X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Ffloor.c;h=cf29b196c331d2f8399287b706daf94a7724bfbc;hb=974b76b72e84d226e4bdfd9ec6f7d955e3d2a199;hp=0b2bb8a28807f1f1e8baabf929b0024f0a8cf83f;hpb=ab044c631f6655cfacc8ea4b1383f0cb7740326f;p=gnulib.git

diff --git a/lib/floor.c b/lib/floor.c
index 0b2bb8a28..cf29b196c 100644
--- a/lib/floor.c
+++ b/lib/floor.c
@@ -1,23 +1,24 @@
 /* Round towards negative infinity.
-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2010-2013 Free Software Foundation, Inc.
 
-   This program is free software; you can redistribute it and/or modify
+   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
-   the Free Software Foundation; either version 2, or (at your option)
-   any later version.
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
 
-   You should have received a copy of the GNU General Public License along
-   with this program; if not, write to the Free Software Foundation,
-   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 /* Written by Bruno Haible <bruno@clisp.org>, 2007.  */
 
-#include <config.h>
+#if ! defined USE_LONG_DOUBLE
+# include <config.h>
+#endif
 
 /* Specification.  */
 #include <math.h>
@@ -41,8 +42,14 @@
 # define L_(literal) literal##f
 #endif
 
+/* MSVC with option -fp:strict refuses to compile constant initializers that
+   contain floating-point operations.  Pacify this compiler.  */
+#ifdef _MSC_VER
+# pragma fenv_access (off)
+#endif
+
 /* 2^(MANT_DIG-1).  */
-static const double TWO_MANT_DIG =
+static const DOUBLE TWO_MANT_DIG =
   /* Assume MANT_DIG <= 5 * 31.
      Use the identity
        n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5).  */
@@ -64,20 +71,35 @@ FUNC (DOUBLE x)
   volatile DOUBLE y = x;
   volatile DOUBLE z = y;
 
-  /* Round to the next integer (nearest or up or down, doesn't matter).  */
   if (z > L_(0.0))
     {
-      z += TWO_MANT_DIG;
-      z -= TWO_MANT_DIG;
+      /* 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.  */
+      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))
     {
-      z -= TWO_MANT_DIG;
-      z += TWO_MANT_DIG;
+      /* 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);
+        }
     }
-  /* Enforce rounding down.  */
-  if (z > y)
-    z -= L_(1.0);
-
   return z;
 }