On Mon, May 06, 2013 at 12:41:22PM +0000, Kuhnke, Christoph (I/EF-56, extern)
wrote:
> Dear creators of libxml2,
Hallo,
might be better to subscribe to the list so i don't have to dig your
messages in the mailing-list bounces, which I tend to forget doing !
> I think I found a slight mistake in function
> xpath.c:xmlXPathStringEvalNumber()
> of libxml2 version 2.9.0.
>
> For data type "float" in xml files resp. xml schemas
> [1] states "The mantissa must be a decimal number."
> [2] contains details:
> An optional leading sign is allowed.
> If the sign is omitted, "+" is assumed.
> and names "+100000.00" as valid example for a decimal.
>
> In contrast when first non-whitespace-character of it's argument is a '+',
> xpath.c:xmlXPathStringEvalNumber() stops parsing and return 0.0.
>
> To make libxml2 conform to [1] I suggest the following change:
>
> Replace 3 lines 10098 through 10100 (incl.)
> by the following 7 lines
>
> if ((*cur != '.') && ((*cur < '0') || (*cur > '9')) && (*cur != '-') &&
> (*cur != '+')) {
> return(xmlXPathNAN);
> }
> if (*cur == '+') {
> isneg = 0;
> cur++;
> }
>
>
> Please let me know, what you think about my proposal.
>
> References
> [1] http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/datatypes.html#float
> 3.2.4.1 Lexical representation
> [2] http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/datatypes.html#decimal
> 3.2.3.1 Lexical representation
Ah well I am sorry but that's the wrong reference ;-)
Surprizingly enough xpath.c:xmlXPathStringEvalNumber() is part of the
implementation of XPath (version 1),
http://www.w3.org/TR/xpath/#section-Number-Functions
"a string that consists of optional whitespace followed by an optional
minus sign followed by a Number followed by whitespace is converted to
the IEEE 754 number that is nearest (according to the IEEE 754
round-to-nearest rule) to the mathematical value represented by the
string; any other string is converted to NaN"
[30] Number ::= Digits ('.' Digits?)?
| '.' Digits
[31] Digits ::= [0-9]+
basically no "+" is allowed by XPath 1 for the beginning of numbers
so the function is I think correct.
Libxml2 actually has a xml Schemas (version 1) datatype implementation
and it does check float values, the code is in
xmlSchemaValAtomicType() in xmlschemastypes.c
see around line 2393, it does accept a leading "+"
It's a feature, not a bug, at least at the libxml2 level, at the
W3C spec level it is a slight incoherence...
Daniel
--
Daniel Veillard | Open Source and Standards, Red Hat
[email protected] | libxml Gnome XML XSLT toolkit http://xmlsoft.org/
http://veillard.com/ | virtualization library http://libvirt.org/
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