[Rd] Crashing R with readline()

Duncan Murdoch murdoch.duncan at gmail.com
Thu Dec 29 22:37:00 CET 2011

On 11-12-29 9:49 AM, Henrik Bengtsson wrote:
> I get the following with R v2.14.1 patched on Windows 7:
> % Rterm --vanilla --silent
>> sessionInfo()
> R version 2.14.1 Patched (2011-12-26 r58001)
> Platform: x86_64-pc-mingw32/x64 (64-bit)
> locale:
> [1] LC_COLLATE=English_United States.1252
> [2] LC_CTYPE=English_United States.1252
> [3] LC_MONETARY=English_United States.1252
> [5] LC_TIME=English_United States.1252
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>> readline(sprintf("%-*s:", 180, "A prompt"))
> A prompt
>                                          :
> [1] ""
>> q("no")
> Error: caught access violation - continue with care
> It is a consistent behavior.

I can reproduce this, but I can't spot where the problem is.  I/O in 
Rterm is very complicated, because we use a getline library that 
implements line editing, and we run the I/O in a thread so that graphics 
windows can be updated while waiting for input.

Presumably the problem is the long prompt causing a buffer overflow 
somewhere, and a workaround is to use a more reasonable length of 
prompt, but I don't think I'm going to be able to offer a real fix.  I'd 
guess this bug is local to Rterm in Windows, but we don't really have 
good tools there to detect buffer overflows.

Duncan Murdoch

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