[webkit-dev] gdom_x_path_evaluator_create_ns_resolver [was: webkit #16401]

[Luke Kenneth Casson Leighton]

[taking this discussion onto webkit-dev for the benefit of other
people who may wish to use the glib / gobject bindings in the future]

On 6/6/09, Leon Winter <lwi at ring0.de> wrote:
> Hi,
>
>  @Luke: how is XPath supposed to work?
>
>  GdomXPathResult *res;
>     GdomXPathEvaluator evaluator;
>     char *exp = "//html:a";
>     GdomDocument *doc = get_dom_document();
>     GdomNodeList *els = gdom_document_get_elements_by_tag_name(doc,
>  "body");
>     GdomNode *body = gdom_node_list_item(els, 0);
>     GdomXPathNSResolver *resolver =
>  gdom_x_path_evaluator_create_ns_resolver(&evaluator, body);
>
>  segfaults right at the last line. I found new creation methid for
>  GdomXPathEvaluator, perhaps there should be one.

ok - thanks to mark rowe for highlighting the deliberate mistake:
https://bugs.webkit.org/show_bug.cgi?id=16401#c202

the first argument to any of the glib / gobject bindings needs to be
the object of the type which matches the IDL class from which the
function was auto-generated, so:

this function in Document.idl:
        XPathNSResolver    createNSResolver(in Node nodeResolver);

results in a function in GdomDocument.h:
    WEBKIT_API GdomXPathNSResolver *
    gdom_document_create_ns_resolver (GdomDocument *thiz, GdomNode *
                                                                node_resolver);

so as you can see, you have passed in an (uninitialised!) pointer to
"GdomXPathEvaluator evaluator", not a pointer to the GdomDocument
object - hence the segfault.

try this instead:

GdomXPathNSResolver *resolver =
gdom_x_path_evaluator_create_ns_resolver(doc, body);

l.