Re: [xml] XPath Infinities

[Bjorn Reese <breese mail1 stofanet dk>]

Daniel Veillard wrote:

>   this whole issue is a huge mess ...

Indeed. We ought to extract all the NaN and Inf stuff into a separate file.

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

Actually, I am not sure that the patch in that bugreport solves the problem.
There seems to be two problems involved

 1. getting the compiler to accept the division by zero (it usually ouputs
    a warning, but that's ok)
 2. getting the program to produce a NaN (normally it just returns 0 instead)

I did some experimentations, and it turned out that two different solutions
were needed on Alpha, depending on your compiler.

 o with GCC the workaround is to ignore SIGFPE.
 o with DECC (the vendor CC) the -ieee compiler option must be used.

I verified this will a small test program, not with libxml.

I have attached two small patches for libxml. Unfortunately, I have not
tested them myself as I don't have access to the GNOME CVS from the Alpha
machine. Could somebody check them out, and report whether they work or not?
If possible, I would like to hear if they work with both GCC and the vendor
CC.

> > 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

There has got to be a better way.

Index: xpath.c
===================================================================
RCS file: /cvs/gnome/gnome-xml/xpath.c,v
retrieving revision 1.107
diff -c -r1.107 xpath.c
*** xpath.c     2001/04/28 14:35:02     1.107
--- xpath.c     2001/04/28 15:04:14
***************
*** 39,44 ****
--- 39,48 ----
  #ifdef HAVE_CTYPE_H
  #include <ctype.h>
  #endif
+ #if defined(__osf__) && defined(__GNUC__)
+ #include <signal.h>
+ #define FPE_WORKAROUND
+ #endif
  
  #include <libxml/xmlmemory.h>
  #include <libxml/tree.h>
***************
*** 156,161 ****
--- 160,169 ----
      static int initialized = 0;
  
      if (initialized) return;
+ 
+ #ifdef FPE_WORKAROUND
+     signal(SIGFPE, SIG_IGN);
+ #endif
  
  #ifdef XPATH_USE_DIVISION_SHORTCUTS
      xmlXPathNAN = 0;

Index: configure.in
===================================================================
RCS file: /cvs/gnome/gnome-xml/configure.in,v
retrieving revision 1.97
diff -c -r1.97 configure.in
*** configure.in        2001/04/23 13:41:34     1.97
--- configure.in        2001/04/28 15:02:36
***************
*** 157,170 ****
  XML_CFLAGS=""
  
  dnl
! dnl Workaround for HP native compiler
! dnl http://bugs.gnome.org/db/31/3163.html
  dnl
  if test "${GCC}" != "yes" ; then
      case "${host}" in
            *-*-hpux* )
               CFLAGS="${CFLAGS} -Wp,-H30000"
               ;;
      esac
  else
      CFLAGS="${CFLAGS} -Wall"
--- 157,174 ----
  XML_CFLAGS=""
  
  dnl
! dnl Workaround for native compilers
! dnl  HP  : http://bugs.gnome.org/db/31/3163.html
! dnl  DEC : Enable NaN/Inf
  dnl
  if test "${GCC}" != "yes" ; then
      case "${host}" in
            *-*-hpux* )
               CFLAGS="${CFLAGS} -Wp,-H30000"
               ;;
+           *-dec-osf* )
+                CFLAGS="${CFLAGS} -ieee"
+                ;;
      esac
  else
      CFLAGS="${CFLAGS} -Wall"