[Rd] Platform dependent native routine registration

[Gábor Csárdi]

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?

Thanks,
Gabor