From whorfin at pixar.com  Fri May 11 23:20:13 2012
From: whorfin at pixar.com (Rick Sayre)
Date: Fri, 11 May 2012 14:20:13 -0700
Subject: [Rd] Passing externalptr to .C()
Message-ID: <4FAD828D.1040707@pixar.com>

Greetings.

2.15.0 added this behavior
http://developer.r-project.org/blosxom.cgi/R-devel/NEWS/2012/03/29#n2012-03-29

     o Passing R objects other than atomic vectors, functions, lists and
       environments to .C() is now deprecated and will give a warning.
       Most cases (especially NULL) are actually coding errors.  NULL
       will be disallowed in future.


This seems to make sense, except that this case includes externalptrs.

I have quite a bit of code, designed to interface with various
external hardware devices, which uses this sort of idiom:

# for example
getDeviceInfo <- function(handle) {
     .C("groovyDevice_getDeviceInfo", PACKAGE="groovyDevice",
	handle,			
	status = as.integer(0))[-1]	# skip handle
}

where "handle" was the result of a .Call to a routine which
returned a SEXP which was the result of a R_MakeExternalPtr() call

The "c" routine looked like:
void
groovyDevice_getDeviceInfo(SEXP handle, int *status)
{
     groovyHandle *gh = R_ExternalPtrAddr(handle);
     *status = GroovyStatus(gh);
}

This all used to work fine.  As of 2.15.0, I now get this:
Warning message:
In getDeviceInfo() :
   passing an object of type 'externalptr' to .C (arg 1) is deprecated

Passing the same handle to a .Call() does [of course] work fine.

I thought my usage was exactly as designed.  How then should I be
passing an externalptr to a .C() call?

Cheers



[Rd] Passing externalptr to .C()
Rick Sayre