Mercurial > gnulib
view lib/signbitd.c @ 12559:c2cbabec01dd
update nearly all FSF copyright year lists to include 2010
Use the same procedure as for 2009, outlined in
http://thread.gmane.org/gmane.comp.lib.gnulib.bugs/20081
author | Jim Meyering <meyering@redhat.com> |
---|---|
date | Fri, 01 Jan 2010 10:31:12 +0100 |
parents | 0b09102d516e |
children | 97fc9a21a8fb |
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/* signbit() macro: Determine the sign bit of a floating-point number. Copyright (C) 2007-2010 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 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, see <http://www.gnu.org/licenses/>. */ #include <config.h> /* Specification. */ #include <math.h> #include <string.h> #include "isnand-nolibm.h" #include "float+.h" #ifdef gl_signbitd_OPTIMIZED_MACRO # undef gl_signbitd #endif int gl_signbitd (double arg) { #if defined DBL_SIGNBIT_WORD && defined DBL_SIGNBIT_BIT /* The use of a union to extract the bits of the representation of a 'long double' is safe in practice, despite of the "aliasing rules" of C99, because the GCC docs say "Even with '-fstrict-aliasing', type-punning is allowed, provided the memory is accessed through the union type." and similarly for other compilers. */ # define NWORDS \ ((sizeof (double) + sizeof (unsigned int) - 1) / sizeof (unsigned int)) union { double value; unsigned int word[NWORDS]; } m; m.value = arg; return (m.word[DBL_SIGNBIT_WORD] >> DBL_SIGNBIT_BIT) & 1; #elif HAVE_COPYSIGN_IN_LIBC return copysign (1.0, arg) < 0; #else /* This does not do the right thing for NaN, but this is irrelevant for most use cases. */ if (isnand (arg)) return 0; if (arg < 0.0) return 1; else if (arg == 0.0) { /* Distinguish 0.0 and -0.0. */ static double plus_zero = 0.0; double arg_mem = arg; return (memcmp (&plus_zero, &arg_mem, SIZEOF_DBL) != 0); } else return 0; #endif }