[Haskell-cafe] System.Process and -threaded

Donn Cave donn at avvanta.com
Sun May 18 06:25:43 UTC 2014

quoth Karsten Gebbert,
>>     -- mplayer 
>>     (hand,o,e,pid) <- runInteractiveProcess "mplayer" ["-fs", "-idle", "-slave"] Nothing Nothing
>>     putStrLn "listening for commands"
>>     loop sock hand
>>     -- closing everything down
>>     sClose sock
>>     terminateProcess pid
>>     waitForProcess pid
>>     return ()

In an idle moment I wrote up a simplified test program, and found
something interesting.  When compiled with -threaded, the above
code garbage-collects and finalizes "o" -- the child process' output.
That tends to shorten the process life span.

If I build without -threaded, or use "o" during or after the loop,
no problem.  Or if I build with -threaded but run with the -V0 flag,
which I suppose would delay garbage collection.


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