connected_components bug with listS listS graph

From: Claus Spacil (claus_at_[hidden])
Date: 2000-10-14 14:15:33

Hi all!

I am new to this mailing list, so i am not sure whether someone 
already reported this. Couldn't find it searching the boost egroup, 
though.

I'm using VC 6.0 SP3.

I was trying to use connected_components on a graph with a listS 
container for vertices. 

There's an (internal) index vertex property map. 

And i used an external property map 
(random_access_iterator_property_map) of
default_color_type associated with the index map.

I run into an access vialotion in the [] operator of 
random_access_iterator_property_map.

Looking at the call stack i figured out that the following piece of 
code
in depth_first_search.hpp lines 73 & 74 (3rd and 4th line of the 2nd 
variant of depth_first_search()) leads to the problem:

typedef typename 
graph_traits<VertexListGraph>::vertex_descriptor Vertex;

typename property_traits<ColorMap>::value_type c = get(color, 
Vertex());

using the functor Vertex() results in a call to get() for a key value of 
0.
since my color map uses vertex descriptors of std::list and not 
std::vector as key values it's easy to see why this must fail.

To work around the problem, i just let variable c uninitialized, since 
it's value seems to be of no meaning to the code anyway. That 
solved the problem for me.

Greetings
Claus