ARGF#to_a

static VALUE
argf_readlines(int argc, VALUE *argv, VALUE argf)
{
    long lineno = ARGF.lineno;
    VALUE lines, ary;

    ary = rb_ary_new();
    while (next_argv()) {
        if (ARGF_GENERIC_INPUT_P()) {
            lines = rb_funcall3(ARGF.current_file, rb_intern("readlines"), argc, argv);
        }
        else {
            lines = rb_io_readlines(argc, argv, ARGF.current_file);
            argf_close(argf);
        }
        ARGF.next_p = 1;
        rb_ary_concat(ary, lines);
        ARGF.lineno = lineno + RARRAY_LEN(ary);
        ARGF.last_lineno = ARGF.lineno;
    }
    ARGF.init_p = 0;
    return ary;
}