Re: Implementing R6RS `transcoded-port'

[Andreas Rottmann <a.rottmann@gmx.at>]

Thien-Thi Nguyen <ttn@gnuvola.org> writes:

> () Andreas Rottmann <a.rottmann@gmx.at>
> () Sun, 25 Jul 2010 21:12:22 +0200
>
>        result_pt->file_name = pt->file_name;
>        result_pt->line_number = pt->line_number;
>        result_pt->column_number = pt->column_number;
>
>        result_pt->read_buf = pt->read_buf;
>        result_pt->read_pos = pt->read_pos;
>        result_pt->read_end = pt->read_end;
>        result_pt->read_buf_size = pt->read_buf_size;
>
>        result_pt->saved_read_buf = pt->saved_read_buf;
>        result_pt->saved_read_pos = pt->saved_read_pos;
>        result_pt->saved_read_end = pt->saved_read_end;
>        result_pt->saved_read_buf_size = pt->saved_read_buf_size;
>
>        result_pt->write_buf = pt->write_buf;
>        result_pt->write_pos = pt->write_pos;
>        result_pt->write_end = pt->write_end;
>        result_pt->write_buf_size = pt->write_buf_size;
>
>        result_pt->shortbuf = pt->shortbuf;
>        result_pt->rw_random = pt->rw_random;
>        result_pt->rw_active = pt->rw_active;
>        result_pt->putback_buf = pt->putback_buf;
>        result_pt->putback_buf_size = pt->putback_buf_size; 
>
>        scm_i_remove_port (port);
>        SCM_CLR_PORT_OPEN_FLAG (port);
>
> Most likely ‘scm_i_remove_port’ arranges to clean up pt->FOO, so ‘gc’
> ends up leaving some these assigned members (result_pt->FOO) pointing to
> "valid" memory with invalid contents.  For those, a pointer copy is
> insufficient; you need to copy their contents to newly allocated memory.
>
I thought along these lines as well, but it seems the whole memory area
pointed to by `result_pt' is set to zero somewhere during
GC. Additionally, removing the call to `scm_i_remove_port' doesn't
change this.

Regards, Rotty
-- 
Andreas Rottmann -- <http://rotty.yi.org/>