[igraph] Problem with C attribute handler

[Juanjo Jimenez]

We're working on a SNA project and we've been using igraph library with R. Basically, all the programming is done in C.

We added an importer for a graph format defined by us. It's for directed graphs with vertex and arc attributes. Apparently, up to this point we had no trouble and all works fine. We can access to the vertex and arc attributes from the prompt in the R interpreter.

Right now, we're dealing with a C function that needs to query the attributes of the vertices and arcs and we are having some problems.

After building and installing, we import a graph with our importer and then when our function is called we get this message from the interpreter:

At cattributes.c:753 : Unknown attribute, Invalid value

In our C function we're using igraph_cattribute_VANV to get all the values of all the values of a vertex attribute. Here's where the error comes up. Debbuging our code, we ended in this function defined in cattributes.c:

igraph_bool_t igraph_i_cattribute_find(const igraph_vector_ptr_t *ptrvec, const char *name, long int *idx) { 
long int i, n=igraph_vector_ptr_size(ptrvec); 
igraph_bool_t l=0; 

…
 
}

The variable n is a negative number after calling  igraph_vector_ptr_size when should be 2. 

From the igraph documentation, we know this:

“… There is an experimental attribute handler that can be used from C code. ...”

and were wondering if our problem is related to this experimental state or is something else.

Thanks and sorry about my English.