Comment by dooglius

Some commenters are claiming this issue can be worked around by using by-reference capture, but the following code still requires dynamic allocation:

  void reverse_bitstream(void * read_ctx, void * write_ctx) {
    guard {
      while(has_more_bits(read_ctx)) {
        int b = read_bit(read_ctx);
        if     (b == 0) defer write_bit(write_ctx, 0);
        else if(b == 1) defer write_bit(write_ctx, 1);
      }
    }
  }