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, LLCTrac 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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