[Boost-bugs] [Boost C++ Libraries] #8730: Race condition in once_block.hpp

Subject: [Boost-bugs] [Boost C++ Libraries] #8730: Race condition in once_block.hpp
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-06-25 15:44:50

#8730: Race condition in once_block.hpp
------------------------------------------+---------------------
 Reporter:  apolukhin                     |      Owner:  andysem
     Type:  Bugs                          |     Status:  new
Milestone:  To Be Determined              |  Component:  log
  Version:  Boost 1.54.0                  |   Severity:  Problem
 Keywords:  call_once atomics thread log  |
------------------------------------------+---------------------
 First of all, `once_block_flag` is not thread safe. `status` variable
 shall be an atomic variable there.

 Another issue is `static boost::log::once_block_flag flag_var`. When
 previous issue will be fixed and  `once_block_flag` will become thread
 safe, keyword `static` will do bad things in C++03. Static variable
 `foo_type foo` inside method in C++03 is equal to:

 {{{
 // In global namespace
 bool is_foo_inited = false;
 char place_for_foo[sizeof(foo_type)];

 // in place where a static variable is used
 if (!is_foo_inited) {
     new (place_for_foo) foo_type(some parameters);
     is_foo_inited = true;
 }
 return reinterpret_cast<foo_type&>(*place_for_foo);
 }}}

 Beacuse `is_foo_inited` is not atomic and does not act as a spin-lock
 during initialization - race conditions are possible.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8730>
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