Re: [Chicken-users] a couple of questions about foreign functions (Modified by Valentyn Kamyshenko)

[Felix Winkelmann]

Am Thu, 22 Jan 2004 01:51:38 -0800 hat Valentyn Kamyshenko 
<address@hidden> geschrieben:

> In general, IMHO, it is a serious problem. I personally would rather 
> prefer to live without threads (and without functionality that requires 
> them in chicken), but to have standard signal handling, use blocking I/O 
> calls in foreign functions etc.

That's understandable, but IMHO the whole idea of UNIX signals is something
that I consider somewhat broken. A signal handler can be called at any 
time,
completely out of context. This is not compatible with the execution model
that Chicken uses (unfortunately).

>  Probably, a compiler option? Is it achievable at all?

You mean a mode where signals may trigger Scheme signal handlers, even
in a blocking I/O operation, right?

Hmmm... Generally it should be possible to perform an out-of-context
call inside a signal handler (comparable to the way callbacks are 
handled),
but IIRC there exist some restrictions on what system calls may be
invoked inside of a signal handler. So the signal handler should only
set some flag (indicating a pending signal) and then abort the I/O
operation in progress, which then should return to the caller and
let the usual interrupt-processing behaviour take place.

Is it possible in UNIX to abort a currently blocking I/O operation,
given a file-descriptor?


cheers,
felix