Re: [xslt] boolval of node sets

[Daniel Veillard <veillard redhat com>]

On Thu, Oct 28, 2010 at 02:22:52PM -0400, Phil Shafer wrote:
> Is this behavior just a bug or am I missing something?   The
> XPath spec says boolean() requires "a node-set is true if and only if it is non-empty",
> but the xmlXPathNewNodeSet() and xmlXPathNewValueTree()
> functions hardcode the value to 0 and 1, respectively:
> 
> xmlXPathObjectPtr
> xmlXPathNewNodeSet(xmlNodePtr val) {
>     xmlXPathObjectPtr ret;
> ...
>     ret->boolval = 0;
>     ret->nodesetval = xmlXPathNodeSetCreate(val);
> ...
> xmlXPathObjectPtr
> xmlXPathNewValueTree(xmlNodePtr val) {
>     xmlXPathObjectPtr ret;
> ...
>     ret->boolval = 1;
>     ret->user = (void *) val;
>     ret->nodesetval = xmlXPathNodeSetCreate(val);
> ...
> 
> It looks like xmlXPathNewValueTree() is always called
> with a non-NULL tree, but there are >20 places where
> xmlXPathNewNodeSet is called with NULL.
> 
> Is the value of the boolval field updated elsewhere
> or is this a problem?

  just that boolval is meant to carry an information which
is not what the boolean() value will return.

> Any objections to the fix:
> 
> -     ret->boolval = 0;
> +     ret->boolval = val ? 1 : 0;

  This is likely to break EXSLT, so no

> While I'm here: a minor bug in xmlXPathNodeSetAdd() can
> make invalid node sets if xmlRealloc fails:
> 
> void
> xmlXPathNodeSetAdd(xmlNodeSetPtr cur, xmlNodePtr val) {
> ...
>         cur->nodeMax *= 2;
>         temp = (xmlNodePtr *) xmlRealloc(cur->nodeTab, cur->nodeMax *
>                                       sizeof(xmlNodePtr));
>         if (temp == NULL) {
>             xmlXPathErrMemory(NULL, "growing nodeset\n");
>             return;
>         }
>         cur->nodeTab = temp;
> ...
> 
> nodeMax is changed even if the realloc fails, so the next
> attempt to add will end in bad news.  I'll submit this and
> a patch via bugzilla.

  Ah right it's a bug, a libxml2 bug, I'm fixing this in git,

   thanks,

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
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