2 dnl Copyright (C) 2007-2010 Free Software Foundation, Inc.
3 dnl This file is free software; the Free Software Foundation
4 dnl gives unlimited permission to copy and/or distribute it,
5 dnl with or without modifications, as long as this notice is preserved.
9 AC_REQUIRE([gl_MATH_H_DEFAULTS])
10 AC_CACHE_CHECK([for signbit macro], [gl_cv_func_signbit],
15 /* If signbit is defined as a function, don't use it, since calling it for
16 'float' or 'long double' arguments would involve conversions.
17 If signbit is not declared at all but exists as a library function, don't
18 use it, since the prototype may not match.
19 If signbit is not declared at all but exists as a compiler built-in, don't
20 use it, since it's preferable to use __builtin_signbit* (no warnings,
23 # error "signbit should be a macro"
26 ]gl_SIGNBIT_TEST_PROGRAM
28 [gl_cv_func_signbit=yes],
29 [gl_cv_func_signbit=no],
30 [gl_cv_func_signbit="guessing no"])
32 dnl GCC 4.0 and newer provides three built-ins for signbit.
33 dnl They can be used without warnings, also in C++, regardless of <math.h>.
34 dnl But they may expand to calls to functions, which may or may not be in
36 AC_CACHE_CHECK([for signbit compiler built-ins], [gl_cv_func_signbit_gcc],
42 (sizeof (x) == sizeof (long double) ? __builtin_signbitl (x) : \
43 sizeof (x) == sizeof (double) ? __builtin_signbit (x) : \
44 __builtin_signbitf (x))
46 # error "signbit should be three compiler built-ins"
49 ]gl_SIGNBIT_TEST_PROGRAM
51 [gl_cv_func_signbit_gcc=yes],
52 [gl_cv_func_signbit_gcc=no],
53 [gl_cv_func_signbit_gcc="guessing no"])
55 dnl Use the compiler built-ins whenever possible, because they are more
56 dnl efficient than the system library functions (if they exist).
57 if test "$gl_cv_func_signbit_gcc" = yes; then
58 REPLACE_SIGNBIT_USING_GCC=1
60 if test "$gl_cv_func_signbit" != yes; then
65 gl_FLOAT_SIGN_LOCATION
66 gl_DOUBLE_SIGN_LOCATION
67 gl_LONG_DOUBLE_SIGN_LOCATION
68 if test "$gl_cv_cc_float_signbit" = unknown; then
69 dnl Test whether copysignf() is declared.
70 AC_CHECK_DECLS([copysignf], , , [#include <math.h>])
71 if test "$ac_cv_have_decl_copysignf" = yes; then
72 dnl Test whether copysignf() can be used without libm.
73 AC_CACHE_CHECK([whether copysignf can be used without linking with libm],
74 [gl_cv_func_copysignf_no_libm],
80 [[return copysignf (x, y) < 0;]])],
81 [gl_cv_func_copysignf_no_libm=yes],
82 [gl_cv_func_copysignf_no_libm=no])
84 if test $gl_cv_func_copysignf_no_libm = yes; then
85 AC_DEFINE([HAVE_COPYSIGNF_IN_LIBC], [1],
86 [Define if the copysignf function is declared in <math.h> and available in libc.])
90 if test "$gl_cv_cc_double_signbit" = unknown; then
91 dnl Test whether copysign() is declared.
92 AC_CHECK_DECLS([copysign], , , [#include <math.h>])
93 if test "$ac_cv_have_decl_copysign" = yes; then
94 dnl Test whether copysign() can be used without libm.
95 AC_CACHE_CHECK([whether copysign can be used without linking with libm],
96 [gl_cv_func_copysign_no_libm],
102 [[return copysign (x, y) < 0;]])],
103 [gl_cv_func_copysign_no_libm=yes],
104 [gl_cv_func_copysign_no_libm=no])
106 if test $gl_cv_func_copysign_no_libm = yes; then
107 AC_DEFINE([HAVE_COPYSIGN_IN_LIBC], [1],
108 [Define if the copysign function is declared in <math.h> and available in libc.])
112 if test "$gl_cv_cc_long_double_signbit" = unknown; then
113 dnl Test whether copysignl() is declared.
114 AC_CHECK_DECLS([copysignl], , , [#include <math.h>])
115 if test "$ac_cv_have_decl_copysignl" = yes; then
116 dnl Test whether copysignl() can be used without libm.
