[Libguestfs] Segmentation fault when trying to add binding

[Pino Toscano]

Hi,

On Tuesday 26 August 2014 09:34:42 Shahar Havivi wrote:
> I am trying to add xmlXPathRegisterNs() to v2v/xml-c.c but I get a seg
> fault, the signature should be:
> http://xmlsoft.org/html/libxml-xpathInternals.html#xmlXPathRegisterNs
> 
> I think I am wrong in CAMLparam and CAMLlocal...,
> Following is the patch:
> 
> ======================================================================
> diff --git a/v2v/xml-c.c b/v2v/xml-c.c
> index 4c9bc77..a917c24 100644
> --- a/v2v/xml-c.c
> +++ b/v2v/xml-c.c
> @@ -141,6 +141,16 @@ v2v_xml_xpath_new_context (value docv)
>  }
> 
>  value
> +v2v_xml_xpath_register_ns (value prefix, value uri, value xpathctx)
> +{
> +  CAMLparam3 (prefix, uri, xpathctx);
> +  CAMLlocal1 (retval);
> +  retval = xmlXPathRegisterNs (BAD_CAST String_val (prefix), BAD_CAST String_val (uri), xpathctx);
> +
> +  CAMLreturn (retval);
> +}
> +

First of all, you are using the xpathctx parameter directly as
parameter for xmlXPathRegisterNs, while it is an OCaml value which
wraps the actual object; see how it is done in e.g.
v2v_xml_xpath_eval_expression, using the Xpathctx_val macro.

Second, the order of the arguments in your xmlXPathRegisterNs is wrong:
- yours: xmlXPathRegisterNs(prefix, uri, ctxt)
- actual function: xmlXPathRegisterNs(ctxt, prefix, uri)

-- 
Pino Toscano