Rcpp: how to use unwind protection?

Question

I was wondering how could I make some Rcpp code use automatic unwind protection in all Rcpp object creations.

For example, suppose I have some code like this:

#include <stdint.h>
#include <Rcpp.h>

class MyObj {
public:
    int val;
    MyObj(int val) : val(val) {};
    ~MyObj() {
        std::cout << "I' being destructed - value was: " << val << std::endl;
    }
};

// [[Rcpp::export]]
Rcpp::NumericVector crashme(unsigned int seed)
{
    srand(seed);
    MyObj obj1(rand());
    Rcpp::NumericVector out(INT64_MAX-1, 100.);
    return out;
}

When I call crashme, obj1 doesn't get destructed before the function ends, due to R's long jumps which I want to protect against.

I see there is a function Rcpp::unwindProtect, but it's implemented as something that takes a callback.

I'm not 100% sure if I'm doing it right, but I managed to add unwind protection like this:

#include <stdint.h>
#include <Rcpp.h>
#include <Rcpp/unwindProtect.h>
// [[Rcpp::plugins(unwindProtect)]]

class MyObj {
public:
    int val;
    MyObj(int val) : val(val) {};
    ~MyObj() {
        std::cout << "I' being destructed - value was: " << val << std::endl;
    }
};

struct NumVecArgs {
    size_t size;
    double fillwith;
};

SEXP alloc_NumVec(void *data)
{
    NumVecArgs *args = (NumVecArgs*)data;
    return Rcpp::NumericVector(args->size, args->fillwith);
}

// [[Rcpp::export]]
Rcpp::NumericVector crashme(unsigned int seed)
{
    srand(seed);
    MyObj obj1(rand());
    NumVecArgs args = {INT64_MAX-1, 100.};
    Rcpp::NumericVector out = Rcpp::unwindProtect(alloc_NumVec, (void*)&args);
    return out;
}

Now calling crashme will successfully destruct obj1 and print the destructor message.

But this is very inconvenient, since I have a series of different Rcpp object allocations taking different constructor types, which would imply either defining a different struct and callback for each one of them, or translating all the calls to lengthy lambda functions.

Is there any way to automatically make all calls to constructors of e.g. Rcpp::NumericVector and Rcpp::IntegerVector have unwind protection?

Answer 1

等待大神答复