check_cxx_source_compiles("
    #include <langinfo.h>
    int main(int argc, char **argv)
    {
        const char *r = nl_langinfo(_NL_TIME_FIRST_WEEKDAY);
        const char *s = nl_langinfo(_NL_TIME_WEEK_1STDAY);

        return 0;
    }
" HAVE_NL_TIME_FIRST_WEEKDAY_AND_WEEK_1STDAY)