Re: I/O - exception handling

["Randy Brukardt" <randy@rrsoftware.com>]

Robert I. Eachus wrote in message <3EDA24D2.6060003@attbi.com>...
>Randy Brukardt wrote:
>
>> It wouldn't be *expected*, but the standard *allows* it, so the truly
>> paranoid programmer would have to take that into account. And even if
>> you defined it not to raise any IO_Exceptions, it still could raise
>> Storage_Error or Program_Error, so you can't claim that it never,
ever
>> raised any exceptions anyway.
>>
>> As I said, its not worth worrying about; in practice, it won't raise
an
>> exception, and there is no need to protect it. But you can't
determine
>> that from the standard (and there is no possible standard language
from
>> which you could).
>
>At the risk of being repitious there are cases in Ada where unusual
>behavior can be associated with particular file types.  A good example
I
>ran into years ago was an OS where opening a pipe required a special
>call that returned two file descriptors, and only the first (the write
>end) could be closed, which closed the whole pipe.  An excellent
example
>of where a call to Close should raise Use_Error.  But notice that
>opening the pipe took a non-standard Open call.


Of course, but the question I was answering was about Is_Open, not
Close. I would give different advice about Close, for the reasons you
give. But a compiler raising Use_Error on Is_Open would be pretty weird
(and unhelpful).

                Randy.