Re: [xml] redicting parts of trees

[Rob Richards <rrichards ctindustries net>]

Kasimier Buchcik wrote:

> The context has just an initial "void * _private" field, to be able to
> extend it. Adding fields to it, at the end, won't break ABI
> compatibility.
>  
How do you not break compatibility? For example, A new field is added, 
which if not NULL would cause the execution of some function while 
inside the adopt node function. If someone where to create a context 
structure, without using some initialization function, then a crash most 
likely would occur as the field is not initialized to NULL.

Like the ctxt->aquireNsDecl(ctxt, cur->ns, &ns) function. When that 
actually gets added, how do I make sure it doesnt execute?
Will there be a flags field (some int)  that indicates the functions off 
the context to execute or will it end up testing:

if (ctxt->flags & DOM_CTXT_AQUIRE_NS) {
   ctxt->aquireNsDecl(ctxt, cur->ns, &ns)
}

or

if (ctxt->aquireNsDecl) {
   ctxt->aquireNsDecl(ctxt, cur->ns, &ns)
}

To avoid breaking stuff, shouldn't an additional function be added which 
returns an initialized context with all fields set to null and be the 
required way to grab the context or run the risk of crashing in future 
releases? This way when a context is needed, they would call the init 
function and then populate their context? As it would be bad if someone 
used the context structure directly not realizing new fields have been 
added and need to be initialized.

Rob