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      1 /* $NetBSD: qnan.c,v 1.2 2006/01/25 15:27:42 kleink Exp $ */
      2 
      3 /****************************************************************
      4 
      5 The author of this software is David M. Gay.
      6 
      7 Copyright (C) 2005 by David M. Gay
      8 All Rights Reserved
      9 
     10 Permission to use, copy, modify, and distribute this software and its
     11 documentation for any purpose and without fee is hereby granted,
     12 provided that the above copyright notice appear in all copies and that
     13 both that the copyright notice and this permission notice and warranty
     14 disclaimer appear in supporting documentation, and that the name of
     15 the author or any of his current or former employers not be used in
     16 advertising or publicity pertaining to distribution of the software
     17 without specific, written prior permission.
     18 
     19 THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
     20 INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.  IN
     21 NO EVENT SHALL THE AUTHOR OR ANY OF HIS CURRENT OR FORMER EMPLOYERS BE
     22 LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
     23 DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
     24 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
     25 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
     26 SOFTWARE.
     27 
     28 ****************************************************************/
     29 
     30 /* Please send bug reports to David M. Gay (dmg at acm dot org,
     31  * with " at " changed at "@" and " dot " changed to ".").	*/
     32 
     33 /* Program to compute quiet NaNs of various precisions (float,	*/
     34 /* double, and perhaps long double) on the current system,	*/
     35 /* provided the system uses binary IEEE (P754) arithmetic.	*/
     36 /* Note that one system's quiet NaN may be a signaling NaN on	*/
     37 /* another system.  The IEEE arithmetic standards (P754, P854)	*/
     38 /* do not specify how to distinguish signaling NaNs from quiet	*/
     39 /* ones, and this detail varies across systems.	 The computed	*/
     40 /* NaN values are encoded in #defines for values for an		*/
     41 /* unsigned 32-bit integer type, called Ulong below, and	*/
     42 /* (for long double) perhaps as unsigned short values.  Once	*/
     43 /* upon a time, there were PC compilers for Intel CPUs that	*/
     44 /* had sizeof(long double) = 10.  Are such compilers still	*/
     45 /* distributed?							*/
     46 
     47 #include <stdio.h>
     48 #include "arith.h"
     49 
     50 #ifndef Long
     51 #define Long long
     52 #endif
     53 
     54 typedef unsigned Long Ulong;
     55 
     56 #undef HAVE_IEEE
     57 #ifdef IEEE_LITTLE_ENDIAN
     58 #define _0 1
     59 #define _1 0
     60 #define HAVE_IEEE
     61 #endif
     62 #ifdef IEEE_BIG_ENDIAN
     63 #define _0 0
     64 #define _1 1
     65 #define HAVE_IEEE
     66 #endif
     67 
     68 #define UL (unsigned long)
     69 
     70  int
     71 main(void)
     72 {
     73 #ifdef HAVE_IEEE
     74 	typedef union {
     75 		float f;
     76 		double d;
     77 		Ulong L[4];
     78 #ifndef NO_LONG_LONG
     79 		unsigned short u[5];
     80 		long double D;
     81 #endif
     82 		} U;
     83 	U a, b, c;
     84 	int i;
     85 
     86 	a.L[0] = b.L[0] = 0x7f800000;
     87 	c.f = a.f - b.f;
     88 	printf("#define f_QNAN 0x%lx\n", UL c.L[0]);
     89 	a.L[_0] = b.L[_0] = 0x7ff00000;
     90 	a.L[_1] = b.L[_1] = 0;
     91 	c.d = a.d - b.d;	/* quiet NaN */
     92 	printf("#define d_QNAN0 0x%lx\n", UL c.L[0]);
     93 	printf("#define d_QNAN1 0x%lx\n", UL c.L[1]);
     94 #ifdef NO_LONG_LONG
     95 	for(i = 0; i < 4; i++)
     96 		printf("#define ld_QNAN%d 0xffffffff\n", i);
     97 	for(i = 0; i < 5; i++)
     98 		printf("#define ldus_QNAN%d 0xffff\n", i);
     99 #else
    100 	b.D = c.D = a.d;
    101 	if (printf("") < 0)
    102 		c.D = 37;	/* never executed; just defeat optimization */
    103 	a.L[2] = a.L[3] = 0;
    104 	a.D = b.D - c.D;
    105 	for(i = 0; i < 4; i++)
    106 		printf("#define ld_QNAN%d 0x%lx\n", i, UL a.L[i]);
    107 	for(i = 0; i < 5; i++)
    108 		printf("#define ldus_QNAN%d 0x%x\n", i, a.u[i]);
    109 #endif
    110 #endif /* HAVE_IEEE */
    111 	return 0;
    112 	}
    113