[Boost-commit] svn:boost r61180 - in branches/release: boost/uuid libs/uuid

Subject: [Boost-commit] svn:boost r61180 - in branches/release: boost/uuid libs/uuid
From: atompkins_at_[hidden]
Date: 2010-04-10 11:13:41

Author: atompkins
Date: 2010-04-10 11:13:40 EDT (Sat, 10 Apr 2010)
New Revision: 61180
URL: http://svn.boost.org/trac/boost/changeset/61180

Log:
Added notes to documentation about using Valgrind
Added some comments to seed_rng.hpp
Text files modified: 
   branches/release/boost/uuid/seed_rng.hpp |     4 ++++                                    
   branches/release/libs/uuid/uuid.html     |    13 +++++++++++++                           
   2 files changed, 17 insertions(+), 0 deletions(-)

Modified: branches/release/boost/uuid/seed_rng.hpp
==============================================================================
--- branches/release/boost/uuid/seed_rng.hpp	(original)
+++ branches/release/boost/uuid/seed_rng.hpp	2010-04-10 11:13:40 EDT (Sat, 10 Apr 2010)
@@ -75,6 +75,7 @@
     //BOOST_STATIC_CONSTANT(unsigned int, max_value = UINT_MAX);
 
 public:
+    // note: rd_ intentionally left uninitialized
     seed_rng()
         : rd_index_(5)
         , random_(std::fopen( "/dev/urandom", "rb" ))
@@ -111,6 +112,7 @@
 private:
     static unsigned int * sha1_random_digest_state_()
     {
+        // intentionally left uninitialized
         static unsigned int state[ 5 ];
         return state;
     }
@@ -143,6 +145,7 @@
         }
 
         {
+            // intentionally left uninitialized
             unsigned char buffer[ 20 ];
 
             if(random_)
@@ -156,6 +159,7 @@
         }
 
         {
+            // *p is intentionally left uninitialized
             unsigned int * p = new unsigned int;
 
             sha.process_bytes( (unsigned char const*)p, sizeof( *p ) );

Modified: branches/release/libs/uuid/uuid.html
==============================================================================
--- branches/release/libs/uuid/uuid.html	(original)
+++ branches/release/libs/uuid/uuid.html	2010-04-10 11:13:40 EDT (Sat, 10 Apr 2010)
@@ -587,6 +587,19 @@
 values including <tt>std::time(0)</tt>, <tt>std::clock()</tt>, uninitialized
 data, value return from <tt>new unsigned int</tt>, etc..
 
+<p>Using Valgrind produces a number of false
+positives with the default constructor of <tt>boost::uuids::basic_random_generator</tt>.  
+One solution is to suppress the errors as described in
+Valgrind's documentation.
+Another solution is to use a different constructor of <tt>boost::uuids::basic_random_generator</tt>
+and explicitly pass in a random number generator.
+<pre>
+boost::mt19937 ran;
+ran.seed(time(NULL)); // one should likely seed in a better way
+boost::uuids::basic_random_generator&lt;boost::mt19937&gt; gen(&ran);
+boost::uuids::uuid u = gen();
+</pre>
+
 <p>The <tt>boost::uuids::name_generator</tt> class uses the SHA-1 hash function to
 compute the <b>uuid</b>.