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diff --git a/m4/isnanl.m4 b/m4/isnanl.m4
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+# isnanl.m4 serial 19
+dnl Copyright (C) 2007-2016 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_ISNANL],
+[
+ AC_REQUIRE([gl_MATH_H_DEFAULTS])
+ ISNANL_LIBM=
+ gl_HAVE_ISNANL_NO_LIBM
+ if test $gl_cv_func_isnanl_no_libm = no; then
+ gl_HAVE_ISNANL_IN_LIBM
+ if test $gl_cv_func_isnanl_in_libm = yes; then
+ ISNANL_LIBM=-lm
+ fi
+ fi
+ dnl The variable gl_func_isnanl set here is used by isnan.m4.
+ if test $gl_cv_func_isnanl_no_libm = yes \
+ || test $gl_cv_func_isnanl_in_libm = yes; then
+ save_LIBS="$LIBS"
+ LIBS="$LIBS $ISNANL_LIBM"
+ gl_FUNC_ISNANL_WORKS
+ LIBS="$save_LIBS"
+ case "$gl_cv_func_isnanl_works" in
+ *yes) gl_func_isnanl=yes ;;
+ *) gl_func_isnanl=no; ISNANL_LIBM= ;;
+ esac
+ else
+ gl_func_isnanl=no
+ fi
+ if test $gl_func_isnanl != yes; then
+ HAVE_ISNANL=0
+ fi
+ AC_SUBST([ISNANL_LIBM])
+])
+
+AC_DEFUN([gl_FUNC_ISNANL_NO_LIBM],
+[
+ gl_HAVE_ISNANL_NO_LIBM
+ gl_func_isnanl_no_libm=$gl_cv_func_isnanl_no_libm
+ if test $gl_func_isnanl_no_libm = yes; then
+ gl_FUNC_ISNANL_WORKS
+ case "$gl_cv_func_isnanl_works" in
+ *yes) ;;
+ *) gl_func_isnanl_no_libm=no ;;
+ esac
+ fi
+ if test $gl_func_isnanl_no_libm = yes; then
+ AC_DEFINE([HAVE_ISNANL_IN_LIBC], [1],
+ [Define if the isnan(long double) function is available in libc.])
+ fi
+])
+
+dnl Prerequisites of replacement isnanl definition. It does not need -lm.
+AC_DEFUN([gl_PREREQ_ISNANL],
+[
+ gl_LONG_DOUBLE_EXPONENT_LOCATION
+ AC_REQUIRE([gl_LONG_DOUBLE_VS_DOUBLE])
+])
+
+dnl Test whether isnanl() can be used without libm.
+AC_DEFUN([gl_HAVE_ISNANL_NO_LIBM],
+[
+ AC_CACHE_CHECK([whether isnan(long double) can be used without linking with libm],
+ [gl_cv_func_isnanl_no_libm],
+ [
+ AC_LINK_IFELSE(
+ [AC_LANG_PROGRAM(
+ [[#include <math.h>
+ #if __GNUC__ >= 4
+ # undef isnanl
+ # define isnanl(x) __builtin_isnanl ((long double)(x))
+ #elif defined isnan
+ # undef isnanl
+ # define isnanl(x) isnan ((long double)(x))
+ #endif
+ long double x;]],
+ [[return isnanl (x);]])],
+ [gl_cv_func_isnanl_no_libm=yes],
+ [gl_cv_func_isnanl_no_libm=no])
+ ])
+])
+
+dnl Test whether isnanl() can be used with libm.
+AC_DEFUN([gl_HAVE_ISNANL_IN_LIBM],
+[
+ AC_CACHE_CHECK([whether isnan(long double) can be used with libm],
+ [gl_cv_func_isnanl_in_libm],
+ [
+ save_LIBS="$LIBS"
+ LIBS="$LIBS -lm"
+ AC_LINK_IFELSE(
+ [AC_LANG_PROGRAM(
+ [[#include <math.h>
+ #if __GNUC__ >= 4
+ # undef isnanl
+ # define isnanl(x) __builtin_isnanl ((long double)(x))
+ #elif defined isnan
+ # undef isnanl
+ # define isnanl(x) isnan ((long double)(x))
+ #endif
+ long double x;]],
+ [[return isnanl (x);]])],
+ [gl_cv_func_isnanl_in_libm=yes],
+ [gl_cv_func_isnanl_in_libm=no])
+ LIBS="$save_LIBS"
+ ])
+])
+
+dnl Test whether isnanl() recognizes all canonical numbers which are neither
+dnl finite nor infinite.
