[Bug 53531] FTDI Vinculum II IDE gets "Out of memory" error on startup

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=53531

--- Comment #2 from Damjan Jovanovic <damjan.jov at gmail.com> ---
The problematic XML document, is just this single node:

<IDEConfig xmlns=\"http:///ide/MySchema.xsd\"/>

libxml2 converts namespace definition attributes ("xmlns:XYZ") into "struct
xmlNs" and makes them available as a linked list on their parent struct
xmlNode, pointed to by struct xmlNode's "nsDef" field. These "struct xmlNs"
instances are not xmlNode subtypes, but just a simple struct with little more
than "prefix" and "href" fields, and the linked list pointers. All other
(non-namespace-definition) attributes go into struct xmlNode's "properties" and
are (closer to) full-blown xmlNode subtypes with their many fields.

MSXML on the other hand, treats namespace definition attributes as ordinary
attributes, and provides the full IXMLDOMAttribute interface for them.

Before the commit causing the "regression", Wine just provided the
non-namespace-definition attributes in IXMLDOMNode::get_attributes(). In the
IXMLDOMNamedNodeMap returned by that method, IXMLDOMNamedNodeMap::get_length()
returned 0 for the XML tag in question here.

The application was happy with this and proceeded further.

The commit then changed this behaviour, by starting to returning the union of
struct xmlNode's "properties" and "nsDef" lists from
IXMLDOMNode::get_attributes(). IXMLDOMNamedNodeMap::get_length() then became 1,
and IXMLDOMNamedNodeMap::get_item(0) failed as originally described.

Now converting
xmlns:XYZ="href"
attributes to IXMLDOMAttributes works well, but the default namespace attribute
xmlns="href"
fails and returns the error. Why?

Once the namespace for the given index to IXMLDOMNamedNodeMap::get_item() is
found (variable "ns"), the code in domelem_get_item() first creates a new
namespace with prefix "xmlns" and href "http://www.w3.org/2000/xmlns/", then
creates an attribute node using that new namespace, and the matched namespace's
prefix and href (so as to produce xmlns:prefix=href). When the matched
namespace is the default namespace, prefix is NULL, and xmlNewNsProp() does not
allow a NULL name argument (prefix parameter).

---snip---
    xmlns = xmlNewNs(NULL, BAD_CAST "http://www.w3.org/2000/xmlns/", BAD_CAST
"xmlns");
    if (!xmlns)
        return E_OUTOFMEMORY;

    curr = xmlNewNsProp(NULL, xmlns, ns->prefix, ns->href);
    if (!curr) {
        xmlFreeNs(xmlns);
        return E_OUTOFMEMORY;
    }
---snip---

One way to fix, is when ns->prefix is NULL, create "curr" using
xmlNewProp(NULL, "xmlns", ns->href) instead of xmlNewNsProp(). I am not sure
whether that will behave correctly in other calls though.

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