Re: [xml] XPath Infinities

[Daniel Veillard <veillard redhat com>]

On Fri, Apr 27, 2001 at 05:25:58PM +0200, Igor Zlatkovic wrote:
> Hello Daniel, everybody
>
> I encountered a slight difficulty while building version 2.3.7 under
> Win32/MSCC. The compiler refuses to divide a constant by zero. The recent
> changes in xpath.c which introduce these divisions broke the build under
> Win32/MSCC.

  this whole issue is a huge mess ...

> Namely, if you let MSCC divide a variable by zero, you get a NaN or
> positive/negative infinity, depends on what the variable contains, as was
> the intention. For some reason, MSCC considers it an error to divide a
> constant by zero and assign the result to a variable.

  yet another buggy compiler :-\

> someone with Linux on alpha recently said that his setup wants this to be
> just the other way around? 

  http://bugzilla.gnome.org/show_bug.cgi?id=52979

> I would suggest the following patch to xpath.c. It makes no difference to
> those who succeed compiling 2.3.7 as it is. Those of us who use MSCC and
> similar compilers would then be responsible to define this
> XPATH_USE_DIVISION_SHORTCUTS macro somewhere. The alternative to this seems
> to be disabling XPath under Win32/MSCC.
>
> What do you think? 

   Considering that compiler A and compiler B refuse to behave decently
on the same code we will have to use #ifdefs :-(
   Removing XPath is annoying since libxslt requires it

> + #ifdef XPATH_USE_DIVISION_SHORTCUTS
> +     xmlXPathNAN /= 0.0;
> +     xmlXPathPINF /= 0.0;
> +     xmlXPathNINF /= 0.0;
> + #else
>       xmlXPathNAN = 0.0 / 0.0;
>
>       xmlXPathPINF = 1 / 0.0;
>
>       xmlXPathNINF = -1 / 0.0;
> + #endif

  or rather:

#ifdef XPATH_USE_DIVISION_SHORTCUTS
        xmlXPathNAN = 0;
        xmlXPathNAN /= 0.0;
        xmlXPathPINF = 1;
        xmlXPathPINF /= 0.0;
        xmlXPathNINF = -1;
        xmlXPathNINF /= 0.0;
#else
        xmlXPathNAN = 0.0 / 0.0;
        xmlXPathPINF = 1 / 0.0;
        xmlXPathNINF = -1 / 0.0;
#endif

  I let you provide the patch to the Windows include to define
the XPATH_USE_DIVISION_SHORTCUTS macro.

Daniel

-- 
Daniel Veillard      | Red Hat Network http://redhat.com/products/network/
veillard redhat com  | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
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