Re: [libxml++] program crashes when parsing XML with accent

[Murray Cumming <murrayc murrayc com>]

On Tue, 2004-05-04 at 18:40 +0200, Christophe de VIENNE wrote:
> Hi,
> 
> 
> I could reproduce the problem with the saxparser example and the xml sample file from the bugzilla ticket.
> I obtain this bt:
> 
> #0  0x403b91b1 in kill () from /lib/libc.so.6
> #1  0x4014a9c1 in pthread_kill () from /lib/libpthread.so.0
> #2  0x4014accb in raise () from /lib/libpthread.so.0
> #3  0x403b8df4 in raise () from /lib/libc.so.6
> #4  0x403ba5a8 in abort () from /lib/libc.so.6
> #5  0x402bca74 in __cxa_call_unexpected () from /usr/lib/./libstdc++.so.5
> #6  0x402bcab1 in std::terminate () from /usr/lib/./libstdc++.so.5
> #7  0x402bcc21 in __cxa_throw () from /usr/lib/./libstdc++.so.5
> #8  0x40276a5c in std::__throw_length_error () from /usr/lib/./libstdc++.so.5
> #9  0x402af83f in std::string::_Rep::_S_create () from /usr/lib/./libstdc++.so.5
> #10 0x402b03a4 in std::string::_M_replace_safe<char const*> () from /usr/lib/./libstdc++.so.5
> #11 0x402ad23a in std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string () from /usr/lib/./libstdc++.so.5
> #12 0x401d28b4 in Glib::ustring::ustring () from /usr/lib/./libglibmm-2.3.so.2
> #13 0x40024924 in xmlpp::SaxParserCallback::characters (context=0x0, ch=0xbffff0a0 "égal", len=5) at saxparser.cc:390
> #14 0x4005dd0d in xmlParseCharDataComplex () from /usr/lib/./libxml2.so.2
> #15 0x4005d7d2 in xmlParseCharData () from /usr/lib/./libxml2.so.2
> #16 0x40066bf1 in xmlParseContent () from /usr/lib/./libxml2.so.2
> #17 0x40066fa9 in xmlParseElement () from /usr/lib/./libxml2.so.2
> #18 0x400682e3 in xmlParseDocument () from /usr/lib/./libxml2.so.2
> #19 0x4002383d in xmlpp::SaxParser::parse (this=0xbffff560) at saxparser.cc:152
> #20 0x4002398a in xmlpp::SaxParser::parse_file (this=0xbffff560, filename= 0xbffff590) at saxparser.cc:173
> #21 0x08049adc in main (argc=2, argv=0x0) at main.cc:45
> 
> We see at line #13 that the callback gives the string utf-8 encoded and it's length in characters. This is with no doubt correct, and those values are given to ustring constructor directly.
> 
> Going throught ustring sources I see that the constructor we use do this:
>     269 ustring::ustring(const char* src, ustring::size_type n)
>     270 :
>     271   string_ (src, utf8_byte_offset(src, n))
>     272 {}
> 
> knowing that std::__throw_length_error () is supposed to be raised if size is greater than max_size, I presume utf8_byte_offset returned std::string::npos.
> 
> My probably stupid question is the following:
> Murray, in ustring::ustring(const char* src, ustring::size_type n), is "n" supposed to be the length in utf-8 characters, or in bytes ?

I think it's meant to be the number of characters. That's not what I'd
expect, but I guess it makes sense in terms of translating std::string
to Glib::ustring.

Actually, in my debugger, the ch paramater to
SaxParserCallback::characters() seems to be 0, which is a more likely
cause for the crash. I guess we should check for 0.