1 files changed, 181 insertions, 0 deletions
diff --git a/m4/frexp.m4 b/m4/frexp.m4
new file mode 100644
index 0000000..5d977d4
--- /dev/null
+++ b/m4/frexp.m4
@@ -0,0 +1,181 @@
+# frexp.m4 serial 16
+dnl Copyright (C) 2007-2020 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_FREXP],
+[
+  AC_REQUIRE([gl_MATH_H_DEFAULTS])
+  AC_REQUIRE([gl_CHECK_FREXP_NO_LIBM])
+  FREXP_LIBM=
+  if test $gl_cv_func_frexp_no_libm = no; then
+    AC_CACHE_CHECK([whether frexp() can be used with libm],
+      [gl_cv_func_frexp_in_libm],
+      [
+        save_LIBS="$LIBS"
+        LIBS="$LIBS -lm"
+        AC_LINK_IFELSE(
+          [AC_LANG_PROGRAM(
+             [[#include <math.h>
+               double x;]],
+             [[int e; return frexp (x, &e) > 0;]])],
+          [gl_cv_func_frexp_in_libm=yes],
+          [gl_cv_func_frexp_in_libm=no])
+        LIBS="$save_LIBS"
+      ])
+    if test $gl_cv_func_frexp_in_libm = yes; then
+      FREXP_LIBM=-lm
+    fi
+  fi
+  if test $gl_cv_func_frexp_no_libm = yes \
+     || test $gl_cv_func_frexp_in_libm = yes; then
+    save_LIBS="$LIBS"
+    LIBS="$LIBS $FREXP_LIBM"
+    gl_FUNC_FREXP_WORKS
+    LIBS="$save_LIBS"
+    case "$gl_cv_func_frexp_works" in
+      *yes) gl_func_frexp=yes ;;
+      *)    gl_func_frexp=no; REPLACE_FREXP=1; FREXP_LIBM= ;;
+    esac
+  else
+    gl_func_frexp=no
+  fi
+  if test $gl_func_frexp = yes; then
+    AC_DEFINE([HAVE_FREXP], [1],
+      [Define if the frexp() function is available and works.])
+  fi
+  AC_SUBST([FREXP_LIBM])
+])
+
+AC_DEFUN([gl_FUNC_FREXP_NO_LIBM],
+[
+  AC_REQUIRE([gl_MATH_H_DEFAULTS])
+  AC_REQUIRE([gl_CHECK_FREXP_NO_LIBM])
+  if test $gl_cv_func_frexp_no_libm = yes; then
+    gl_FUNC_FREXP_WORKS
+    case "$gl_cv_func_frexp_works" in
+      *yes) gl_func_frexp_no_libm=yes ;;
+      *)    gl_func_frexp_no_libm=no; REPLACE_FREXP=1 ;;
+    esac
+  else
+    gl_func_frexp_no_libm=no
+    dnl Set REPLACE_FREXP here because the system may have frexp in libm.
+    REPLACE_FREXP=1
+  fi
+  if test $gl_func_frexp_no_libm = yes; then
+    AC_DEFINE([HAVE_FREXP_IN_LIBC], [1],
+      [Define if the frexp() function is available in libc.])
+  fi
+])
+
+dnl Test whether frexp() can be used without linking with libm.
+dnl Set gl_cv_func_frexp_no_libm to 'yes' or 'no' accordingly.
+AC_DEFUN([gl_CHECK_FREXP_NO_LIBM],
+[
+  AC_CACHE_CHECK([whether frexp() can be used without linking with libm],
+    [gl_cv_func_frexp_no_libm],
+    [
+      AC_LINK_IFELSE(
+        [AC_LANG_PROGRAM(
+           [[#include <math.h>
+             double x;]],
+           [[int e; return frexp (x, &e) > 0;]])],
+        [gl_cv_func_frexp_no_libm=yes],
+        [gl_cv_func_frexp_no_libm=no])
+    ])
+])
+
+dnl Test whether frexp() works also on denormalized numbers (this fails e.g. on
+dnl NetBSD 3.0), on infinite numbers (this fails e.g. on IRIX 6.5 and mingw),
+dnl and on negative zero (this fails e.g. on NetBSD 4.99 and mingw).
+AC_DEFUN([gl_FUNC_FREXP_WORKS],
+[
+  AC_REQUIRE([AC_PROG_CC])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  AC_CHECK_DECLS_ONCE([alarm])
+  AC_CACHE_CHECK([whether frexp works], [gl_cv_func_frexp_works],
+    [
+      AC_RUN_IFELSE(
+        [AC_LANG_SOURCE([[
+#include <float.h>
+#include <math.h>
+#include <string.h>
+#if HAVE_DECL_ALARM
+# include <signal.h>
+# include <unistd.h>
+#endif
+/* HP cc on HP-UX 10.20 has a bug with the constant expression -0.0.
+   ICC 10.0 has a bug when optimizing the expression -zero.
+   The expression -DBL_MIN * DBL_MIN does not work when cross-compiling
+   to PowerPC on Mac OS X 10.5.  */
+#if defined __hpux || defined __sgi || defined __ICC
+static double
+compute_minus_zero (void)
+{
+  return -DBL_MIN * DBL_MIN;
+}
+# define minus_zero compute_minus_zero ()
+#else
+double minus_zero = -0.0;
+#endif
+int main()
+{
+  int result = 0;
+  int i;
+  volatile double x;
+  double zero = 0.0;
+#if HAVE_DECL_ALARM
+  /* NeXTstep 3.3 frexp() runs into an endless loop when called on an infinite
+     number.  Let the test fail in this case.  */
+  signal (SIGALRM, SIG_DFL);
+  alarm (5);
+#endif
+  /* Test on denormalized numbers.  */
+  for (i = 1, x = 1.0; i >= DBL_MIN_EXP; i--, x *= 0.5)
+    ;
+  if (x > 0.0)
+    {
+      int exp;
+      double y = frexp (x, &exp);
+      /* On machines with IEEE754 arithmetic: x = 1.11254e-308, exp = -1022.
+         On NetBSD: y = 0.75. Correct: y = 0.5.  */
+      if (y != 0.5)
+        result |= 1;
+    }
+  /* Test on infinite numbers.  */
+  x = 1.0 / zero;
+  {
+    int exp;
+    double y = frexp (x, &exp);
+    if (y != x)
+      result |= 2;
+  }
+  /* Test on negative zero.  */
+  x = minus_zero;
+  {
+    int exp;
+    double y = frexp (x, &exp);
+    if (memcmp (&y, &x, sizeof x))
+      result |= 4;
+  }
+  return result;
+}]])],
+        [gl_cv_func_frexp_works=yes],
+        [gl_cv_func_frexp_works=no],
+        [case "$host_os" in
+           netbsd* | irix*) gl_cv_func_frexp_works="guessing no" ;;
+           mingw*) # Guess yes with MSVC, no with mingw.
+             AC_EGREP_CPP([Good], [
+#ifdef _MSC_VER
+ Good
+#endif
+               ],
+               [gl_cv_func_frexp_works="guessing yes"],
+               [gl_cv_func_frexp_works="guessing no"])
+             ;;
+           *) gl_cv_func_frexp_works="guessing yes" ;;
+         esac
+        ])
+    ])
+])