ansi-c++-opt: Provide option --enable-c++/--disable-c++ when possible.

[gnulib.git] / m4 / frexp.m4

diff --git a/m4/frexp.m4 b/m4/frexp.m4
index 60d897b..1f6d542 100644 (file)
--- a/m4/frexp.m4
+++ b/m4/frexp.m4
@@ -1,5 +1,5 @@
-# frexp.m4 serial 1
-dnl Copyright (C) 2007 Free Software Foundation, Inc.
+# frexp.m4 serial 8
+dnl Copyright (C) 2007-2010 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.
@@ -7,16 +7,8 @@ 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=
-  AC_CACHE_CHECK([whether frexp() can be used without linking with libm],
-    [gl_cv_func_frexp_no_libm],
-    [
-      AC_TRY_LINK([#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])
-    ])
   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],
@@ -48,15 +40,55 @@ AC_DEFUN([gl_FUNC_FREXP],
     gl_func_frexp=no
   fi
   if test $gl_func_frexp = yes; then
-    AC_DEFINE([HAVE_FREXP], 1,
+    AC_DEFINE([HAVE_FREXP], [1],
       [Define if the frexp() function is available and works.])
   else
     AC_LIBOBJ([frexp])
   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.])
+  else
+    AC_LIBOBJ([frexp])
+  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_TRY_LINK([#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.
-dnl This test fails e.g. on NetBSD.
+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).
 AC_DEFUN([gl_FUNC_FREXP_WORKS],
 [
   AC_REQUIRE([AC_PROG_CC])
@@ -66,10 +98,15 @@ AC_DEFUN([gl_FUNC_FREXP_WORKS],
       AC_TRY_RUN([
 #include <float.h>
 #include <math.h>
+#include <string.h>
 int main()
 {
   int i;
   volatile double x;
+/* HP cc on HP-UX 10.20 has a bug with the constant expression -0.0.
+   So we use -zero instead.  */
+  double zero = 0.0;
+  /* Test on denormalized numbers.  */
   for (i = 1, x = 1.0; i >= DBL_MIN_EXP; i--, x *= 0.5)
     ;
   if (x > 0.0)
@@ -81,11 +118,27 @@ int main()
       if (y != 0.5)
         return 1;
     }
+  /* Test on infinite numbers.  */
+  x = 1.0 / 0.0;
+  {
+    int exp;
+    double y = frexp (x, &exp);
+    if (y != x)
+      return 1;
+  }
+  /* Test on negative zero.  */
+  x = -zero;
+  {
+    int exp;
+    double y = frexp (x, &exp);
+    if (memcmp (&y, &x, sizeof x))
+      return 1;
+  }
   return 0;
 }], [gl_cv_func_frexp_works=yes], [gl_cv_func_frexp_works=no],
       [case "$host_os" in
-         netbsd*) gl_cv_func_frexp_works="guessing no";;
-         *)       gl_cv_func_frexp_works="guessing yes";;
+         netbsd* | irix* | mingw*) gl_cv_func_frexp_works="guessing no";;
+         *)                        gl_cv_func_frexp_works="guessing yes";;
        esac
       ])
     ])