Re: [boost] [UUID] version v12

Subject: Re: [boost] [UUID] version v12
From: Andy Tompkins (atompkins_at_[hidden])
Date: 2008-10-16 22:11:24

Hi Johannes,

On Mon, 13 Oct 2008 13:12:02 +0200, "Johannes Brunen"
<JBrunen_at_[hidden]> said:
> Hello Andy,
> 
> after some investigations, I think that I have found the origin of the 
> problem:
> 
> In seed_rng.hpp the following code is used:
> 
> template <typename UniformRandomNumberGenerator>
> inline void seed(UniformRandomNumberGenerator& rng)
> {
>     seed_rng seed_gen;
>     boost::generator_iterator<seed_rng> begin(&seed_gen);
>     boost::generator_iterator<seed_rng> end;
>     rng.seed(begin, end);
> }
> 
> Problematic is the construction of the end iterator. Looking into the
> code 
> (boost/generator_iterator.hpp) shows, that the default constructor of 
> generator_iterator does not initialize its member variables.
> 
> generator_iterator() {}
> 
> Howerver, the mersenne_twister seed code does compare the two given 
> iterators as shown below (boost/random/).
> 
> template<class It>
> void seed(It& first, It last)
> {
> int j;
> for(j = 0; j < n && first != last; ++j, ++first)
>   x[j] = *first;
> i = n;
> if(first == last && j < n)
>   throw std::invalid_argument("mersenne_twister::seed");
> }
> 
> As the end iterator is not initialized the way is open for all throwing
> the 
> invalid_argument exception.
> 
> Locally, I did solve the problem by patching the default constructor of 
> class generator_iterator.
> 
> If this is a valid solution of the problem, it would be fine if anyone 
> applies the correction to the boost code.
> 
> Greetings,
> Johannes
> 

I have put a new version in the boost vault.
http://www.boostpro.com/vault/index.php?action=downloadfile&filename=uuid_v13.zip&directory=&
It addresses this problem by making a copy of boost::generator_iterator
with your fix.

Regards,
  Andy.