[Rd] Using R_MakeExternalPtr

[Hin-Tak Leung]

As others as commented, everything going in/out of the .Call() interface
needs to be SEXP (even if it does nothing and you are returning
R_NilValue).

Secondly, your attached code is both (1) too long, and (2) incomplete.

You should write some *simple* R code that
uses only soamInit() and soamUnInit() (the latter is missing and you had 
not included it), Then fill the middle with soamSubmit(). Nobody really
want to read your 60+ line of R code (too long) and incomplete C code
(too short) to work out what's broken. Use complete and short examples
to illustrate your problem!

Also, you seem to take for granted that the typo/length of Argument
in soamSubmit() are those you think they are... e.g. I would put in say, 
for example:

if ((JobID == R_NilValue) || ( TYPEOF(JobID) != INTSXP)) {
     Rprintf("JobID unexpected!\n");
     return R_NilValue;
}

Just to be on the safe side. You may find some surprises there -
trying to do INTEGER() on a REALSXP, or vice versa can be dangerous.

I am still not convinced that your segfault is to do with externalptr -
e.g. the '.Call() must return SEXP' is a basic R extension usage and you
didn't understand that one.

Jonathan Zhou wrote:
> Hi all, 
> 
> Here is the R code function in where I called the two C++ and further below
> are the 2 C++ functions I used to create the externalptr and use it : 
> 
> soam.Rapply <- function (x, func, ...,
>                            join.method=cbind,
>                            njobs,
>                            batch.size=100,
>                            packages=NULL,
>                            savelist=NULL)
> {
>     if(missing(njobs))
>         njobs <- max(1,ceiling(nrow(x)/batch.size))
> 
>     if(!is.matrix(x) && !is.data.frame(x))
>         stop("x must be a matrix or data frame")
> 
>     if(njobs>1)
>         {rowSet <- lapply(splitIndices(nrow(x), njobs), function(i) x[i, ,
> drop = FALSE])} else {rowSet <- list(x)}
> 
>     sesCon <- .Call("soamInit")
> 
>     script <- " "
> 
>     fname <- tempfile(pattern = "Rsoam_data", tmpdir = getwd())
>     file(fname, open="w+")
>     if(!is.null(savelist)) {
>         dump(savelist, fname)
>         script<-readLines(fname)
>     }
> 
>     if(!is.null(packages))
>     for(counter in 1:length(packages))
>     {
>         temp<-call("library", packages[counter], character.only=TRUE)
>         dput(temp, fname)
>         pack.call<-readLines(fname)
>         script<-append(script, pack.call)
>     }
> 
>     for(counter in 1:njobs)
>     {
>         caller <- paste("caller", counter, sep = "")
>         soam.call<-call("dput", call("apply", X=rowSet[[counter]], MARGIN=1,
> FUN=func), caller)
>         dput(soam.call, fname)
>         soam.call<-readLines(fname)
> 
>         temp<-append(script, soam.call)
>         final.script = temp[1]
>         for(count in 2:length(temp)){
>             final.script<-paste(final.script, temp[count], "\n")}
> 
>         .Call("soamSubmit", counter, sesCon, final.script, packages)
>     }
> 
>     .Call("soamGetResults", sesCon, njobs, join.method, parent.frame())
> 
>     for(job in 1:njobs)
>     {
>         caller <- paste("result", job, sep = "")
>         temp = dget(caller)
>         if(job==1) {retval=temp} else {retval=join.method(retval,temp)}
>     }
> 
>     .Call("soamUninit")
> 
>     retval
> }
> 
> *** Here are the 2 C++ functions: 
> 
> extern "C"
> {
> SEXP soamInit ()
> {
>     // Initialize the API
>     SoamFactory::initialize();
> 
>     // Set up application specific information to be supplied to Symphony
>     char appName[] = "SampleAppCPP";
> 
>     // Set up application authentication information using the default
> security provider
>     DefaultSecurityCallback securityCB("Guest", "Guest");
> 
>     // Connect to the specified application
>     ConnectionPtr conPtr = SoamFactory::connect(appName, &securityCB);
> 
>     // Set up session creation attributes
>     SessionCreationAttributes attributes;
>     attributes.setSessionName("mySession");
>     attributes.setSessionType("ShortRunningTasks");
>     attributes.setSessionFlags(SF_RECEIVE_SYNC);
> 
>     // Create a synchronous session
>     Session* sesPtr = conPtr->createSession(attributes);
> 
>     SEXP out = R_MakeExternalPtr((void*)temp, R_NilValue, R_NilValue);
> 
>     return out;
> }
> }
> 
> extern "C"
> {
>   void soamSubmit	(SEXP jobID,		//job ID
> 			 SEXP sesCon,		//session pointer
> 			 SEXP caller,			//objects
> 			 SEXP pack)			//packages
> {
> 	char* savelist = CHAR(STRING_ELT(caller, 0));
> 	string strTemp = "";
> 	int job = INTEGER(jobID)[0];
> 
> 	void* temp = R_ExternalPtrAddr(sesCon);
>         Session* sesPtr = reinterpret_cast<Session*>(temp);
> 
>     // Create a message
> 	MyMessage inMsg(job, /*pack,*/ savelist);
> 
>     // Send it
>     TaskInputHandlePtr input = sesPtr->sendTaskInput(&inMsg);
> }
> }