R devel - Oct 2015 - Error generated by .Internal(nchar) disappears when debugging

Hi all,

I have a puzzling problem related to nchar. In R 3.2.1, the internal nchar
gained an extra argument (see
https://stat.ethz.ch/pipermail/r-announce/2015/000586.html)

I've been testing code using the package copula, and at home I'm still
running R 3.2.0 (I know, I know...). When trying the following code, I got
an error:
> library(copula)
> fgmCopula(0.8)
Error in substr(sc[i], 2, nchar(sc[i]) - 1) :
  4 arguments passed to .Internal(nchar) which requires 3

So I do the obvious and try to debug using debug():
> debugonce(fgmCopula)
> fgmCopula(0.8)
And when I try that, I can step through the complete function without any
error. I know that the obvious solution is to update to R 3.2.2, but :

- I have absolutely no clue how a function can give an error when used
normally, but not return any error when stepping through it using debug.
- The copula package built for R 3.2.2 isn't compatible any longer with R
versions older than R 3.2.1, like the one used in our PC classes. Other
packages might share the same problem.

Can somebody shed some light on what exactly is going on here? I don't want
to bug the authors of the copula package if I'm not sure of the origin of
this problem.

Cheers
Joris
-- 
Joris Meys
Statistical consultant

Ghent University
Faculty of Bioscience Engineering
Department of Mathematical Modelling, Statistics and Bio-Informatics

tel :  +32 (0)9 264 61 79
Joris.Meys at Ugent.be
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Joris Meys <jorismeys <at> gmail.com> writes:
> 
> Hi all,
> 
> I have a puzzling problem related to nchar. In R 3.2.1, the internal 
nchar
> gained an extra argument (see
> https://stat.ethz.ch/pipermail/r-announce/2015/000586.html)
> 
> I've been testing code using the package copula, and at home I'm
still
> running R 3.2.0 (I know, I know...). When trying the following code, I 
got
> an error:
> 
> > library(copula)
> > fgmCopula(0.8)
> Error in substr(sc[i], 2, nchar(sc[i]) - 1) :
>   4 arguments passed to .Internal(nchar) which requires 3
> 
> Cheers
> Joris

I'm seeing a similar problem. IIUC, the Windows binary .zip from CRAN of 
any package using base::nchar is affected. Could someone check my answer 
here is correct please : http://stackoverflow.com/a/32959306/403310

Matt

On 05/10/2015 7:24 PM, Matt Dowle wrote:
> Joris Meys <jorismeys <at> gmail.com> writes:
> 
>>
>> Hi all,
>>
>> I have a puzzling problem related to nchar. In R 3.2.1, the internal 
> nchar
>> gained an extra argument (see
>> https://stat.ethz.ch/pipermail/r-announce/2015/000586.html)
>>
>> I've been testing code using the package copula, and at home
I'm still
>> running R 3.2.0 (I know, I know...). When trying the following code, I 
> got
>> an error:
>>
>>> library(copula)
>>> fgmCopula(0.8)
>> Error in substr(sc[i], 2, nchar(sc[i]) - 1) :
>>   4 arguments passed to .Internal(nchar) which requires 3
>>
>> Cheers
>> Joris
> 
> 
> I'm seeing a similar problem. IIUC, the Windows binary .zip from CRAN
of
> any package using base::nchar is affected. Could someone check my answer 
> here is correct please : http://stackoverflow.com/a/32959306/403310
Nobody has posted a simple reproducible example here, so it's kind of
hard to say.

I would have guessed that a change to the internal signature of the C
code underlying nchar() wouldn't have any effect on a package that
called the R nchar() function.

When I put together my own example (a tiny package containing a function
calling nchar(), built to .zip using R 3.2.2, installed into R 3.2.0),
it confirmed my guess.

On the other hand, if some package is calling the .Internal function
directly, I'd expect that to break.  Packages shouldn't do that.

So I'd say there's been no evidence posted of a problem in R here,
though there may be problems in some of the packages involved.  I'd
welcome an example that provided some usable evidence.

Duncan Murdoch