On Thu, Sep 23, 2010 at 9:25 AM, Igor R wrote:

...

m_ioService.post(m_strand.wrap( boost::bind(&LogWriter::append, (*logWritersItr), _logMessage, _logLevelString) ));

The second param of Bind, (*logWritersItr), is a shared_ptr of LogWriter's subclass. The signature of LogWriter::append() is as following:

virtual void append(const std::string& _logMessage, const std::string& _logLevelString) = 0;

Base on document at http://www.boost.org/doc/libs/1_44_0/libs/bind/bind.html, the way I use bind will duplicate a copy of that shared_ptr. Any idea when will the duplicated shared_ptr become invalid so that the reference count decreases by one?

bind() takes your shared_ptr by value, so it won't become "invalid". After io_service executes your functor, it will be destroyed, so all its internal copies of that shared_ptr will be destroyed as well. _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

I think I don't quite completely understand functor.., is it by C++ that a functor will be destroyed automatically once executed? Or is this a feature from boost.bind?

On Sep 23, 2010, at 9:59 AM, Shiou Ming Lee wrote:

On Thu, Sep 23, 2010 at 9:25 AM, Igor R wrote:

...

m_ioService.post(m_strand.wrap( boost::bind(&LogWriter::append, (*logWritersItr), _logMessage, _logLevelString) ));

The second param of Bind, (*logWritersItr), is a shared_ptr of LogWriter's subclass. The signature of LogWriter::append() is as following:

virtual void append(const std::string& _logMessage, const std::string& _logLevelString) = 0;

Base on document at http://www.boost.org/doc/libs/1_44_0/libs/bind/bind.html, the way I use bind will duplicate a copy of that shared_ptr. Any idea when will the duplicated shared_ptr become invalid so that the reference count decreases by one?

bind() takes your shared_ptr by value, so it won't become "invalid". After io_service executes your functor, it will be destroyed, so all its internal copies of that shared_ptr will be destroyed as well. _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

I think I don't quite completely understand functor.., is it by C++ that a functor will be destroyed automatically once executed? Or is this a feature from boost.bind?

I think that you're thinking too hard about this. It's not a feature from boost.bind, it's just standard C++ lifetime rules. 1) The shared_ptr is copied into the bind object. (use count for the shared_ptr ++) 2) The bind object is passed (by value) to m_ioService.post. (use count for the shared_ptr++) *) The original bind object gets destroyed (goes out of scope, whatever) (use count for the shared_ptr--) *) When m_ioService.post returns, the copy of the bind object that was passed to it is destroyed (use count for the shared_ptr--) the last two are '*'s rather than 3/4 since I don't remember the order (and it doesn't really matter, either). ;-) If m_ioService.post makes copies of the functor and/or the shared pointer internally, then the use count for the shared pointer will be incremented for each copy, and decremented when a copy is destroyed. -- Marshall