[S] using call_S() from MS Visual C++ to S+ (4.0)

[Suzanne Cashman <scashman@empnet.com>]

Hello, S-users; 

        I have been unsuccessfully trying to implement the call_S() function 
from 
a dll created in MS Visual C++ calling back to S+ (4.0).  Has anyone done 
this sucessfully in this environment?  Other environments? I have been 
trying to get the following simple scenario to work.

>From the output print statement, I know that the program is sucessfully 
entering the c code and passing arguments.  I am unsure of the argument 
casting as online S+ has a different guideline for what should be (void *) 
than the document "Interfacing with C & Fortran Code".  However, I have 
tried each type of casting neither works in my code.

Any assistance would be much appreciated!
-Suzanne

S+ code:

hotel.rpart <- function(y,x){
        z_x+20
        return(as.integer(z))
}

hotel.test <- function(y, n) {

    ret_.C("hotel",
        as.character(list(hotel.rpart)),
        as.double(y),
        as.integer(n))
}



C code:

void hotel(char **function, double *y, int n)
{

        float i = 2;

        char *modes[]= {"double", "single"};
        long lengths[] = {n,1};
        char *names[] = {"y", "i"};

        void *args[2];
        long *result[1];

        args[0] = (void *) y;
        args[1] = (void *) &i;

        printf("function = %s\n", (char *)*function);
        
        call_S((void *) *function, 2L, args, modes, lengths, names, 1L, (char 
**)result);

        printf("exit hotel\n");
}


When I kick this program off with:

inspect(  hotel.test(c(0,1,2,3,4,5,6), 7)  )

I get the following results from the inspector:

> inspect(hotel.test(c(0, 1, 2, 3, 4, 5, 6), 7))
entering function hotel.test
stopped in hotel.test (frame 9), at:
        return(ret <- .C("hotel",
                as.character(list(hotel.rpart)),
                as.double(y),
        ...
d> function = function(y, x)
{
        z <- x + 20
        return(as.integer(z))
}

Calls at time of error:

11: error = function() from 10
10: .C("hotel", from 9
9: hotel.test(c(0, 1, 2, 3, 4, 5, 6), 7) from 1
8: inspect(hotel.test(c(0, 1, 2, 3, 4, 5, 6), 7)) from 1
7: eval(i, local) from 6
6: source(auto.print = auto.print, exprs = substitute(exprs.literal)) from 
5
5: script.run(exprs.literal = { from 1
4: eval(expr, local = F) from 3
3: .Sapi.build.output(txt =  from 2
2: .C(NAME = "S_api_get_message", from 1
1:  from 1

Dumping frames ... Error in .C("hotel",: Function pointer in call to S: bad 
pointer (544868618) for value
Dumped

local frame (frame of error) is .C (frame 10)
d>



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