[Boost-bugs] [Boost C++ Libraries] #11647: add cleanup expired connections API

Subject: [Boost-bugs] [Boost C++ Libraries] #11647: add cleanup expired connections API
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-09-13 03:04:10

#11647: add cleanup expired connections API
-------------------------------------+----------------------
 Reporter:  Lutts Cao <lutts.cao@…>  |      Owner:  fmhess
     Type:  Feature Requests         |     Status:  new
Milestone:  To Be Determined         |  Component:  signals2
  Version:  Boost 1.59.0             |   Severity:  Problem
 Keywords:                           |
-------------------------------------+----------------------
 when use signals2 with tracked shared object, it will cause memory leak
 when the shared track object which is allocated with allocated_shared() or
 make_shared() is destructed

 another problem is: after the shared track object is destructed,
 signals2::connection::connected() will return false, and
 signals2::connection::disconnect() will do nothing

 according to signals2's code, expired connection cleanup will happen after
 operator() is called, and maybe happen when signal.connect() is called.
 '''there is a problem when the signal is rarely emited, which means the
 time between successive operator() calls is long''

 I have tried boost 1.59.0, expired connection cause memory leak is still a
 problem.

 I suggested to add an explicit cleanup API to signals2::signal class to
 let the user cleanup expired connections explicitly

 or '''if you think add such an API is not a must, may be you can add a
 comment in boost.signals2 document to warn the users that there may be
 memory leak.'''

 == make_shared() and allocated_shared() in boost ==

 document can be found at
 http://www.boost.org/doc/libs/1_59_0/libs/smart_ptr/make_shared.html


 it is explicitly said these two function templates will use a single
 allocation, '''eliminating a significant portion of shared_ptr's
 construction overhead. This eliminates one of the major efficiency
 complaints about shared_ptr'''

 == make_shared() and allocated_shared() in C++11 standard spec ===

 in C++11 standard section 20.7.2.2.6.6 at page 573: '''Implementations are
 encouraged, but not required, to perform no more than one memory
 allocation.'''

 == make_shared() and allocated_shared() in Compiler implementations ==

 as far as I know, GCC, CLang and Microsoft Visual Studio all use '''single
 allocation''

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11647>
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