math: add exception handling functionality

According to standards SVID and SYSV.
Modified lgamma calling in case when 'signgam' variable should not be used.

Signed-off-by: Waldemar Brodkorb <wbx@uclibc-ng.org>

1 files changed, 32 insertions, 13 deletions

diff --git a/libm/w_exp2.c b/libm/w_exp2.c
index e00277abf..1215c2e92 100644
--- a/libm/w_exp2.c
+++ b/libm/w_exp2.c
@@ -1,19 +1,38 @@
-/*
- * ====================================================
- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
- *
- * Developed at SunPro, a Sun Microsystems, Inc. business.
- * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice
- * is preserved.
- * ====================================================
- */
+/* Copyright (C) 2011-2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
 
-#include "math.h"
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
 #include "math_private.h"
 
-double exp2(double x)
+/* wrapper exp2(x) */
+double
+exp2 (double x)
 {
-	return pow(2.0, x);
+#if __UCLIBC_HAS_FENV__
+  double z = pow(2.0, x);
+  if (__builtin_expect (!isfinite (z) || z == 0, 0)
+      && isfinite (x) && _LIB_VERSION != _IEEE_)
+    /* exp2 overflow: 44, exp2 underflow: 45 */
+    return __kernel_standard (x, x, 44 + !!signbit (x));
+
+  return z;
+#else
+  return pow(2.0, x);
+#endif
 }
 libm_hidden_def(exp2)