[R] iostream (was: is R multi-threaded?)

[Annie Bibble]

In the "Writing extensions for R" document, there is a part that reads:

"Using C++ iostreams, as in this example, is best avoided.  There is no 
guarantee that the output will appear in the R console..."

Does R do anything that would potentially cause a stream:: method in a 
dynamically-loaded library to get stuck waiting for a mutex?  Or is this 
just a warning about potential formatting issues?

(on linux)

Thank you!
Annie