[xml] SEGV...using the api correctly?

[Jon <jon forums gmail com>]

On Win7 32bit in an simple validation app using a statically linked libxml2, the following code SEGV's

  https://github.com/jonforums/xvalid/blob/master/src/xvalid.c#L58-119

at line 114 in `xmlFreeParserInputBuffer(input)` with the following gdb info:

C:\projects\xvalid-git>gdb --args xval.exe --xsd test\nested.xsd test\nested.xml
...
Breakpoint 1, xvalid__xsd_validate (ctx=0x22fe88) at src/xvalid.c:107
107             xsd_valid_ctx = NULL;
(gdb) s
108             xmlFreeParserInputBuffer(input);
(gdb)
xmlFreeParserInputBuffer (in=0x2f1f98) at xmlIO.c:2417
2417        if (in == NULL) return;
(gdb)
2419        if (in->raw) {
(gdb)
2420            xmlBufferFree(in->raw);
(gdb)
xmlBufferFree (buf=0xfeeefeee) at tree.c:6980
6980        if (buf == NULL) {
(gdb)
6988        if ((buf->alloc == XML_BUFFER_ALLOC_IO) &&
(gdb)

Program received signal SIGSEGV, Segmentation fault.
xmlBufferFree (buf=0xfeeefeee) at tree.c:6988
6988        if ((buf->alloc == XML_BUFFER_ALLOC_IO) &&


I statically link to a mingw gcc 4.6.2 built libxml2 v2.7.8 configured as:

  https://github.com/jonforums/xvalid/blob/master/doc/faq.mkd

I'm ramping up on the codebase and API so I don't yet grok the API. Deleting lines 114 and 115 make the SEGV 
go away, but I think removing those lines is wrong as I want to iterate over a bunch of xml files, validate 
each one, and then cleanup between iterations.

While the last part of the gdb trace surprises me, I'd like to better understand how the API *should* be used 
in this XSD validation scenario as I'm clearly not doing it right.

In general, when and how should `xmlFreeXXX` fcns be used, and what specifically am I doing wrong in my 
snippet?

Jon

---
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