basic_quote_characters=

static VALUE
readline_s_set_basic_quote_characters(VALUE self, VALUE str)
{
    static char *basic_quote_characters = NULL;

    rb_secure(4);
    OutputStringValue(str);
    if (basic_quote_characters == NULL) {
        basic_quote_characters =
            ALLOC_N(char, RSTRING_LEN(str) + 1);
    }
    else {
        REALLOC_N(basic_quote_characters, char, RSTRING_LEN(str) + 1);
    }
    strncpy(basic_quote_characters,
            RSTRING_PTR(str), RSTRING_LEN(str));
    basic_quote_characters[RSTRING_LEN(str)] = '\0';
    rl_basic_quote_characters = basic_quote_characters;

    return self;
}