What are _Rf_cons and _Rf_allocVector3?

Question

I'm working on an R package that uses Rcpp and RcppArmadillo, and I'm trying to profile one of the main functions in the package to improve its runtime.

I'm using gperftools as recommended by Dirk and specifically as described in this blog post. The top two function calls (by number of profiling samples) are called _Rf_cons and _Rf_allocVector3.

Total: 1881 samples
     471  25.0%  25.0%      527  28.0% _Rf_cons
     308  16.4%  41.4%      309  16.4% _Rf_allocVector3

Does anyone know what these functions are, and where they might be called from in Rcpp code? I can't find any references to them via google or in the Rcpp GitHub repo.

Thanks!