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+# isinf.m4 serial 13
+dnl Copyright (C) 2007-2023 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_ISINF],
+[
+ AC_REQUIRE([gl_MATH_H_DEFAULTS])
+ AC_REQUIRE([AC_CANONICAL_HOST])
+ dnl Persuade glibc <math.h> to declare isinf.
+ AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+ AC_CHECK_DECLS([isinf], , ,
+ [[#include <math.h>
+ #ifndef isinf
+ #error "isinf must be a macro, not a function"
+ #endif
+ ]])
+ if test "$ac_cv_have_decl_isinf" = yes; then
+ gl_CHECK_MATH_LIB([ISINF_LIBM], [x = isinf (x) + isinf ((float) x);])
+ if test "$ISINF_LIBM" != missing; then
+ dnl Test whether isinf() on 'long double' works.
+ gl_ISINFL_WORKS
+ case "$gl_cv_func_isinfl_works" in
+ *yes) ;;
+ *) ISINF_LIBM=missing;;
+ esac
+ fi
+ fi
+ dnl On Solaris 10, with CC in C++ mode, isinf is not available although
+ dnl is with cc in C mode. This cannot be worked around by defining
+ dnl _XOPEN_SOURCE=600, because the latter does not work in C++ mode on
+ dnl Solaris 11.0. Therefore use the replacement functions on Solaris.
+ if test "$ac_cv_have_decl_isinf" != yes \
+ || test "$ISINF_LIBM" = missing \
+ || { case "$host_os" in solaris*) true;; *) false;; esac; }; then
+ REPLACE_ISINF=1
+ dnl No libraries are needed to link lib/isinf.c.
+ ISINF_LIBM=
+ fi
+ AC_SUBST([ISINF_LIBM])
+])
+
+dnl Test whether isinf() works:
+dnl 1) Whether it correctly returns false for LDBL_MAX.
+dnl 2) Whether on 'long double' recognizes all canonical values which are
+dnl infinite.
+AC_DEFUN([gl_ISINFL_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 isinf(long double) works], [gl_cv_func_isinfl_works],
+ [
+ AC_RUN_IFELSE(
+ [AC_LANG_SOURCE([[
+#include <float.h>
+#include <limits.h>
+#include <math.h>
+#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 (isinf (LDBL_MAX))
+ result |= 1;
+
+ {
+ memory_long_double m;
+ unsigned int i;
+
+ /* The isinf macro 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 (isinf (m.value))
+ result |= 2;
+ }
+
+#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 (isinf (x.value))
+ result |= 2;
+ }
+ {
+ /* Signalling NaN. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0xFFFF, 0x83333333, 0x00000000) };
+ if (isinf (x.value))
+ result |= 2;
+ }
+ /* isinf should return something even for noncanonical values. */
+ { /* Pseudo-NaN. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0xFFFF, 0x40000001, 0x00000000) };
+ if (isinf (x.value) && !isinf (x.value))
+ result |= 4;
+ }
+ { /* Pseudo-Infinity. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0xFFFF, 0x00000000, 0x00000000) };
+ if (isinf (x.value) && !isinf (x.value))
+ result |= 8;
+ }
+ { /* Pseudo-Zero. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0x4004, 0x00000000, 0x00000000) };
+ if (isinf (x.value) && !isinf (x.value))
+ result |= 16;
+ }
+ { /* Unnormalized number. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0x4000, 0x63333333, 0x00000000) };
+ if (isinf (x.value) && !isinf (x.value))
+ result |= 32;
+ }
+ { /* Pseudo-Denormal. */
+ static memory_long_double x =
+ { LDBL80_WORDS (0x0000, 0x83333333, 0x00000000) };
+ if (isinf (x.value) && !isinf (x.value))
+ result |= 64;
+ }
+#endif
+
+ return result;
+}]])],
+ [gl_cv_func_isinfl_works=yes],
+ [gl_cv_func_isinfl_works=no],
+ [case "$host_os" in
+ mingw*) # Guess yes on mingw, no on MSVC.
+ AC_EGREP_CPP([Known], [
+#ifdef __MINGW32__
+ Known
+#endif
+ ],
+ [gl_cv_func_isinfl_works="guessing yes"],
+ [gl_cv_func_isinfl_works="guessing no"])
+ ;;
+ *)
+ gl_cv_func_isinfl_works="guessing yes"
+ ;;
+ esac
+ ])
+ ])
+])