GNU bug report logs - #10616
flush procedure for soft ports isn't called

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From: Ian Price <ianprice90 <at> googlemail.com>
To: 10616 <at> debbugs.gnu.org
Subject: bug#10616: flush procedure for soft ports isn't called
Date: Fri, 27 Jan 2012 06:27:47 +0000

Ian Price <ianprice90 <at> googlemail.com> writes:

> Yak, this example is a horrible one, since force-output doesn't return
> the return value of the procedure anyway, but if you try replacing it
> with (lambda () (throw 'wontthrow)), and you'll see it doesn't error
>
> In sf_flush in libguile/vports.c, there is a test
>   if (pt->write_pos > pt->write_buf)
> which some printf debugging tells me is never true, in fact, those
> values never change, no matter how much I write to the port. Some food
> for thought while I grapple with how the ports code is supposed to work.

OK, so as I understand it, this is supposed to check if there has been a
write to the port. And the buffer will have at most one character in it
because it is set up that way in scm_port_non_buffer.

I notice that sf_write doesn't update this buffer, but instead just
calls the write procedure directly. In that case, it makes sense that
the value isn't changing, and therefore maybe I should just change
sf_flush into a wrapper for the flush procedure?

-- 
Ian Price

"Programming is like pinball. The reward for doing it well is
the opportunity to do it again" - from "The Wizardy Compiled"

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