-# acosf.m4 serial 1
-dnl Copyright (C) 2011 Free Software Foundation, Inc.
+# acosf.m4 serial 2
+dnl Copyright (C) 2011-2012 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_REQUIRE([gl_MATH_H_DEFAULTS])
AC_REQUIRE([gl_FUNC_ACOS])
+ dnl Persuade glibc <math.h> to declare acosf().
+ AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+
dnl Test whether acosf() exists. Assume that acosf(), if it exists, is
dnl defined in the same library as acos().
save_LIBS="$LIBS"