[xml] Any outstanding bugs in closing parser contexts or running with different memory handlers?

[Sean Chittenden <sean chittenden org>]

I'm neck deep in memory problems and am not sure where to begin
looking.  I'm actually worried I've tickled a bug in Ruby because I'm
using its malloc/free routines, but I'd like to be sure.  Since I've
swapped out the memory routines, what's left of the libxml memory
accounting, or do I have to build my own and duplicate the *Loc()
routines only have them using ruby_xmalloc, free, etc?  I've pasted
the valgrind results in case anyone's interested or wants to take a
peak:

http://www.rubynet.org/valgrind-libxml.txt
http://www.rubynet.org/valgrind-libxml.txt.bz2

ctxtClose is a blatant rip off from someplace inside of the libxml
sources:

static void ctxtClose(FILE *f) {
  if (f != stdin) {
    fclose(f);
  }
}


... so I'm not really sure why I'm getting the following cryptic
error:

==19278== Invalid read of size 1
==19278==    at 0x40308758: (within /lib/libc-2.2.5.so)
==19278==    by 0x431B10BC: ctxtClose (ruby_xml_parser.c:17)
==19278==    by 0x432BCDAA: xmlFreeParserInputBuffer (xmlIO.c:1575)
==19278==    by 0x432A01CC: xmlFreeInputStream (parserInternals.c:1923)
==19278==    by 0x432A0B29: xmlFreeParserCtxt (parserInternals.c:2313)
==19278==    by 0x431B2A83: ruby_xml_parser_context_free (ruby_xml_parser_context.c:92)

==19278== Invalid read of size 2
==19278==    at 0x40308789: (within /lib/libc-2.2.5.so)
==19278==    by 0x431B10BC: ctxtClose (ruby_xml_parser.c:17)
==19278==    by 0x432BCDAA: xmlFreeParserInputBuffer (xmlIO.c:1575)
==19278==    by 0x432A01CC: xmlFreeInputStream (parserInternals.c:1923)
==19278==    by 0x432A0B29: xmlFreeParserCtxt (parserInternals.c:2313)
==19278==    by 0x431B2A83: ruby_xml_parser_context_free (ruby_xml_parser_context.c:92)

==19278== Invalid read of size 4
==19278==    at 0x403087CB: (within /lib/libc-2.2.5.so)
==19278==    by 0x431B10BC: ctxtClose (ruby_xml_parser.c:17)
==19278==    by 0x432BCDAA: xmlFreeParserInputBuffer (xmlIO.c:1575)
==19278==    by 0x432A01CC: xmlFreeInputStream (parserInternals.c:1923)
==19278==    by 0x432A0B29: xmlFreeParserCtxt (parserInternals.c:2313)
==19278==    by 0x431B2A83: ruby_xml_parser_context_free (ruby_xml_parser_context.c:92)

What's interesting is that the read size grows from 1 to 4.  Why I'm
not sure, and think that there could be a stray bit being written to
in Ruby, but I'm not 100% sure.  Since valgrind only runs on Linux,
I'd perfectly happy to chalk this up as a linux-ism, but it crashes on
FreeBSD too.  :-/  Anyone have any thoughts?  -sc

-- 
Sean Chittenden