Re: [xml] Memory leak / cleanup missing after node creation.

[Jose Commins <axora myrealbox com>]

        Many thanks Igor!

	The text node I am replacing it with is meant to remove all children 
from the old node, and after reading your excellent explanations I see 
where I have made the mistake - basically I didn't realise the old node 
remained unlinked but not free, and that I was continuing processing 
the old node thus causing the problems I was having.  I replaced the 
code below with:

...
                        newNode = xmlNewText(theTagReplacements[1]);
                        xmlReplaceNode(cur_node, newNode);
                        xmlFreeNode(cur_node);
                        cur_node = newNode;
...


	I understand now that a replaced/unlinked node still 'hangs around' 
and has to be freed.

	The code now works without leaks - you have solved my problem.  A 
thousand thanks!


Regards,
                Jose.


On 24 May 2004, at 4:19 pm, Igor Zlatkovic wrote:

> On 24/05/04 16:33, Jose Commins wrote:
> >     Thanks.  It is most unfortunate that I have to keep a list of the 
> > nodes, since if I free the node using xmlFreeNode before replacing it 
> > I lose the node I want to replace - if I free it afterwards I lose 
> > the node I replaced it with!
>
> You cannot free a node before you replace it or unlink it from the 
> document somehow. It would be like removing a link from a chain and 
> expecting the chain to be whole afterwards.
>
> The node you replaced it with should be in the document tree, where 
> the old node was.
>
> >     I guess I'll have to keep a list of newNode's that I have 
> > assigned, so I can free them later after I have finished with the 
> > doc.
>
> I think you have a different problem. In your code, you are replacing 
> an element node with a text node. Element nodes can have children, 
> text nodes cannot, so the new text node does not adopt the children of 
> the old element node. Few lines down the road, you process the 
> children of the old element node, means process a fragment which is 
> now outside your document tree. The old element node does not have 
> cur_node->next anymore, that link now belongs to the new text node.
>
>
> > static void process_XML_elements(xmlNode *a_node)
> > {
> > xmlNode *newNode = NULL;
> > xmlNode *cur_node = NULL;
> > for (cur_node = a_node; cur_node; cur_node = cur_node->next) {
> >   switch(cur_node->type)
> >   {
> >     case XML_ELEMENT_NODE:
> >       if(!strcmp("aTest", cur_node->name))
> >       {
> >          newNode = xmlNewText(theTagReplacements[1]);
> >          xmlReplaceNode(cur_node, newNode);
> >       }
> >       break;
> >     default:
> >       break;
> >   }
> >   process_XML_elements(cur_node->children);
> > }
> > }
>
>
> Ciao,
> Igor