tweak git-merge-changelog README

[gnulib.git] / m4 / modff.m4

diff --git a/m4/modff.m4 b/m4/modff.m4
index 181c406..3e78138 100644 (file)
--- a/m4/modff.m4
+++ b/m4/modff.m4
@@ -1,24 +1,93 @@
-# modff.m4 serial 1
-dnl Copyright (C) 2011 Free Software Foundation, Inc.
+# modff.m4 serial 5
+dnl Copyright (C) 2011-2014 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_MODFF],
 [
+  m4_divert_text([DEFAULTS], [gl_modff_required=plain])
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   AC_REQUIRE([gl_FUNC_MODF])
 
-  dnl Test whether modff() exists. Assume that modff(), if it exists, is
-  dnl defined in the same library as modf().
-  save_LIBS="$LIBS"
-  LIBS="$LIBS $MODF_LIBM"
-  AC_CHECK_FUNCS([modff])
-  LIBS="$save_LIBS"
-  if test $ac_cv_func_modff = yes; then
-    MODFF_LIBM="$MODF_LIBM"
+  dnl Persuade glibc <math.h> to declare modff().
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+
+  dnl Test whether modff() exists. We cannot assume that modff(), if it
+  dnl exists, is defined in the same library as modf(). This is not the case
+  dnl on FreeBSD, NetBSD, OpenBSD.
+  gl_MATHFUNC([modff], [float], [(float, float *)])
+  if test $gl_cv_func_modff_no_libm = yes \
+     || test $gl_cv_func_modff_in_libm = yes; then
+    :
+    m4_ifdef([gl_FUNC_MODFF_IEEE], [
+      if test $gl_modff_required = ieee && test $REPLACE_MODFF = 0; then
+        AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+        AC_CACHE_CHECK([whether modff works according to ISO C 99 with IEC 60559],
+          [gl_cv_func_modff_ieee],
+          [
+            save_LIBS="$LIBS"
+            LIBS="$LIBS $MODFF_LIBM"
+            AC_RUN_IFELSE(
+              [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+]gl_FLOAT_MINUS_ZERO_CODE[
+]gl_FLOAT_SIGNBIT_CODE[
+/* Compare two numbers with ==.
+   This is a separate function because IRIX 6.5 "cc -O" miscompiles an
+   'x == x' test.  */
+static int
+numeric_equal (float x, float y)
+{
+  return x == y;
+}
+static float dummy (float x, float *iptr) { return 0; }
+float zero;
+float minus_one = - 1.0f;
+int main (int argc, char *argv[])
+{
+  float (*my_modff) (float, float *) = argc ? modff : dummy;
+  int result = 0;
+  float i;
+  float f;
+  /* Test modff(NaN,...).
+     This test fails on NetBSD 5.1, OpenBSD 4.9, Solaris 9, Cygwin.  */
+  f = my_modff (zero / zero, &i);
+  if (numeric_equal (f, f))
+    result |= 1;
+  /* Test modff(-Inf,...).
+     This test fails on IRIX 6.5, OSF/1 5.1, mingw.  */
+  f = my_modff (minus_one / zero, &i);
+  if (!(f == 0.0f) || (signbitf (minus_zerof) && !signbitf (f)))
+    result |= 2;
+  return result;
+}
+              ]])],
+              [gl_cv_func_modff_ieee=yes],
+              [gl_cv_func_modff_ieee=no],
+              [case "$host_os" in
+                         # Guess yes on glibc systems.
+                 *-gnu*) gl_cv_func_modff_ieee="guessing yes" ;;
+                         # If we don't know, assume the worst.
+                 *)      gl_cv_func_modff_ieee="guessing no" ;;
+               esac
+              ])
+            LIBS="$save_LIBS"
+          ])
+        case "$gl_cv_func_modff_ieee" in
+          *yes) ;;
+          *) REPLACE_MODFF=1 ;;
+        esac
+      fi
+    ])
   else
     HAVE_MODFF=0
+  fi
+  if test $HAVE_MODFF = 0 || test $REPLACE_MODFF = 1; then
+    dnl Find libraries needed to link lib/modff.c.
     MODFF_LIBM="$MODF_LIBM"
   fi
   AC_SUBST([MODFF_LIBM])