We can cause a segmentation violation in R 3.2.2 and R-devel simple by running

runit.Module.client.package.R
runit.modref.R

after one another in a script. There seems to be some interaction with commit r68802 in R itself but after discussion with R Core the best cause of action seems to be to sidestep the issue by not having several test Modules in Rcpp which all define a Module named World.