev a écrit :
On Sun, Jan 13, 2013 at 10:32 PM, Vicente J. Botet Escriba <vicente.botet@wanadoo.fr> wrote:
Well, the definition removes the copy constructor and the assignment
struct once_flag { BOOST_THREAD_NO_COPYABLE(once_flag)
After adding
static boost::once_flag once2 = BOOST_ONCE_INIT;
to example/once.cpp
and I'm seen the following kind of error on a lot of C++11 compilers Does this mean that BOOST_ONCE_INIT is not supported and tested with C++11 compilers? Seems an oversight to me.
Maybe it is worth to add a portable extension to the C++11 to ensure compatibility. This would be very useful, IMHO, since the same code could be used for both C++03 and C++11.
BTW, couldn't the lock scope be reduced as follows
BOOST_THREAD_DECL void commit_once_region(once_flag& flag) BOOST_NOEXCEPT { atomic_type& f = reinterpret_cast< atomic_type& >(flag.storage); { // ++++++++ pthread::pthread_mutex_scoped_lock lk(&once_mutex); f.store(initialized, memory_order_release); } // ++++++++ BOOST_VERIFY(!pthread_cond_broadcast(&once_cv));
} No, this is not correct because this would lead to missed notifications. Condition variables should always be used under the locked mutex.
I believed it also but the mutex shouldn't be locked while doing notifications, only when you change the condition and when you wait for the condition to be notified. Best, Vicente