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  • #5212

Closed
Open
Created May 24, 2011 by Chris Done@chrisdoneReporter

waitForProcess: does not exist (No child processes)

I have this error when launching a program on our REHL prod machine.

waitForProcess: does not exist (No child processes)

This is called inside readProcess. I am unable to reproduce it on our REHL dev machine, and my local Ubuntu machine. If I re-implement readProcess with the same source but remove waitForProcess line, I do get standard output. Launching the program is successful.

The problem stems from waitForProcess expecting a process and somehow there isn't one. I didn't think this would be a problem, because waitForProcess itself doesn't throw such an exception, and it *does* handle the process having ended (of course), which is trivial to confirm locally:

λ> (inh,outh,_,pid) <- createProcess (proc "date" [])
Tue May 24 11:19:59 CEST 2011
λ> waitForProcess pid
ExitSuccess
λ>

So perhaps it's in withProcessHandle, which I don't have access to in the Haddock docs. I don't really know what would cause this error. Ideas?

We're using GHC 6.12.3 (I know, not recent). I'd provide a test-case but I can't even reproduce it on my own machine. I don't have direct shell access to the prod machine. The test-case would essentially be "use readProcess", anyway.

I can assign this to me and I'll see if the problem persists when we upgrade to GHC7. FWIW if you want to reproduce the exact case I tried, here it is:

readProcess "pdfinfo" ["--help"] ""
$ pdfinfo -v
pdfinfo version 3.00
Copyright 1996-2004 Glyph & Cog, LLC
Trac metadata
Trac field Value
Version 6.12.3
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component GHC API
Test case
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