Re: [Boost-bugs] [Boost C++ Libraries] #3407: boost::call_once not re-entrant (at least in win32)

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #3407: boost::call_once not re-entrant (at least in win32)
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2009-09-06 14:58:26

#3407: boost::call_once not re-entrant (at least in win32)
-----------------------------------------------+----------------------------
 Reporter:  Vincent Falco <thevinn@…>          |       Owner:  anthonyw
     Type:  Bugs                               |      Status:  new     
Milestone:  Boost 1.41.0                       |   Component:  threads 
  Version:  Boost 1.40.0                       |    Severity:  Problem 
 Keywords:  threads                            |  
-----------------------------------------------+----------------------------

Comment(by steven_watanabe):

 The flag must be set after the function is called.  The reason is that if
 another thread calls call_once, it should block until the function is
 completed.  I'll also point out that there is no good behavior for a
 recursive call to call_once.  If it calls the function again, then f will
 be called twice.  If it does not, then whatever initialization that
 call_once is doing may be incomplete.  In either case, you have to know
 whether a call can be recursive and carefully design for it.  If it
 happens accidentally, you're probably toast regardless of how it behaves.
 In the face of recursive calls it is impossible to maintain the post-
 condition that the function has run exactly once.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/3407#comment:1>
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