[Info-vax] yet another sys$qiow question

[JF Mezei]

On 15-08-22 15:36, David Froble wrote:

> If you're going to exit a routine that queued up a QIO, or other async service, 
> before the operation is complete, then don't cha think that cancelling the thing 
> might be the thing to do? 

No reason to cancel it if the buffer and IOSB blocks are allocated in
heap or in stack of the calling routine. (aka. exiting the routine won't
cause those variables to be de-allocated and returned to stack).



> If I remember correctly, and no, I haven't done much 
> of this, the AST would then never be queued.  Nor should it.
> 
> If I remember correctly,


My recollection is that $CANCEL will still cause the AST for the QIO to
be delivered, but the IOSB will show the IO was cancelled.  I could be
wrong (as I often am).

When I have code that does both timer and QIO, (with the timer AST
issuing a $CANCEL for the QIO), the QIO AST checked for a "CANCELLED"
status code.