Wed, 16 Sep 2020

RcppSpdlog 0.0.1: New and Exciting Logging Package

Very thrilled to announce a new package RcppSpdlog which is now on CRAN in its first release 0.0.1. We had tweeted once about the earliest version which had already caught the eyes of Gabi upstream.

RcppSpdlog bundles spdlog, a wonderful header-only C++ logging library with all the bells and whistles you would want that was written by Gabi Melman, and also includes fmt by Victor Zverovic.

I had meant to package this for a few years now but didn’t find an (easy, elegant) way to completely lift stdout / stderr and related uses which R wants us to remove for smoother operations from R itself including synchronized input/output. It was only a few weeks ago that I realized I should subclass a logger (or, more concretely, a sink for a logger) which could then use R input/output. With the right idea the implementaton was easy, and [Gabi](( was most helpful in making sure R CMD check would not see one or two remaining C++ i/o operations (which we currently do by not activating a default logger, and substituing REprintf() in one call). So this is now clean and sween and a simple use is included in an example in the package we can show here too (in slightly shorter form minus the documentation header):

// this portmanteau include also defines the r_sink we use below, and which
// diverts all logging to R via the Rcpp::Rcout replacement for std::cout
#include <RcppSpdlog>

// [[Rcpp::export]]
void exampleRsink() {

    std::string logname = "fromR";                          // fix a name for this logger
    auto sp = spdlog::get(logname);                         // retrieve existing one
    if (sp == nullptr) sp = spdlog::r_sink_mt(logname);     // or create new one if needed

    // change log pattern (changed from [%H:%M:%S %z] [%n] [%^---%L---%$] )
    sp->set_pattern("[%H:%M:%S.%f] [%n] [%^%L%$] [thread %t] %v");

    sp->info("Welcome to spdlog!");
    sp->error("Some error message with arg: {}", 1);

    sp->warn("Easy padding in numbers like {:08d}", 12);
    sp->critical("Support for int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", 42);
    sp->info("Support for floats {:03.2f}", 1.23456);
    sp->info("Positional args are {1} {0}..", "too", "supported");
    sp->info("{:<30}", "left aligned");


The NEWS entry for the first release follows.

Changes in RcppSpdlog version 0.0.1 (2020-09-08)

  • Initial release with added R/Rcpp logging sink example

The only sour grapes, if any, are over the CRAN processing. This was originally uploaded three weeks ago. As a new package, it got extra attention and some truly idiosyncratic attention to two details that were already supplied in the first uploaded version. Yet it needed two rounds of going back and forth for really no great net gain, yet wasting a week each time. I am not all that impressed by this, and not particularly pleased either, but I presume is the “tax” we all pay in order to enjoy the unsurpassed richness of the CRAN repository system which continues to work just flawlessly.

If you like this or other open-source work I do, you can now sponsor me at GitHub. For the first year, GitHub will match your contributions.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.

/code/rcpp | permanent link