Re: File descriptors not freed up without a -closeFile call
Re: File descriptors not freed up without a -closeFile call
- Subject: Re: File descriptors not freed up without a -closeFile call
- From: Ben Haller <email@hidden>
- Date: Wed, 23 Jun 2010 06:47:34 -0400
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?).
Ben Haller
McGill University
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