[R-pkg-devel] Using RC_fopen in a CRAN package

[David Cortes]

I’d like to ask for clarification about CRAN policies regarding usage
of functions that start with "RC_*", such as "RC_fopen".

I'm trying to upload a package which is meant for reading and writing
data from text files in a certain format, for which I want to use a C
file pointer which I obtain through "RC_fopen". The R extensions manual
says the following:
"... there are other header files there that can be included too, but
many of the features they contain should be regarded as undocumented
and unstable."

Since "RC_fopen" is present in a header file, I would guess it should
be classified as "public" within the entry points classification
(between API/public/private/hidden). This is the description for such
entry points in the manual:
"Entry points declared in an installed header file that are exported on
all R platforms but are not documented and subject to change without
notice."

As I understand it, there is nothing that would forbid using public
entry points compared to the explicit point made about "private" entry
points. However, when I try to submit the package to CRAN, it doesn't
make it past the automated checks due to a NOTE:
Check: compiled code, Result: NOTE
  File 'readsparse/libs/readsparse.so':
    Found non-API call to R: 'RC_fopen'
  
  Compiled code should not call non-API entry points in R.
  
  See 'Writing portable packages' in the 'Writing R Extensions' manual.


Is it allowed to use such functions in packages? I see a few packages
currently in CRAN have the same note in the checks, such as "iotools",
and am wondering if I should just email the CRAN maintainer explaining
that I intend to use the function anyway, since it's just a note rather
than a warning or error.