Re: [xml] libxml2 API crazy?

[Nikita Churaev <lamefun x0r gmail com>]

Is this allowed by the C standard? And where is this documented?

On Mon, 2013-04-29 at 08:14 +0400, Nikolay Sivov wrote:
> On 4/29/2013 07:59, Nikita Churaev wrote:
> > No it's not.
> >
> > http://xmlsoft.org/html/libxml-tree.html#xmlDoc
> >
> > http://xmlsoft.org/html/libxml-tree.html#xmlNode
> >
> > xmlDoc has int compression instead of xmlNode's xmlNs
> I see what you mean. All node types are using same layout containing basic
> stuff to link node in a tree - up to 'doc' field. That's what a comment 
> in tree.h means:
>
> ---
> struct _xmlNode {
>      void           *_private;    /* application data */
>      xmlElementType   type;    /* type number, must be second ! */
>      const xmlChar   *name;      /* the name of the node, or the entity */
>      struct _xmlNode *children;    /* parent->childs link */
>      struct _xmlNode *last;    /* last child link */
>      struct _xmlNode *parent;    /* child->parent link */
>      struct _xmlNode *next;    /* next sibling link  */
>      struct _xmlNode *prev;    /* previous sibling link  */
>      struct _xmlDoc  *doc;    /* the containing document */
>
>      /* End of common part */
> ---
>
> So to be clean with casting it should have some sort of header struct 
> containing these fields only,
> and have every node type start with this header, it's just not done this 
> way. To be safe you always
> need to check type and cast appropriately.
> > On Mon, 2013-04-29 at 07:48 +0400, Nikolay Sivov wrote:
> > > On 4/29/2013 07:30, Nikita Churaev wrote:
> > > > #include <libxml/parser.h>
> > > > #include <libxml/tree.h>
> > > > #include <stdio.h>
> > > >
> > > > int
> > > > main (int argc, char** argv)
> > > > {
> > > >     xmlDocPtr doc = xmlReadMemory("<doc/>", 6, "egg.xml", NULL, 0);
> > > >
> > > >                     /* XmlNode */            /* XmlDoc */
> > > >     printf("%s\n", (doc->children->parent == doc) ? "true" : "false");
> > > >     return 0;
> > > > }
> > > >
> > > > This gives out "true"... Why? xmlNode.parent is xmlNodePtr... So I can't
> > > > just rely on xmlNode pointers to actually point to xmlNode?
> > > Just take a look what xmlDocPtr actually is - document is also a node.
> > > >    I looked all
> > > > around the API reference and tutorials and found nothing on this topic.
> > > >
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