[Boost-bugs] [Boost C++ Libraries] #11514: Thread-unsafe (or non-optimal in C++11) static initialization in boost/spirit/home/qi/numeric/detail/numeric_utils.hpp

Subject: [Boost-bugs] [Boost C++ Libraries] #11514: Thread-unsafe (or non-optimal in C++11) static initialization in boost/spirit/home/qi/numeric/detail/numeric_utils.hpp
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-07-27 16:56:12

#11514: Thread-unsafe (or non-optimal in C++11) static initialization in
boost/spirit/home/qi/numeric/detail/numeric_utils.hpp
------------------------------------------------+---------------------
 Reporter:  Artem Tokmakov <artyom.tokmakov@…>  |      Owner:  djowel
     Type:  Bugs                                |     Status:  new
Milestone:  To Be Determined                    |  Component:  spirit
  Version:  Boost 1.58.0                        |   Severity:  Problem
 Keywords:  unsafe initialization               |
------------------------------------------------+---------------------
 This file (it's the same in boost 1.58 which I have too):
 boost/spirit/home/qi/numeric/detail/numeric_utils.hpp has following code
 (similar in a couple of places):


 {{{
 // Ensure n *= Radix will not overflow
 static T const max = (std::numeric_limits<T>::max)();
 static T const val = max / Radix;
 }}}

 Since static initialization is not thread-safe in Visual Studio (the one
 I'm using now is 2013 update 4), and because these variables are dependent
 on each other, this causes problems. Indeed, sometimes I get '''val'''
 initialized to 0, and other times to correct value.

 But even when "magic statics" are implemented, this will probably be not
 the most efficient implementation since a better one would be using, say,
 constexpr.

 There are couple of ways to fix this, and one with minimal changes
 (considering my minimal knowledge of boost constexpr machinery) would be:

 {{{
 // ## Note how two variables are initialized independently.
 static T const max = (std::numeric_limits<T>::max)();
 static T const val = (std::numeric_limits<T>::max)() / Radix;
 }}}

 Thanks!

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11514>
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