AC_DEFUN([AC_VAR_TIMEZONE_EXTERNALS],
[ AC_REQUIRE([AC_STRUCT_TIMEZONE])dnl
AC_CACHE_CHECK(for timezone external, mb_cv_var_timezone,
[ AC_TRY_LINK([#include <time.h>], [return (int)timezone;],
mb_cv_var_timezone=yes,
mb_cv_var_timezone=no)
])
AC_CACHE_CHECK(for altzone external, mb_cv_var_altzone,
[ AC_TRY_LINK([#include <time.h>], [return (int)altzone;],
mb_cv_var_altzone=yes,
mb_cv_var_altzone=no)
])
AC_CACHE_CHECK(for daylight external, mb_cv_var_daylight,
[ AC_TRY_LINK([#include <time.h>], [return (int)daylight;],
mb_cv_var_daylight=yes,
mb_cv_var_daylight=no)
])
if test $mb_cv_var_timezone = yes; then
AC_DEFINE([HAVE_TIMEZONE], 1,
[Define if you have the external `timezone' variable.])
fi
if test $mb_cv_var_altzone = yes; then
AC_DEFINE([HAVE_ALTZONE], 1,
[Define if you have the external `altzone' variable.])
fi
if test $mb_cv_var_daylight = yes; then
AC_DEFINE([HAVE_DAYLIGHT], 1,
[Define if you have the external `daylight' variable.])
fi
])