[Boost-bugs] [Boost C++ Libraries] #4002: UUID documentation improvement

Subject: [Boost-bugs] [Boost C++ Libraries] #4002: UUID documentation improvement
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-03-13 03:24:11

#4002: UUID documentation improvement
---------------------------------+------------------------------------------
 Reporter:  harris.pc@…          |       Owner:  atompkins   
     Type:  Bugs                 |      Status:  new         
Milestone:  Boost 1.43.0         |   Component:  uuid        
  Version:  Boost 1.42.0         |    Severity:  Optimization
 Keywords:                       |  
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 I get "uninitialised value(s)" warnings in valgrind when I use the
 following code:

 boost::uuids::random_generator gen;
 boost::uuids::uuid u = gen();
 if (u == u) // for valgrind's benefit
   whatever();

 In the example, when I do not supply a random number generator to 'gen',
 it calls:
         detail::seed(*pURNG);

 Which does not initialise all its state variables (like rd_[]) before
 generating random numbers.

 I assume this is done to try and generate decent random numbers from
 uninitialised memory, especially when there is no /dev/urandom or similar
 available.  That is ok, I suppose.

 However, it makes valgrind very noisy when comparing uuids and thus
 generates a lot of false-positives to sift through.

 It would be great if the documentation could talk a bit about this, and
 also suggest that you use a pattern like the following if the library-user
 wants to silence valgrind reports:

 boost::mt19937 ran;
 uuids::random_generator gen(ran);

 It would be nice if it could also tell the library user why this might not
 be such a good idea. (eg mt19937 doesn't seed the random values as
 randomly as uuid's seed_rnd.hpp, right?).

 Or perhaps you can surround the detail::seed() call with #ifdefs to allow
 the user to control when uninitialised memory is used for seeding (helpful
 to turn off when debugging).

 Thanks,
 Paul

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/4002>
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