[Rcpp-devel] Rcpp::wrap segmentation fault

[Dirk Eddelbuettel]

On 21 November 2010 at 13:46, marc michalewicz wrote:
| Hi,
| 
| I use R 2.12.0 on Fedora FC13 and experience a segmentatioin fault when using a standard example from the artice "Rcpp: Seamless R and C++ integration" by D. Eddelbuettel:
| 
| When trying out this quite small and simple example:
| 
| <snip>
| #include <Rcpp.h>
| 
| int main ()
| {
|   SEXP x;
|   std::vector<std::map<std::string,int> > v;
|   std::map<std::string, int> m1;             
|   std::map<std::string, int> m2;             
|   m1["foo"]=1; m1["bar"]=2;                  
|   m2["foo"]=1; m2["bar"]=2; m2["baz"]=3;     
|                                              
|   v.push_back( m1 );                         
|   v.push_back( m2 );                         
|   x = Rcpp::wrap( v );
| }
| 
| <snip>
| (built with "g++ -g -I/usr/lib64/R/library/Rcpp/include -I/usr/include/R -L/usr/lib64/R/library/Rcpp/lib -lRcpp -Wl,-rpath,/usr/lib64/R/library/Rcpp/lib -lRcpp example.cpp")
| 
| it results in a segmentation fault in libR during the call to wrap.
| 
| What is wrong ? 

Your understanding, mostly.  See the 'Writing R Extentions' manual for an
introduction to writing compiled R functions.

Basically, R itself is the main(). You never see that code. You simply write
functions all confirming to

  SEXP myfunction(SEXP a, SEXP b, ...)

which take one or more SEXP objects and return one SEXP object.  You call
this from as

  val <- .Call("myfunction", list(foo=1:3, bar="ABC"), cumsum(1:100))

which would supply two such arguments (the list and the vector).

Such 'myfunction' functions are now easier to write with Rcpp---as we take of
conversion from/to SEXP and also generally map the SEXP, the representation
of your R objects, to C++ objects. 

There are plenty of examples in the paper Romain and I wrote, here in the
list archives and at other places.  The "inline" package helps you do all
this at the R prompt meaning you do not need to call make, g++, ... yourself.

Hope this helps, Dirk

| Apart from this, my R installation works perfect, anything else too.
| 
| Thanks for any help on this,
| 
| Marc
| 
| 
| 
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-- 
Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com