gettimeofday: port recent C++ fix to Emacs

[gnulib.git] / m4 / modff.m4

diff --git a/m4/modff.m4 b/m4/modff.m4
index 3b117ec..9813b61 100644 (file)
--- a/m4/modff.m4
+++ b/m4/modff.m4
@@ -1,5 +1,5 @@
-# modff.m4 serial 3
-dnl Copyright (C) 2011-2012 Free Software Foundation, Inc.
+# modff.m4 serial 5
+dnl Copyright (C) 2011-2013 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.
@@ -10,6 +10,9 @@ AC_DEFUN([gl_FUNC_MODFF],
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   AC_REQUIRE([gl_FUNC_MODF])
 
+  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.
@@ -19,6 +22,7 @@ AC_DEFUN([gl_FUNC_MODFF],
     :
     m4_ifdef([gl_FUNC_MODFF_IEEE], [
       if test $gl_modff_required = ieee && test $REPLACE_MODFF = 0; then
+        AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
         AC_CACHE_CHECK([whether modff works according to ISO C 99 with IEC 60559],
           [gl_cv_func_modff_ieee],
           [
@@ -64,7 +68,13 @@ int main (int argc, char *argv[])
               ]])],
               [gl_cv_func_modff_ieee=yes],
               [gl_cv_func_modff_ieee=no],
-              [gl_cv_func_modff_ieee="guessing no"])
+              [case "$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