X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=tests%2Ftest-trunc2.c;h=748c045c78472d129bebbbc61923e0dbe28a667a;hb=ba0163712435ee40583ee8eb0dc289220b31fa35;hp=397e1ade0d1488d1e057b29cd09fd56dc36e1f60;hpb=b2e2010c7c902235b5efb5bd3c6529f61b093aa4;p=gnulib.git

diff --git a/tests/test-trunc2.c b/tests/test-trunc2.c
index 397e1ade0..748c045c7 100644
--- a/tests/test-trunc2.c
+++ b/tests/test-trunc2.c
@@ -16,6 +16,9 @@
 
 /* Written by Bruno Haible <bruno@clisp.org>, 2007.  */
 
+/* When this test fails on some platform, build it together with the gnulib
+   module 'fprintf-posix' for optimal debugging output.  */
+
 #include <config.h>
 
 #include <math.h>
@@ -26,6 +29,7 @@
 #include <stdio.h>
 
 #include "isnand-nolibm.h"
+#include "minus-zero.h"
 #include "macros.h"
 
 
@@ -35,6 +39,9 @@
 #define MANT_DIG DBL_MANT_DIG
 #define L_(literal) literal
 
+/* -0.0.  See minus-zero.h.  */
+#define MINUS_ZERO minus_zerod
+
 /* 2^(MANT_DIG-1).  */
 static const DOUBLE TWO_MANT_DIG =
   /* Assume MANT_DIG <= 5 * 31.
@@ -60,8 +67,12 @@ trunc_reference (DOUBLE x)
 
   if (z > L_(0.0))
     {
+      /* For 0 < x < 1, return +0.0 even if the current rounding mode is
+         FE_DOWNWARD.  */
+      if (z < L_(1.0))
+        z = L_(0.0);
       /* Avoid rounding errors for values near 2^k, where k >= MANT_DIG-1.  */
-      if (z < TWO_MANT_DIG)
+      else if (z < TWO_MANT_DIG)
         {
           /* Round to the next integer (nearest or up or down, doesn't matter).  */
           z += TWO_MANT_DIG;
@@ -73,8 +84,12 @@ trunc_reference (DOUBLE x)
     }
   else if (z < L_(0.0))
     {
+      /* For -1 < x < 0, return -0.0 regardless of the current rounding
+         mode.  */
+      if (z > L_(-1.0))
+        z = MINUS_ZERO;
       /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1.  */
-      if (z > - TWO_MANT_DIG)
+      else if (z > - TWO_MANT_DIG)
         {
           /* Round to the next integer (nearest or up or down, doesn't matter).  */
           z -= TWO_MANT_DIG;
@@ -123,8 +138,10 @@ check (double x)
       return 0;
     else
       {
+#if GNULIB_TEST_FPRINTF_POSIX
         fprintf (stderr, "trunc %g(%a) = %g(%a) or %g(%a)?\n",
                  x, x, reference, reference, result, result);
+#endif
         return 1;
       }
   }