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

[Duncan Murdoch]

On 01/04/2021 9:06 p.m., David Cortes wrote:
> 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.

The CRAN policy document is quite clear on this: "CRAN packages should 
use only the public API. Hence they should not use entry points not 
declared as API in installed headers nor .Internal() nor .Call() etc 
calls to base packages. Also, ::: should not be used to access 
undocumented/internal objects in base packages (nor should other means 
of access be employed). Such usages can cause packages to break at any 
time, even in patched versions of R. "

So you are free to use that function, but CRAN won't publish your 
package if you do.

Duncan Murdoch

Duncan Murdoch