On 4/28/06, Matthias Troyer <troyer@itp.phys.ethz.ch> wrote:
Hi,
Trying to compile our ALPS project sources (http://alps.comp- phys.org) with the CVS HEAD I encountered a number of problems with the BGL concept checking. In particular on MacOS X, using the Apple g+ + 4.0.1, I encounter problems in depth_first_search.hpp with:
template <class Visitor, class Graph> class DFSVisitorConcept { public: void constraints() { function_requires< CopyConstructibleConcept<Visitor> >(); vis.initialize_vertex(u, g); vis.start_vertex(u, g); vis.discover_vertex(u, g); vis.examine_edge(e, g); vis.tree_edge(e, g); vis.back_edge(e, g); vis.forward_or_cross_edge(e, g); vis.finish_vertex(u, g); } private: Visitor vis; Graph g; typename graph_traits<Graph>::vertex_descriptor u; typename graph_traits<Graph>::edge_descriptor e; };
Somehow this tries to instantiate a default constructor for the visitor and the graph. Since some graph types do not have a default constructor and no default constructor should actually be required, I want to ask whether this is a bug in the compiler or in the concept checks?
Matthias
I don't believe models of the Graph or DFSVisitor concepts are required to be default constructable. I tried to take a look at this compiling ALPS-1.3a1, but couldn't reproduce the error with g++ 4.0.3 on Linux. As far as I can tell neither DFSVisitorConcept nor CopyConstructibleConcept use a default constructor. However, if for some reason your (custom) visitor class tries to default construct a graph in a member function (initialize_vertex(), start_vertex(), etc.) this could cause the error. Could you give a specific example of code that causes the error? Daniel Walker