Thank you, Dave!

I now understand that going through CommandShell was the sanctioned
way of using PipeableOSProcess.  I'll just modify our code to close it
explicitly.  (And it seems to work beter.)

I tried clearing the allMyChildren directory but did not seem to free
these fds.  I tried:

PipeableOSProcess allSubInstancesDo: [:e | e closePipes]

but this do it seems to kill the VM.

-- Yoshiki

At Wed, 16 May 2012 15:33:39 -0400,
David T. Lewis wrote:
> 
> Hi Yoshiki,
> 
> Yes, a PipeableOSProcess does require cleanup to close open pipe
> handles. I am away and cannot look at the code right now, but check
> #closePipes, #close, etc. This is not a CogVM or Mac VM issue.
> 
> When running in a CommandShell, the cleanup happens automatically,
> but not when you are interacting directly with an individual
> PipeableOSProcess.
> 
> The resources in question are the unix file handles associated with
> OS pipe endpoints. For example, the standard output from your
> external command is connected to your image via an OS pipe, and
> the reader end of that pipe is represented in your image as a
> file stream. Just as with a file, you need to keep that file stream
> open until you are done using it, and the underlying OS file
> handle does not go away until the file stream is closed.
> 
> The reason that garbage collection does not free up the handles
> is that "OSProcess thisOSProcess allMyChildren" has a dictionary
> of all child processes that have been run, including the PipeableOSProcess
> that you ran. I think that if you empty that dictionary, the
> garbage collection will probably finalize the pipes for you.
> But the better thing to do is close the pipes explicitly.
> 
> Dave
> 
> 
> On Wed, May 16, 2012 at 09:45:55AM -0700, Yoshiki Ohshima wrote:
> > In a fully updated trunk 4.4 alpha image (#12041), load
> > OSProcess-dtl.70 and CommandShell-dtl.61.  And with the latest Cog VM
> > ('Croquet Closure Cog VM [CoInterpreter VMMaker.oscog-eem.157] Croquet
> > Cog 4.0.2550') on MacOS 10.7.4.  If I evaluate:
> > 
> > -------------------------------------
> > v := [1 to: 256 do: [:i |
> > 		(PipeableOSProcess command: 'echo hello') output.
> > 		Transcript print: i; cr.
> > 		(Delay forMilliseconds: 50) wait.]].
> > v fork
> > -------------------------------------
> > 
> > and when i reaches around 242, I get an error that says "cannot create
> > OS pipe" (you actually don't get the reporting to Transcript but...).
> > Garbage collection does not clear the issue (as the comment in
> > #register: of AttachableFileStream suggests).  With lsof, I can see
> > that it keeps all pipes.
> > 
> > Do I need to make some more calls to have them clean up?  (Or, is this
> > another symptom of the file open/close issue with CogVM on Mac VM?)
> > 
> > -- Yoshiki
>