R: C++ Optimization flag when using the inline package

Question

In R when using the cxxfunction from the inline package, how does one change the optimization flag for the cpp compiler?

By default, on my machine, it compiles with

Answer 1

I can suggest a hack. Write a little wrapper program (also called cpp) which calls the real cpp and passes all arguments to it as is except that it passes -O3 for optimization. Then make sure your program occurs first in the executable path resolution for R.

Answer 2

There are a couple of options:

1. The best solution is to modify this for all usage by R so create e.g. a file ~/.R/Makevars and set CFLAGS, CXXFLAGS, ... there. This will affect all use by R CMD INSTALL ..., R CMD SHLIB ... etc pp and as cxxfunction() from inline uses it, it works here too.

2. Specific to inline and Rcpp: modify the plugin, that's why it is a plugin system. See Rcpp:::Rcpp.plugin.maker().

3. Switch back from cxxfunction() to cfunction(), hence do not use a plugin and set all arguments manually.

Needless to say, I like option 1 and use it myself.

Edit: A fourth (and crude !!) method I used to use in the past is to edit $R_HOME/Makeconf and/or Makeconf.site.