On 23 Jun 2010, at 11:47, Ben Haller wrote:
> On 23-Jun-10, at 6:22 AM, Uli Kusterer wrote:
>
>> Am Jun 23, 2010 um 12:14 PM schrieb Ben Haller:
>>> So I have a workaround for the problem, but I want to understand *why* it
>>> works. Shouldn't NSPipe close its associated files when it deallocs? Why
>>> should it be necessary to call -closeFile? This behavior seems to be
>>> specifically contradicted by the documentation on NSPipe, which says (in
>>> -fileHandleForReading) "The descriptor represented by this object is
>>> deleted, and the object itself is automatically deallocated when the
>>> receiver is deallocated." Well, when my NSPipes are deallocated, the file
>>> handles are indeed automatically deallocated (a funny way to put it), but
>>> the descriptor is *not* deleted. Is this a bug? More likely I'm
>>> misunderstanding something; can anybody clarify this for me?
>>
>> AFAIR, NSPipe autoreleases its NSFileHandles), which means even if you give
>> up all your references to the pipe, it won't automatically close everything
>> until the current autorelease pool gets popped. While closeFile doesn't get
>> rid of the objects, it forces the file handle to be closed, which is why it
>> solves your immediate problem.
>>
>> If you're running your own loop where you create and tear down lots of
>> pipes, it might help to just create your own autorelease pool inside the
>> loop on each iteration.
>
> Yes; this is not an autorelease pool problem, however, as I described in my
> original post. The run loop is running freely, and the pipes and file
> handles are in fact getting dealloced; I have confirmed this explicitly in
> Instruments. And yet, the file descriptors don't get deleted unless I
> explicitly call -closeFile. That's the mystery (or is it a bug?).
>
To me it seems pretty explicit in the NSPipe docs
http://developer.apple.com/mac/library/documentation/cocoa/reference/foundation/Classes/NSPipe_Class/Reference/Reference.html#//apple_ref/occ/instm/NSPipe/fileHandleForWriting
fileHandleForReading
You use the returned file handle to read from the pipe using NSFileHandle's
read methods—availableData,readDataToEndOfFile, and readDataOfLength:.
You don’t need to send closeFile to this object or explicitly release the
object after you have finished using it.
fileHandleForWriting
You use the returned file handle to write to the pipe using NSFileHandle's
writeData: method. When you are finished writing data to this object, send it a
closeFile message to delete the descriptor. Deleting the descriptor causes the
reading process to receive an end-of-data signal (an empty NSData object).
So you can dispense with closeFile on the read handle.
Regards
Jonathan Mitchell
Developer
Mugginsoft LLP
http://www.mugginsoft.com
> Ben Haller
> McGill University
>
>
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