On Dec 17, 2012, at 2:44 AM, Markos Zaharioudakis <[email protected]> wrote:
> size:size(<a><b>foo</b></a>) returns 101. This is wrong because just
> sizeof(ElementNode) is 52 and the tree <a><b>foo</b></a> consists of 2
> element nodes, one text node and one (hidden) attribute node.
>
> The reason for this wrong result is in this struct:
>
> template<typename T>
> struct size_traits<T*,false> {
> static size_t alloc_sizeof( T *p ) {
> return p ? mem_sizeof( *p ) : 0;
> }
> };
>
> Basically, an InternalNode has a vector of XmlNode*. So, the above struct is
> instantiated with T being XmlNode. Then, mem_sizeof(XmlNode) is called
> returning just 20 (== sizeof(XmlNode)).
I've looked at this a bit more and I still don't understand why it's wrong.
Ignoring everything else, the alloc_size() specialization for pointers seems
correct.
For a vector<XmlNode*>, it should iterate through the vector's elements. For
each element, it should call the above alloc_sizeof() for XmlNode*. That in
turn should call mem_sizeof(XmlNode) which is sizeof(XmlNode) +
alloc_sizeof(XmlNode). alloc_sizeof(XmlNode) turns into
size_traits<XmlNode>::alloc_sizeof(t).
XmlNode is derived from store::Item that has a virtual alloc_size(). The
specialization of size_traits for classes that have an alloc_size() member
function is called. Therefore, I don't see where the mistake is.
- Paul
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