[Rcpp-devel] Trouble passing arguments to R functions that have been passed in (maybe)

Hello,

I'm quite new to Rcpp (and R in fact) and I'm having a little bit of 
trouble understanding what is going on in some of my code. I have 
written a fairly small example that exhibits the troublesome behaviour 
using inline (below). The code doesn't do anything interesting, but 
runCode() does cause a "memory not mapped" error. Other times I get an 
"unimplemented type 'NULL' in 'coerceToInteger'" error.

It seems to be the case that sometimes the values N and true do not 
make it back safely to R when calling bar within foo and get 
transformed into NULL or doubles, etc. I still have issues if I 
"PROTECT" their conversion to SEXP via wrap.

I know it is not particularly good to have C++ functions calling R 
functions that have been passed in, but this is a very useful feature 
for me and I have been very happy with Rcpp until this starting 
happening.

Any help on what mistake I've made would be greatly appreciated.

Thanks,
Anthony

Code: (note that removing X and Y seems to make the code more stable)

require(inline)

foo <- cxxfunction(
  signature(N_in = "numeric", n_in = "numeric", bar_in = "function"), 
body='
  BEGIN_RCPP
  int N = as<int>(N_in);
  int n = as<int>(n_in);
  Function bar(bar_in);
  IntegerMatrix A(N,n);
  GenericMatrix X(N,n);
  GenericMatrix Y(N,n);
  A(_,0) = seq_len(N-1);

  for (int i = 1; i < n; i++) {
    A(_,i) = as<IntegerVector>(bar(A(_,i-1),N,true));
  }

  return wrap(A);
  END_RCPP
  ', plugin = "Rcpp" )

translate <- function(size,cond,vs) {
  if (cond) {
    return((vs + 1) %% size)
  } else {
    return((vs - 1) %% size)
  }
}

bar <- function(vs,M,cond) {
  return(translate(size=M,cond=cond,vs=vs))
}

runCode <- function() {
  for (i in 1:5) {
    for (j in 1:10) {
      print(paste(i,j,sep=" "));
      B <- foo(i*100,j*100,bar);
    }
  }
}

# runCode()