[Rcpp-devel] Possible regression in R-3.2.3 or Rcpp 0.12.3

[Kevin Ushey]

Hmm, I have one thought: we try to re-use the indices from an
IntegerVector, but the type here is actually a sugar type:

    Rcpp::SubsetProxy<13, Rcpp::PreserveStorage, 13, true,
    Rcpp::sugar::Minus_Vector_Primitive<13, true, Rcpp::Vector<13,
    Rcpp::PreserveStorage> > >::get_vec (this=<optimized out>)

Ie, we access the indices with `INTEGER(x)`, but perhaps those indices
have not actually been properly materialized when we attempt to
perform the subset?

But then, a simple test case with `x[y - 1]` with `x` and `y` both
being integer vectors seems to work just fine. So I am a bit confused.

On Fri, Jan 29, 2016 at 3:16 PM, Dirk Eddelbuettel <edd at debian.org> wrote:
>
> On 29 January 2016 at 17:55, Qiang Kou wrote:
> | Hi, Paul, can you try my fork of Rcpp? You can install it by the line below:
> |
> | devtools::install_github("thirdwing/Rcpp", ref = "subsetter")
> |
> | This fixed the segfault on my Ubuntu machine.
>
> Yay. Nice work!
>
> | The difference can be found from [1].
>
> Nice and concise.
>
> | In subsetter, if an IntegerVector passed in, we will try to reuse it. This led
> | to a segfault in this case, which I don't know why.
> |
> | Dirk and Kevin, do you have any thoughts on it?
>
> Not really, but happy to give this the full reverse-dependency check
> treatment so that we can merge it.
>
> Dirk
>
>
> | Best wishes,
> |
> | KK
> |
> | [1] https://github.com/thirdwing/Rcpp/commit/
> | 216c5220bcb84778a656b3496d0f1803b973ef61
> |
> |
> | On Fri, Jan 29, 2016 at 3:00 PM, Qiang Kou <qkou at umail.iu.edu> wrote:
> |
> |
> |     Hi, Kevin, I was also trying to track this down yesterday.
> |
> |     From the debugging info below, indices_n is not equal to length of indices,
> |     which I don't quite understand.
> |
> |     Program received signal SIGSEGV, Segmentation fault.
> |
> |     0x00007ffff2ed5c4e in Rcpp::SubsetProxy<13, Rcpp::PreserveStorage, 13,
> |     true, Rcpp::sugar::Minus_Vector_Primitive<13, true, Rcpp::Vector<13,
> |     Rcpp::PreserveStorage> > >::get_vec (this=this at entry=0x7fffffff79a0)
> |
> |         at /usr/local/lib/R/site-library/Rcpp/include/Rcpp/vector/
> |     Subsetter.h:200
> |
> |     199             output[i] = lhs[ indices[i] ];
> |
> |     (gdb) p i
> |
> |     $1 = 33622
> |
> |     (gdb) p indices[i]
> |
> |     Cannot access memory at address 0x34c6e000
> |
> |     (gdb) p indices_n
> |
> |     $2 = 9594546
> |
> |
> |     On Fri, Jan 29, 2016 at 2:29 PM, Dirk Eddelbuettel <edd at debian.org> wrote:
> |
> |
> |         On 29 January 2016 at 11:27, Kevin Ushey wrote:
> |         | When I add some debug printing to the associated subscripting line
> |         | (https://github.com/awalker89/openxlsx/blob/
> |         b92bb3acdd6ea759be928c298c6faeef2f26fa3e/src/cppFunctions.cpp#L2608),
> |         | I see:
> |         |
> |         |    colNumbers.size(): 98,03,150
> |         |    charCols.size(): 95,94,546
> |         |
> |         | It looks to me like the package is erroneously attempting to subset
> |         | vectors of different sizes, causing out-of-bounds reads.
> |
> |         Nice work.
> |
> |         | Unfortunately, Rcpp is not detecting or warning about this...
> |         |
> |         | Either way, I believe this is a bug in the openxlsx package, but Rcpp
> |         | should be checking / reporting this.
> |
> |         With (Rcpp)Armadillo you do have an option of turning this on/off. With
> |         Rcpp
> |         alone not quite.
> |
> |         Dirk
> |
> |         --
> |         http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org
> |         _______________________________________________
> |         Rcpp-devel mailing list
> |         Rcpp-devel at lists.r-forge.r-project.org
> |         https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
> |
> |
> |
> |
> |     --
> |     Qiang Kou
> |     qkou at umail.iu.edu
> |     School of Informatics and Computing, Indiana University
> |
> |
> |
> |
> |
> | --
> | Qiang Kou
> | qkou at umail.iu.edu
> | School of Informatics and Computing, Indiana University
> |
>
> --
> http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org