X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Ftrunc.c;h=73a33456111a072d601dc649c66dec7255166593;hb=f16415c07025fdec551dfc1dc7275c2a88819d44;hp=e8d3d87dc307005bac85bc3f6b18686abd813d1a;hpb=3db9b0d802e34ec28fc924076ae4c196bd7d23a9;p=gnulib.git

diff --git a/lib/trunc.c b/lib/trunc.c
index e8d3d87dc..73a334561 100644
--- a/lib/trunc.c
+++ b/lib/trunc.c
@@ -1,5 +1,5 @@
 /* Round towards zero.
-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2010-2011 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -16,30 +16,44 @@
 
 /* Written by Bruno Haible <bruno@clisp.org>, 2007.  */
 
-#include <config.h>
+#if ! defined USE_LONG_DOUBLE
+# include <config.h>
+#endif
 
 /* Specification.  */
 #include <math.h>
 
 #include <float.h>
 
+#undef MIN
+
 #ifdef USE_LONG_DOUBLE
 # define FUNC truncl
 # define DOUBLE long double
 # define MANT_DIG LDBL_MANT_DIG
+# define MIN LDBL_MIN
 # define L_(literal) literal##L
 #elif ! defined USE_FLOAT
 # define FUNC trunc
 # define DOUBLE double
 # define MANT_DIG DBL_MANT_DIG
+# define MIN DBL_MIN
 # define L_(literal) literal
 #else /* defined USE_FLOAT */
 # define FUNC truncf
 # define DOUBLE float
 # define MANT_DIG FLT_MANT_DIG
+# define MIN FLT_MIN
 # define L_(literal) literal##f
 #endif
 
+/* -0.0.  See minus-zero.h.  */
+#if defined __hpux || defined __sgi || defined __ICC
+# define MINUS_ZERO (-MIN * MIN)
+#else
+# define MINUS_ZERO L_(-0.0)
+#endif
+
 /* 2^(MANT_DIG-1).  */
 static const DOUBLE TWO_MANT_DIG =
   /* Assume MANT_DIG <= 5 * 31.
@@ -65,29 +79,37 @@ FUNC (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)
-	{
-	  /* Round to the next integer (nearest or up or down, doesn't matter).  */
-	  z += TWO_MANT_DIG;
-	  z -= TWO_MANT_DIG;
-	  /* Enforce rounding down.  */
-	  if (z > y)
-	    z -= L_(1.0);
-	}
+      else if (z < TWO_MANT_DIG)
+        {
+          /* Round to the next integer (nearest or up or down, doesn't matter).  */
+          z += TWO_MANT_DIG;
+          z -= TWO_MANT_DIG;
+          /* Enforce rounding down.  */
+          if (z > y)
+            z -= L_(1.0);
+        }
     }
   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)
-	{
-	  /* Round to the next integer (nearest or up or down, doesn't matter).  */
-	  z -= TWO_MANT_DIG;
-	  z += TWO_MANT_DIG;
-	  /* Enforce rounding up.  */
-	  if (z < y)
-	    z += L_(1.0);
-	}
+      else if (z > - TWO_MANT_DIG)
+        {
+          /* Round to the next integer (nearest or up or down, doesn't matter).  */
+          z -= TWO_MANT_DIG;
+          z += TWO_MANT_DIG;
+          /* Enforce rounding up.  */
+          if (z < y)
+            z += L_(1.0);
+        }
     }
   return z;
 }