Segmentation fault when trying to add binding
Hi, 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); +} + +value v2v_xml_xpath_eval_expression (value xpathctxv, value exprv) { CAMLparam2 (xpathctxv, exprv); diff --git a/v2v/xml.ml b/v2v/xml.ml index 78cb022..2e4d222 100644 --- a/v2v/xml.ml +++ b/v2v/xml.ml @@ -31,6 +31,7 @@ type node = doc * node_ptr external parse_memory : string -> doc = "v2v_xml_parse_memory" external xpath_new_context : doc -> xpathctx = "v2v_xml_xpath_new_context" external xpath_eval_expression : xpathctx -> string -> xpathobj = "v2v_xml_xpath_eval_expression" +external xpath_register_ns : string -> string -> xpathctx -> int = "v2v_xml_xpath_register_ns" external xpathobj_nr_nodes : xpathobj -> int = "v2v_xml_xpathobj_nr_nodes" external xpathobj_get_node_ptr : xpathobj -> int -> node_ptr = "v2v_xml_xpathobj_get_node_ptr" diff --git a/v2v/xml.mli b/v2v/xml.mli index 38bb9cd..cab4395 100644 --- a/v2v/xml.mli +++ b/v2v/xml.mli @@ -29,6 +29,8 @@ val xpath_new_context : doc -> xpathctx (** xmlXPathNewContext *) val xpath_eval_expression : xpathctx -> string -> xpathobj (** xmlXPathEvalExpression *) +val xpath_register_ns : string -> string -> xpathctx -> int +(** xmlXPathRegisterNs *) val xpathobj_nr_nodes : xpathobj -> int (** Get the number of nodes in the node set of the xmlXPathObjectPtr. *) ===================================================================================
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
On Tue, Aug 26, 2014 at 09:10:11AM +0200, Pino Toscano wrote:
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)
This too. Notice that Val_foo() means convert foo to value, and Foo_val() means convert value to foo. In that file, only node_ptr/xmlNodePtr can be cast directly from value to the C type, and that's for a very special and peculiar reason. For everything else you have to convert between value and the C type (and vice versa) using the appropriate macro. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into KVM guests. http://libguestfs.org/virt-v2v
On Tue, Aug 26, 2014 at 09:34:42AM +0300, Shahar Havivi wrote:
Hi,
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);
An 'int' isn't a 'value', so this will not work and likely segfault. For the representation of 'value' see: http://rwmj.wordpress.com/2009/08/04/ocaml-internals/#content (and follow up articles). In any case, here you need to turn the return value into an exception, ie something like this untested code: value v2v_xml_xpath_register_ns (value prefix, value uri, value xpathctx) { CAMLparam3 (prefix, uri, xpathctx); int r; r = xmlXPathRegisterNs (...); if (r == -1) caml_invalid_argument ("some suitable error message here ..."); /* return unit */ CAMLreturn (Val_unit); }
+external xpath_register_ns : string -> string -> xpathctx -> int = "v2v_xml_xpath_register_ns"
Needs to return unit, not int. If the libxml2 function returns -1 then this will throw an exception (Invalid_arg).
+val xpath_register_ns : string -> string -> xpathctx -> int +(** xmlXPathRegisterNs *)
Same here. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/
participants (3)
-
Pino Toscano -
Richard W.M. Jones -
Shahar Havivi