Re: [Boost-users] Unexpected warning relating to boost::function, and size_t / unsigned

From: Igor R (boost.lists_at_[hidden])
Date: 2008-07-14 02:52:40

I'd like to join this question.
I've got the same strange behavior when using boost::hash, like this:

std::size_t hash_value(const Command &cmd)
{
  return boost::hash<std::size_t>()(cmd.id()); // id() returns std::sze_t
}

And I guess, the problem is not in a possible redefinition of size_t -
since everywhere in code the std::size_t is fully qualified...

2008/7/14, Matthew Bourdua <unknownmat_at_[hidden]>:
> Hello,
>
> I'm receiving a compiler warning (MSVC8.0) that does not make sense to me,
> and I wonder if this might be a boost related issue:
>
> #include <vector>
> #include <functional>
> #include <boost/function.hpp>
>
> int main()
> {
>   std::vector< std::size_t > sizes;
>   std::vector< unsigned > data;
>     boost::function< bool (unsigned, unsigned) > fn = std::greater< unsigned
> >();     fn( data.front(), 10 ); // NOTE: data is empty - will cause runtime
> error
> }
>
> The warning I get is:
> warning C4267: 'argument' : conversion from 'size_t' to 'unsigned int',
> possible loss of data
> referring to the last line in main().
>
> This warning goes away if I do either of the following:
> - Comment out the std::vector< std::size_t > sizes - this one baffles me.
> - Use a 'naked' std::greater< unsigned >() instead of a boost::function<
> bool (unsigned, unsigned) >() object.
>
> I wonder if size_t is somehow redefined in boost in a way that might be
> causing me some trouble?
>
> Any help would be appreciated, thanks.
>
> Matt
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>