From bug-request at octave dot org Thu Dec 16 17:59:26 2004
Subject: Re: signbit on linux/gcc 3.2+
From: Orion Poplawski <orion at cora dot nwra dot com>
To: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
CC: bug at octave dot org
Date: Thu, 16 Dec 2004 17:49:34 -0600

John W. Eaton wrote:
> That's fine, for systems using GCC and GNU libstdc++.  But we can't
> simply use
> 
>   #include <cmath>
>   using std::signbit;
> 
> on all systems, which is what I think your patch did.
> 
> jwe

Okay, here's another attempt.  I'm leaving in the HAVE_SIGNBIT check 
because I suspect that is still necessary for __MINGW32__ (since it 
looks like it has the function but perhaps not the declaration).  I've 
remove <math.h> on the assumption that we are all C++ code.  Other 
question would be whether to have the #error statement, or just get rid 
of the #else and not define lo_ieee_signbit and let other code complain.

Does the following work on the sun?

   #include <cmath>
   #include <iostream>
   int
   main (void)
   {
     std::cerr << signbit (-1.0) << std::endl;

     return 0;
   }

Just for fun, see 
http://osl.iu.edu/~tveldhui/papers/techniques/techniques01.html

--- octave-2.1.64/configure.in.orig     2004-11-11 22:40:15.000000000 -0700
+++ octave-2.1.64/configure.in  2004-12-16 16:34:16.209266151 -0700
 at @ -1153,6 +1153,7 @@
    ;;
    *)
      AC_CHECK_FUNCS(finite isnan isinf copysign signbit)
+    AC_CHECK_DECLS(signbit,,,[#include <math.h>])
    ;;
  esac

--- octave-2.1.64/liboctave/lo-ieee.h.orig      2003-09-05 
10:55:42.000000000 -0600
+++ octave-2.1.64/liboctave/lo-ieee.h   2004-12-16 16:34:01.509814447 -0700
 at @ -24,6 +24,13 @@
  #define octave_liboctave_ieee_h 1

+/* Use c++ signbit */
+#include <cmath>
+/* GNUC puts it in std:: */
+#ifdef __GNUC__
+using std::signbit;
+#endif
+
  #ifdef __cplusplus
  extern "C" {
  #endif

 at @ -72,7 +79,7 @@

  #if defined (signbit)
  #define lo_ieee_signbit(x) signbit (x)
-#elif defined (HAVE_SIGNBIT)
+#elif defined (HAVE_DECL_SIGNBIT) || defined (HAVE_SIGNBIT)
  #if defined (__MINGW32__)
  extern int signbit (double);
  #endif
 at @ -82,7 +89,7 @@
  #elif defined (HAVE_COPYSIGN)
  #define lo_ieee_signbit(x) (x < 0 || copysign (1.0, x) < 0)
  #else
-#define lo_ieee_signbit(x) 0
+#error "No signbit definition?!"
  #endif

  #ifdef __cplusplus

-- 
Orion Poplawski
System Administrator                   303-415-9701 x222
Colorado Research Associates/NWRA      FAX: 303-415-9702
3380 Mitchell Lane, Boulder CO 80301   http://www.co-ra.com



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