+AC_DEFUN([gl_FUNC_ISNANL_WORKS],
+[
+ AC_REQUIRE([AC_PROG_CC])
+ AC_REQUIRE([gl_BIGENDIAN])
+ AC_REQUIRE([gl_LONG_DOUBLE_VS_DOUBLE])
+ AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+ AC_CACHE_CHECK([whether isnanl works], [gl_cv_func_isnanl_works],
+ [
+ AC_RUN_IFELSE(
+ [AC_LANG_SOURCE([[
+#include <float.h>
+#include <limits.h>
+#include <math.h>
+#if __GNUC__ >= 4
+# undef isnanl
+# define isnanl(x) __builtin_isnanl ((long double)(x))
+#elif defined isnan
+# undef isnanl
+# define isnanl(x) isnan ((long double)(x))
+#endif
+#define NWORDS \
+ ((sizeof (long double) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
+typedef union { unsigned int word[NWORDS]; long double value; }
+ memory_long_double;
+/* On Irix 6.5, gcc 3.4.3 can't compute compile-time NaN, and needs the
+ runtime type conversion. */
+#ifdef __sgi
+static long double NaNl ()
+{
+ double zero = 0.0;
+ return zero / zero;
+}
+#else
+# define NaNl() (0.0L / 0.0L)
+#endif
+int main ()
+{
+ int result = 0;
+
+ if (!isnanl (NaNl ()))
+ result |= 1;
+
+ {
+ memory_long_double m;
+ unsigned int i;
+
+ /* The isnanl function should be immune against changes in the sign bit and
+ in the mantissa bits. The xor operation twiddles a bit that can only be
+ a sign bit or a mantissa bit (since the exponent never extends to
+ bit 31). */
+ m.value = NaNl ();
+ m.word[NWORDS / 2] ^= (unsigned int) 1 << (sizeof (unsigned int) * CHAR_BIT - 1);
+ for (i = 0; i < NWORDS; i++)
+ m.word[i] |= 1;
+ if (!isnanl (m.value))
+ result |= 1;
+ }
+
+#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
+/* Representation of an 80-bit 'long double' as an initializer for a sequence
+ of 'unsigned int' words. */
+# ifdef WORDS_BIGENDIAN
+# define LDBL80_WORDS(exponent,manthi,mantlo) \
+ { ((unsigned int) (exponent) << 16) | ((unsigned int) (manthi) >> 16), \
+ ((unsigned int) (manthi) << 16) | ((unsigned int) (mantlo) >> 16), \
+ (unsigned int) (mantlo) << 16 \
+ }
+# else
+# define LDBL80_WORDS(exponent,manthi,mantlo) \
+ { mantlo, manthi, exponent }
+# endif
+ { /* Quiet NaN. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0xFFFF, 0xC3333333, 0x00000000) };
+ if (!isnanl (x.value))
+ result |= 2;
+ }
+ {
+ /* Signalling NaN. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0xFFFF, 0x83333333, 0x00000000) };
+ if (!isnanl (x.value))
+ result |= 2;
+ }
+ /* isnanl should return something even for noncanonical values. */
+ { /* Pseudo-NaN. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0xFFFF, 0x40000001, 0x00000000) };
+ if (isnanl (x.value) && !isnanl (x.value))
+ result |= 4;
+ }
+ { /* Pseudo-Infinity. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0xFFFF, 0x00000000, 0x00000000) };
+ if (isnanl (x.value) && !isnanl (x.value))
+ result |= 8;
+ }
+ { /* Pseudo-Zero. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0x4004, 0x00000000, 0x00000000) };
+ if (isnanl (x.value) && !isnanl (x.value))
+ result |= 16;
+ }
+ { /* Unnormalized number. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0x4000, 0x63333333, 0x00000000) };
+ if (isnanl (x.value) && !isnanl (x.value))
+ result |= 32;
+ }
+ { /* Pseudo-Denormal. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0x0000, 0x83333333, 0x00000000) };
+ if (isnanl (x.value) && !isnanl (x.value))
+ result |= 64;
+ }
+#endif
+
+ return result;
+}]])],
+ [gl_cv_func_isnanl_works=yes],
+ [gl_cv_func_isnanl_works=no],
+ [gl_cv_func_isnanl_works="guessing yes"])
+ ])
+])