Re: tasking with GNAT 3.14p on windows

["Chad R. Meiners" <crmeiners@hotmail.com>]

"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message
news:wcck7ef9bzv.fsf@shell01.TheWorld.com...
>
> The Ada RM has nothing to say about system calls, so of course they are
> not guaranteed (by the RM) to be abortable.  But I'm very interested in
> what GNAT does with system calls in the presence of abort.  Can you tell
> us what happens if, say, a socket read is aborted?  And if it's not
> abortable, how does one work around that fact?

Ah, such a good question.  The quick answer is that one does not depend on
the use of aborts when doing socket programing ;)  Actually according to
winsock if you close the socket while another task is block on it waiting
for a read it will return a from the read function with an error.  So if you
want to shutdown you socket servers close your sockets and then abort your
tasks.

> Or suppose one task does a socket read, and another task gets aborted.
> How well does that work?  On windows, I mean.  Assume polling is turned
> on.

This works well since the tasks are mapped to native threads so the other
thread is free to poll away for the abort.  Now I must say I am by no means
an expert on the gnat compiler; my source diving has been limited to the
parser and the Text_IO implementation.  My information on tasking is based
on empirical experience, the gnat documentation and a few comments I think I
remember Dr. Dewar making on CLA ;)

-CRM