Re: How to get rid of VC warning C4239?

On Jul 6, 3:32 pm, Ron Natalie <r...@spamcop.net> wrote:


Thank you for the reply. I think the first choice won't work for me,
since it breaks my xml API (i will explain it later). The second
choice... sorry but i did not understand what you wanted to tell me...
I think the current impl's copy semantics is already to copy the PIMPL
(what they do is to copy the boost::shared_ptr object, which is the
PIMPL).

For the first choice... One of the goal of the basic_xml_node class
template is to make the interface pointer-free. For example, i have a
MsxmlNode class that uses msxml, and a LibxmlNode that uses libxml.
Both classes implement a member function called parent, like this:

class LibxmlNode {
public:
    LibxmlNode* parent();
    ...
};

class MsxmlNode {
public:
    MsxmlNode* parent();
    ...
};

Thus in my basic_xml_node class template, i implement the parent()
function to hide pointers (the memory management is implemented by the
library, and client don't need to worry about that).

template<class XmlNode>
class basic_xml_node {

    typedef basic_xml_node<XmlNode> node_type;

private:
    explicit basic_xml_node(XmlNode* pimpl): pimpl_(pimpl) { }

public:
    node_type parent() {
        XmlNode* px = pimpl_->parent();
        return node_type(px);
    }
    ...

private:
    XmlNode* pimpl_;
};

Thus, getting the parent node from one node is trivial:

typedef basic_xml_node<LibxmlNode> xml_node; // or, use MsxmlNode
xml_node child = ...;
xml_node parent = child.parent();
....

I want to keep the API trivial to use, and to disallow client code to
operate directly on pointers. But unfortunately, such implementation
requires that my basic_xml_node is "copyable" (in auto_ptr style).

Any help will be appreciated!

Regards.
ZHENG Zhong

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