Platform dependent native routine registration

| Dear All,
| 
| I am trying to convert a package to native routine registration, and
| not sure how to
| best solve the problem of C functions that are only used for a single
| platform, i.e.
| Windows, Linux (& Unix) or macOS.
| 
| If I simply provide a different method table for each platform, then the .Call()
| statements for the other platforms will generate R CMD check warnings,
| both for the
| "undefined" global functions and the registration "problems":
| 
| checking foreign function calls ... WARNING
| Registration problems:
|   symbol ?c_keyring_macos_delete? not in namespace:
|    .Call(c_keyring_macos_delete, utf8(keyring), utf8(service), utf8(username))
|   symbol ?c_keyring_macos_get? not in namespace:
|    .Call(c_keyring_macos_get, utf8(keyring), utf8(service), utf8(username))
| 
| [...]
| 
| See chapter ?System and foreign language interfaces? in the ?Writing R
| Extensions? manual.checking R code for possible problems ... NOTE
| b_macos_delete: no visible binding for global variable
|   ?c_keyring_macos_delete?
| b_macos_get: no visible binding for global variable
|   ?c_keyring_macos_get?
| 
| [...]
| 
| Undefined global functions or variables:
|   c_keyring_macos_create c_keyring_macos_delete
|   c_keyring_macos_delete_keyring c_keyring_macos_get
|   c_keyring_macos_list c_keyring_macos_list_keyring
|   c_keyring_macos_lock_keyring c_keyring_macos_set
|   c_keyring_macos_unlock_keyring
| 
| If possible, I would like to avoid defining dummy functions for all functions
| that are not available on a certain platform, simply because I have a lot of
| them. Is it possible?

Could you resort to preprocessor conditioning to only compile the code
relevant for a particular platform while hiding away the inapplicable parts?

Dirk

http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org