117 AC_CACHE_CHECK([whether copysignl can be used without linking with libm],
118 [gl_cv_func_copysignl_no_libm],
124 [[return copysignl (x, y) < 0;]])],
125 [gl_cv_func_copysignl_no_libm=yes],
126 [gl_cv_func_copysignl_no_libm=no])
128 if test $gl_cv_func_copysignl_no_libm = yes; then
129 AC_DEFINE([HAVE_COPYSIGNL_IN_LIBC], [1],
130 [Define if the copysignl function is declared in <math.h> and available in libc.])
138 AC_DEFUN([gl_SIGNBIT_TEST_PROGRAM], [[
140 Needed because GCC 4 constant-folds __builtin_signbitl (literal)
141 but cannot constant-fold __builtin_signbitl (variable). */
147 /* HP cc on HP-UX 10.20 has a bug with the constant expression -0.0.
148 So we use -p0f and -p0d instead. */
153 /* On HP-UX 10.20, negating 0.0L does not yield -0.0L.
154 So we use another constant expression instead.
155 But that expression does not work on other platforms, such as when
156 cross-compiling to PowerPC on MacOS X 10.5. */
157 long double p0l = 0.0L;
158 #if defined __hpux || defined __sgi
159 long double m0l = -LDBL_MIN * LDBL_MIN;
161 long double m0l = -p0l;
166 float plus_inf = 1.0f / p0f;
167 float minus_inf = -1.0f / p0f;
168 if (!(!signbit (255.0f)
171 && (memcmp (&m0f, &p0f, sizeof (float)) == 0 || signbit (m0f))
172 && !signbit (plus_inf)
173 && signbit (minus_inf)))
179 double plus_inf = 1.0 / p0d;
180 double minus_inf = -1.0 / p0d;
181 if (!(!signbit (255.0)
184 && (memcmp (&m0d, &p0d, sizeof (double)) == 0 || signbit (m0d))
185 && !signbit (plus_inf)
186 && signbit (minus_inf)))
192 long double plus_inf = 1.0L / p0l;
193 long double minus_inf = -1.0L / p0l;
194 if (!(!signbit (255.0L)
197 && (memcmp (&m0l, &p0l, sizeof (long double)) == 0 || signbit (m0l))
198 && !signbit (plus_inf)
199 && signbit (minus_inf)))
206 AC_DEFUN([gl_FLOAT_SIGN_LOCATION],
208 gl_FLOATTYPE_SIGN_LOCATION([float], [gl_cv_cc_float_signbit], [f], [FLT])
211 AC_DEFUN([gl_DOUBLE_SIGN_LOCATION],
213 gl_FLOATTYPE_SIGN_LOCATION([double], [gl_cv_cc_double_signbit], [], [DBL])
216 AC_DEFUN([gl_LONG_DOUBLE_SIGN_LOCATION],
218 gl_FLOATTYPE_SIGN_LOCATION([long double], [gl_cv_cc_long_double_signbit], [L], [LDBL])
221 AC_DEFUN([gl_FLOATTYPE_SIGN_LOCATION],
223 AC_CACHE_CHECK([where to find the sign bit in a '$1'],
231 ((sizeof ($1) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
232 typedef union { $1 value; unsigned int word[NWORDS]; }
234 static memory_float plus = { 1.0$3 };
235 static memory_float minus = { -1.0$3 };
240 FILE *fp = fopen ("conftest.out", "w");
243 /* Find the different bit. */
245 for (j = 0; j < NWORDS; j++)
247 unsigned int x = plus.word[j] ^ minus.word[j];
248 if ((x & (x - 1)) || (x && m))
250 /* More than one bit difference. */
251 fprintf (fp, "unknown");
263 fprintf (fp, "unknown");
266 /* Now m = plus.word[k] ^ ~minus.word[k]. */
267 if (plus.word[k] & ~minus.word[k])
269 /* Oh? The sign bit is set in the positive and cleared in the negative
271 fprintf (fp, "unknown");
277 fprintf (fp, "word %d bit %d", (int) k, (int) i);
278 return (fclose (fp) != 0);
281 [$2=`cat conftest.out`],
284 dnl When cross-compiling, we don't know. It depends on the
285 dnl ABI and compiler version. There are too many cases.
292 word=`echo "$]$2[" | sed -e 's/word //' -e 's/ bit.*//'`
293 bit=`echo "$]$2[" | sed -e 's/word.*bit //'`
294 AC_DEFINE_UNQUOTED([$4][_SIGNBIT_WORD], [$word],
295 [Define as the word index where to find the sign of '$1'.])
296 AC_DEFINE_UNQUOTED([$4][_SIGNBIT_BIT], [$bit],
297 [Define as the bit index in the word where to find the sign of '$1'.])