Re: Hang during AESend
Re: Hang during AESend
- Subject: Re: Hang during AESend
- From: Trygve Inda <email@hidden>
- Date: Tue, 13 May 2014 21:03:54 -0700
- Thread-topic: Hang during AESend
> On May 13, 2014, at 13:03 , Trygve Inda <email@hidden> wrote:
>
>> NSAppleEventDescriptor *appleEvent = [NSAppleEventDescriptor
>> appleEventWithEventClass: kMyAEClass
>> eventID: kMyAEEventID
>> targetDescriptor: targetDescriptor
>> returnID: kAutoGenerateReturnID
>> transactionID: kAnyTransactionID];
>
>> AESendMessage([appleEvent aeDesc], NULL, kAENoReply | kAENeverInteract,
>> kAEDefaultTimeout);
>
> What memory model? ARC?
>
> You’re getting back back a NSAppleEventDescriptor with +0 semantics, which
> means (if ARC) it’s going to be locally retained, then released when it goes
> out of scope (possibly a scope optimized optimized to the last reference).
>
> What you’re passing to AESendMessage is an interior pointer (‘aeDesc’ is
> marked NS_RETURNS_INNER_POINTER in the headers). AFAIK that keeps the
> underlying object alive *in the calling code* long enough for the interior
> pointer to be passed safely into the called function, but no longer.
>
> In particular, I don’t know that the interior pointer can be assumed to be
> valid for the entire length of the called function’s execution. Of course,
> there’d have to be asynchronous activity (or perhaps a autorelease pool drain
> inside the called function) for this to matter, but since you’re not asking
> for a reply, that seems possible.
>
> So, my theory: memory management bug in your code. A simple way to test this
> would be to put ‘[appleEvent self];’ after the AESendMessage call, and see if
> the problem goes away.
>
One thing I have noticed...
I am calling AESendMessage to send a new AppleEvent from a handler for
another AppleEvent
Eg in the handler for event of type EventA, I am using AESendMessage to send
EventB
If instead I use an NSOperationQueue to send EventB (adding a operation to
the queue in the responder for EventA), then everything works.
I am guessing that AESendMessage does not like being called from within an
AppleEvent handler, but it works most of the time so I am not sure.
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