source_release_column (col->source, col->byte_ofs, col->width);
allocate_column (ds, new_width, col);
value_init (&src, old_width);
value_init (&dst, new_width);
source_release_column (col->source, col->byte_ofs, col->width);
allocate_column (ds, new_width, col);
value_init (&src, old_width);
value_init (&dst, new_width);