[xml] Understanding memory usage and cross-references

[Patrick O'Brien <pobrien9 comcast net>]

Hello list -

in the source file keys.c, in the function xsltFreeKeyDef(xsltKeyDefPtr 
keyd), near the end of the function there are the lines:

   if (keyd->nsList != NULL)
       xmlFree(keyd->nsList);

I am wondering why the code isn't

   if (keyd->nsList != NULL)
       xmlFreeNsList(keyd->nsList);

A runtime type inspection mechanism could allow for type recognition on 
free(), but I believe this is not the case here.

*****

In addition, the structure _xsltKeyDef { } has a data member named 
xmlNodePtr inst, and this is not freed in xsltFreeKeyDef(); I assume it 
is so because inst is a reference to a structure allocated elsewhere 
that will be freed elsewhere. 

This is by way of remarking that there is no obvious way to know what 
sub-structures are allocated from a given structure, and what structures 
are just working references, short of reading all related code.

The motivation for these observations is a review of the code en route 
to a better understanding of the cost involved in writing a serializer 
for the xsltStylesheet structure.

Regards,

pob