allocVector() in C and System.AccessViolationException: Attempted to read or write protected memory ?

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C++/CLI

C

C#

R

Hello, I have a problem with the allocVector () function. I wrote a code (DLL) in C that can be called in R. I would like to call a method of that DLL into my application in C#. The DLL code works fine but when the compiler reaches the next line SEXP Rout = PROTECT (RclustOut = allocVector (INTSXP, 2 * 3));
It gives following exception:
Unhandled exception: System.AccessViolationException: Attempted to read or write protected memory.
The code is as follow:

#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <R.h>
#include <Rinternals.h>
#include <Rmath.h>
#include <R_ext/Applic.h>
#include <R_ext/Lapack.h>
#include <Rdefines.h>

void dividetwo(int a, int b, int *result)
{
*result = a/b;
}
void Rdividetwo(int *a, int *b, int *result)
{
dividetwo(*a, *b, result);
}
#ifdef __cplusplus
extern "C" {
#endif
    void castType(int result, int *sortie)
    {
        SEXP RclustOut, ROut;
        SEXP Rout = PROTECT(RclustOut = allocVector(INTSXP, 2*3));
        PROTECT(ROut = allocVector(VECSXP, 2));
        int *clustOut = INTEGER(RclustOut);

        *sortie = result;

    }

#ifdef __cplusplus
}
#endif