[Rd] (PR#13487) Segfault when mistakenly calling [.data.frame

[Prof Brian Ripley]

What did your actual application do?  This seems a very strange thing 
to do, and the segfault is in trying to construct the traceback.

Only by using do.call on the object (and not even by name) do I get 
this error.  E.g.

> `[.data.frame`(1:10, 3)
Error in NextMethod("[") : object not specified
> do.call("[.data.frame", list(1:10, 3))
Error in NextMethod("[") : object not specified

are fine.

Obviously it would be nice to fix this, but I'd like to understand the 
actual circumstances: there is more to it than the subject line.

On Thu, 29 Jan 2009, brechbuehler at gmail.com wrote:

> Full_Name: Christian Brechbuehler
> Version: 2.7.2, 2.8.1
> OS: linux-gnu
> Submission from: (NULL) (24.128.51.18)
>
>
> Calling [.data.frame on an object that's not a data frame, specifically 1:10,
> causes segmentation fault.
>
> Context
> =======
> We can subscript with a number of different notations:
>
>   > (1:10)[3]
>   [1] 3
>   > do.call(get("[",pos="package:base"),list(1:10,3))
>   [1] 3
>   > do.call(get("[.numeric_version",pos="package:base"),list(1:10,3))
>   [1] 3
>
> Problem
> =======
> If we mistakenly believe the object is a data frame (as we did in a much more
> complicated real situation), this happens:
>
>   > do.call(get("[.data.frame",pos="package:base"),list(1:10,3))
>   Error in NextMethod("[") :
>     no calling generic was found: was a method called directly?
>
>    *** caught segfault ***
>   address (nil), cause 'unknown'
>
>   Process R:2 segmentation fault (core dumped) at Thu Jan 29 09:26:29 2009
>
> The Error message is appropriate.  But the segmentation fault is unexpected.
>
>
> Versions
> ========
> I reproduced the problem on R 2.7.2 and 2.8.1.  Details:
>
>> version
>               _
> platform       x86_64-unknown-linux-gnu
> arch           x86_64
> os             linux-gnu
> system         x86_64, linux-gnu
> status         Patched
> major          2
> minor          7.2
> year           2008
> month          09
> day            20
> svn rev        46776
> language       R
> version.string R version 2.7.2 Patched (2008-09-20 r46776)
>
> ==========================================================
>
>> version
>               _
> platform       x86_64-unknown-linux-gnu
> arch           x86_64
> os             linux-gnu
> system         x86_64, linux-gnu
> status         Patched
> major          2
> minor          8.1
> year           2009
> month          01
> day            26
> svn rev        47743
> language       R
> version.string R version 2.8.1 Patched (2009-01-26 r47743)
>
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>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595