How to generate an R warning safely in Rcpp

r, rcpp, setjmp, warnings

Solution

One of the solutions I came up with involves calling the R's `warning` function from Rcpp:

// [[Rcpp::export]]
void test() {
   Test t;
   Function warning("warning");
   warning("test"); // here R errors are caught and transformed to C++ exceptions
}

which gives the correct behavior if `warn>2`:

start
end
Error in eval(expr, envir, enclos) : (converted from warning) test

I wonder if anybody has a better idea for that.

Problem

We know that calling `Rf_error()` should be avoided in Rcpp as it involves a longjmp over C++ destructors on the stack. This is why we rather throw C++ exceptions in Rcpp code (like `throw Rcpp::exception("...")` or via the `stop("...")` function). However, R warnings may also result in a call to `Rf_error()` (this behavior depends on the `warn` option). So, a call to `Rf_warning()` is also risky. ``` Rcpp::sourceCpp(code = ' #include <Rcpp.h> using namespace Rcpp; class Test { public: Test() { Rcout << "start\\n"; } ~Test() { Rcout << "end\\n"; } }; // [[Rcpp::export]] void test() { Test t; Rf_warning("test"); } ') options(warn=10) test() ## start ## Error in test() : (converted from warning) test ``` We see that the destructor hasn't been called (there's no "end" message). How to generate an R warning in a C++-destructor-friendly way?

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