1 # isfinite.m4 serial 16
2 dnl Copyright (C) 2007-2017 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.
7 AC_DEFUN([gl_ISFINITE],
9 AC_REQUIRE([gl_MATH_H_DEFAULTS])
10 dnl Persuade glibc <math.h> to declare isfinite.
11 AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
12 AC_CHECK_DECLS([isfinite], , , [[#include <math.h>]])
13 if test "$ac_cv_have_decl_isfinite" = yes; then
14 gl_CHECK_MATH_LIB([ISFINITE_LIBM],
15 [x = isfinite (x) + isfinite ((float) x);])
16 if test "$ISFINITE_LIBM" != missing; then
17 dnl Test whether isfinite() on 'long double' works.
19 case "$gl_cv_func_isfinitel_works" in
21 *) ISFINITE_LIBM=missing;;
23 dnl Also, isfinite() on 'double' does not work on Linux/ia64 (because of
24 dnl signalling NaNs). But this does not have to be tested, since
25 dnl isfinite(long double) also does not work in this situation.
28 if test "$ac_cv_have_decl_isfinite" != yes ||
29 test "$ISFINITE_LIBM" = missing; then
31 dnl No libraries are needed to link lib/isfinite.c.
34 AC_SUBST([ISFINITE_LIBM])
37 dnl Test whether isfinite() on 'long double' recognizes all canonical values
38 dnl which are neither finite nor infinite.
39 AC_DEFUN([gl_ISFINITEL_WORKS],
41 AC_REQUIRE([AC_PROG_CC])
42 AC_REQUIRE([gl_BIGENDIAN])
43 AC_REQUIRE([gl_LONG_DOUBLE_VS_DOUBLE])
44 AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
45 AC_CACHE_CHECK([whether isfinite(long double) works], [gl_cv_func_isfinitel_works],
47 AC_RUN_IFELSE([AC_LANG_SOURCE([[
52 ((sizeof (long double) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
53 typedef union { unsigned int word[NWORDS]; long double value; }
55 /* On Irix 6.5, gcc 3.4.3 can't compute compile-time NaN, and needs the
56 runtime type conversion. */
58 static long double NaNl ()
64 # define NaNl() (0.0L / 0.0L)
74 /* The isfinite macro should be immune against changes in the sign bit and
75 in the mantissa bits. The xor operation twiddles a bit that can only be
76 a sign bit or a mantissa bit (since the exponent never extends to
79 m.word[NWORDS / 2] ^= (unsigned int) 1 << (sizeof (unsigned int) * CHAR_BIT - 1);
80 for (i = 0; i < NWORDS; i++)
82 if (isfinite (m.value))
86 #if ((defined __ia64 && LDBL_MANT_DIG == 64) || (defined __x86_64__ || defined __amd64__) || (defined __i386 || defined __i386__ || defined _I386 || defined _M_IX86 || defined _X86_)) && !HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
87 /* Representation of an 80-bit 'long double' as an initializer for a sequence
88 of 'unsigned int' words. */
89 # ifdef WORDS_BIGENDIAN
90 # define LDBL80_WORDS(exponent,manthi,mantlo) \
91 { ((unsigned int) (exponent) << 16) | ((unsigned int) (manthi) >> 16), \
92 ((unsigned int) (manthi) << 16) | ((unsigned int) (mantlo) >> 16), \
93 (unsigned int) (mantlo) << 16 \
96 # define LDBL80_WORDS(exponent,manthi,mantlo) \
97 { mantlo, manthi, exponent }
100 static memory_long_double x =
101 { LDBL80_WORDS (0xFFFF, 0xC3333333, 0x00000000) };
102 if (isfinite (x.value))
106 /* Signalling NaN. */
107 static memory_long_double x =
108 { LDBL80_WORDS (0xFFFF, 0x83333333, 0x00000000) };
109 if (isfinite (x.value))
112 /* isfinite should return something even for noncanonical values. */
114 static memory_long_double x =
115 { LDBL80_WORDS (0xFFFF, 0x40000001, 0x00000000) };
116 if (isfinite (x.value) && !isfinite (x.value))
119 { /* Pseudo-Infinity. */
120 static memory_long_double x =
121 { LDBL80_WORDS (0xFFFF, 0x00000000, 0x00000000) };
122 if (isfinite (x.value) && !isfinite (x.value))
126 static memory_long_double x =
127 { LDBL80_WORDS (0x4004, 0x00000000, 0x00000000) };
128 if (isfinite (x.value) && !isfinite (x.value))
131 { /* Unnormalized number. */
132 static memory_long_double x =
133 { LDBL80_WORDS (0x4000, 0x63333333, 0x00000000) };
134 if (isfinite (x.value) && !isfinite (x.value))
137 { /* Pseudo-Denormal. */
138 static memory_long_double x =
139 { LDBL80_WORDS (0x0000, 0x83333333, 0x00000000) };
140 if (isfinite (x.value) && !isfinite (x.value))
147 [gl_cv_func_isfinitel_works=yes],
148 [gl_cv_func_isfinitel_works=no],
150 # Guess no on native Windows.
151 mingw*) gl_cv_func_isfinitel_works="guessing no" ;;
152 *) gl_cv_func_isfinitel_works="guessing yes" ;;