[Rcpp-devel] How to handle std::cout/std::cerr in shared libraries

Watal M. Iwasaki heavy.watal at gmail.com
Fri Oct 26 09:31:13 CEST 2018

Hi all,

I have been working on an R interface package to a shared library written
in C++. It works almost perfectly, but the output to std::cout is not shown
on R console (on Linux). Of course Rcpp::Rcout should be used instead of
std::cout. But in this case I want to let the shared library be pure C++.
So I tried switching the stream buffers in the Rcpp side:
Rcpp::CharacterVector run(const std::vector<std::string>& args) {
    std::streambuf* obuf = std::cout.rdbuf(Rcpp::Rcout.rdbuf());
    mylib::Simulation simulation(args);
    simulation.run(); // std::cout is used in here
    return "something";

It (seemingly) works! But now `devtools::check()` produces 1 note:
❯ checking compiled code ... NOTE
  File ‘mylib/libs/mylib.so’:
    Found ‘__ZNSt3__14coutE’, possibly from ‘std::cout’ (C++)
      Object: ‘run.o’

  Compiled code should not call entry points which might terminate R nor
  write to stdout/stderr instead of to the console, nor use Fortran I/O
  nor system RNGs.

Can I suppress this note? or should I just ignore it? any other good

Watal M. Iwasaki
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