From jorismeys at gmail.com  Thu Aug 18 17:53:42 2011
From: jorismeys at gmail.com (Joris Meys)
Date: Thu, 18 Aug 2011 17:53:42 +0200
Subject: [Rd] problems with connections when applied in tryCatch
Message-ID: <CAO1zAVaQ=uZnp0YZpintN-1XeC+qE3Mqg596fPphnUrVM9FLjg@mail.gmail.com>

Recently on stackoverflow following problem came up :

http://stackoverflow.com/questions/7103429/all-the-connections-are-in-use-execution-halted/7108799#7108799

A reproducible example: When trying

replicate(200,tryCatch(read.table("this.is.no.file"),
          warning=function(w){print(showConnections());print("warning")}))

No connections are shown, but after a number of calls, suddenly the message

Error in file(file, "rt") : all connections are in use

pops up. Trying to get them deleted with closeAllConnections() causes
R to crash on Windows 7. Another user reported a segfault. (see the
link to stackoverflow)

Although I initially thought on.exit() was somehow skipped, that's not
the case. In fact, the connection couldn't be opened, so it can't be
closed either. I have no clue as to why this goes wrong, but it shows
there's something odd happening with the connections. For the record,
I am aware that the use of the warning handler in that call is rather
peculiar. But even then, R shouldn't crash.

Cheers
Joris


-- 
Joris Meys
Statistical consultant

Ghent University
Faculty of Bioscience Engineering
Department of Applied mathematics, biometrics and process control

tel : +32 9 264 59 87
Joris.Meys at Ugent.be
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[Rd] problems with connections when applied in tryCatch
Joris Meys