[R-pkg-devel] Calling R's tempdir() from C

Dear all,

I want to create a temporary directory from within my C++ R extension.
On the other hand, CRAN's policy dictates that one cannot write anything
outside the boundaries of the session's temporary directory, so I need
to create it exactly there.

The R API offers R_tmpnam and R_tmpnam2, both of which require the path
of the directory where the new name will reside. This can be obtained
using tempdir() in R, but I couldn't find anything similar in the R API.
Am I missing anything too obvious?

I tried out giving a NULL dirname to R_tmpnam{,2}, hoping that even
though it's not mentioned in the docs, they would internally use the
session's tmp dir, but this simply crashed. When embedding R one could
also use the R_TempDir global variable, but this is flagged as
unofficial R API for extensions. Finally, the only solution I could find
was to call the tempdir() R function from within my C++ extension. This
works fine, but it bothers me that there not an equivalent entry point
in R's API.

Any pointers would be appreciated. If I'm deeply misunderstanding
something please also shoot.

Cheers,

Rodrigo