Re: [Boost-users] [property_map] bit vector as property map

From: Douglas Gregor (doug.gregor_at_[hidden])
Date: 2007-02-09 10:15:08

On Feb 9, 2007, at 2:38 AM, Sebastian Weber wrote:
> At least that's how I understood, how the property_map concept works.
> However, if I use a bit-vector the above scheme breaks down to work:
>
> std::vector<bool> bit_props(num_vertices(my_graph), false)
>
> bfs_search(..., make_my_vistor(&bit_props[0]), ...)
>
> The compiler compiles these lines, but complains that a temprorary is
> passed as a reference to make_my_visitor and the code generated  
> crashes.
> My system is a Ubununtu Edgy with boost 1.33.1 and g++ 4.1.2. Any  
> ideas
> why this happens and what I can do here?

The problem here is that vector<bool> does a space "optimization" by  
packing bool values into individual bits, and you can't take the  
address of a bit. Instead of trying to get a pointer to the bits, use  
iterators into the bit vector, e.g.,

   bfs_search(..., make_my_vistor(bit_props.begin()), ...)

        Cheers,
        Doug