id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
5212	waitForProcess: does not exist (No child processes)	chrisdone	chrisdone	"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
}}}"	bug	closed	normal		GHC API	6.12.3	worksforme			Linux	x86_64 (amd64)	Incorrect result at runtime