[Rd] Bug: C-level and _set_rl_word_breaks

Duncan Murdoch murdoch.duncan at gmail.com
Thu Jan 31 14:09:48 CET 2013

On 13-01-30 9:48 PM, Laurent Gautier wrote:
> Hi,
> I filed a bug report in the tracker (id #15169) a short while ago,
> along with a patch, but I came back to it to see that there is
> relatively little movement or participation on the tracker so I
> thought I'd pitch it here (patch attached).
> The function `set_rl_word_breaks` in src/unix/sys-std.c relies on
> statically-allocated strings local to the function, making other C
> code using the readline library, such as a program embedding
> R and using readline as well, at risk of creating a segfault when
> trying to free `rl_basic_word_break_characters` or
> `rl_completer_word_break_characters` when changing them.
> The issue was noticed when embedding R in Python (rpy2); I had an
> ugly hack for a long time (less work than champion the inclusion
> of a patch in R) but the iPython developers pushed what could be
> demanded from the rpy2 with their "R magic" extension and
> so I wrote a patch (and they have made a brittle workaround in
> the meantime).
> The fix would be of interest to anyone embedding R in C and using
> readline (e.g., language interface developers if the language either
> has a console using readline - and chances are that it does - or
> an interface to readline).
> The patch attached is against today's R-dev and will likely apply to
> current R-2.15 branch. With the patch applied, R is building and is
> passing `make check`. It could be slightly expanded by handling
> cases where the calloc() or realloc() faills, although not an absolute
> priority (if allocating 200 bytes fails, the system might have
> bigger worries than keeping R from crashing).

I suspect the reason your bug hasn't been dealt with in the 2 weeks 
since you posted it is that you don't show any code that illustrates the 
problem it causes.  It is much easier to run some code and see that code 
that should be valid is causing a crash, than it is to develop code to 
illustrate it.  Easily illustrated bugs get solved before hard ones.

Your post here gives a lot more detail, but still no code.  This isn't 
an area I'd work on (it seems to be a Unix-only bug), but you might 
attract someone else to look at it if you include a minimal 
self-contained trigger for it.

Duncan Murdoch

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