Re: [Boost-users] Boost Graph: vertex class has no copy constructor

Subject: Re: [Boost-users] Boost Graph: vertex class has no copy constructor
From: Andrew Sutton (andrew.n.sutton_at_[hidden])
Date: 2010-03-26 17:18:31

> The "easy" workaround is to simply have the graph refer to BasicBlock by
>> pointer instead of actually owning it. Pointers are definitely default and
>> copy constructible :)
>>
>
> Yes, I had tried that, and the pointers are added to the graph okay using
> add_vertex, but when I try to pull them out using, say, graph[0], my program
> segfaults. I have no idea what I'm doing wrong.

It's not surprising that graph[0] crashes for directed_graph; it's vertex
descriptors are actually list iterators. It turns out that 0 is an implicit
constructor for directed_graph<...>::null_vertex().

The (current BGL) documentation doesn't spell this out very well, and almost
none of the examples demonstrate this fact. I think you could use:

graph[vertex(g, 0)]

but that might be O(n).

 I should do maybe:
>
>  typedef adjacency_list<vecS, vecS, directedS, BasicBlock*> TimingGraph;
>

If you're not going to remove vertices, then that's probably a good bet. I
forget if this is good for removing edges also. I'm guessing "no".

Andrew Sutton
andrew.n.sutton_at_[hidden]